mtd: nand: Use standard large page OOB layout when using NAND_ECC_NONE

[linux-2.6-block.git] / drivers / mtd / nand / nand_base.c

/*
 *  Overview:
 *   This is the generic MTD driver for NAND flash devices. It should be
 *   capable of working with almost all NAND chips currently available.
 *
 *      Additional technical information is available on
 *      http://www.linux-mtd.infradead.org/doc/nand.html
 *
 *  Copyright (C) 2000 Steven J. Hill (sjhill@realitydiluted.com)
 *                2002-2006 Thomas Gleixner (tglx@linutronix.de)
 *
 *  Credits:
 *      David Woodhouse for adding multichip support
 *
 *      Aleph One Ltd. and Toby Churchill Ltd. for supporting the
 *      rework for 2K page size chips
 *
 *  TODO:
 *      Enable cached programming for 2k page size chips
 *      Check, if mtd->ecctype should be set to MTD_ECC_HW
 *      if we have HW ECC support.
 *      BBT table is not serialized, has to be fixed
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/nmi.h>
#include <linux/types.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/rawnand.h>
#include <linux/mtd/nand_ecc.h>
#include <linux/mtd/nand_bch.h>
#include <linux/interrupt.h>
#include <linux/bitops.h>
#include <linux/io.h>
#include <linux/mtd/partitions.h>
#include <linux/of.h>

static int nand_get_device(struct mtd_info *mtd, int new_state);

static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
                             struct mtd_oob_ops *ops);

/* Define default oob placement schemes for large and small page devices */
static int nand_ooblayout_ecc_sp(struct mtd_info *mtd, int section,
                                 struct mtd_oob_region *oobregion)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;

        if (section > 1)
                return -ERANGE;

        if (!section) {
                oobregion->offset = 0;
                if (mtd->oobsize == 16)
                        oobregion->length = 4;
                else
                        oobregion->length = 3;
        } else {
                if (mtd->oobsize == 8)
                        return -ERANGE;

                oobregion->offset = 6;
                oobregion->length = ecc->total - 4;
        }

        return 0;
}

static int nand_ooblayout_free_sp(struct mtd_info *mtd, int section,
                                  struct mtd_oob_region *oobregion)
{
        if (section > 1)
                return -ERANGE;

        if (mtd->oobsize == 16) {
                if (section)
                        return -ERANGE;

                oobregion->length = 8;
                oobregion->offset = 8;
        } else {
                oobregion->length = 2;
                if (!section)
                        oobregion->offset = 3;
                else
                        oobregion->offset = 6;
        }

        return 0;
}

const struct mtd_ooblayout_ops nand_ooblayout_sp_ops = {
        .ecc = nand_ooblayout_ecc_sp,
        .free = nand_ooblayout_free_sp,
};
EXPORT_SYMBOL_GPL(nand_ooblayout_sp_ops);

static int nand_ooblayout_ecc_lp(struct mtd_info *mtd, int section,
                                 struct mtd_oob_region *oobregion)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;

        if (section || !ecc->total)
                return -ERANGE;

        oobregion->length = ecc->total;
        oobregion->offset = mtd->oobsize - oobregion->length;

        return 0;
}

static int nand_ooblayout_free_lp(struct mtd_info *mtd, int section,
                                  struct mtd_oob_region *oobregion)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;

        if (section)
                return -ERANGE;

        oobregion->length = mtd->oobsize - ecc->total - 2;
        oobregion->offset = 2;

        return 0;
}

const struct mtd_ooblayout_ops nand_ooblayout_lp_ops = {
        .ecc = nand_ooblayout_ecc_lp,
        .free = nand_ooblayout_free_lp,
};
EXPORT_SYMBOL_GPL(nand_ooblayout_lp_ops);

/*
 * Support the old "large page" layout used for 1-bit Hamming ECC where ECC
 * are placed at a fixed offset.
 */
static int nand_ooblayout_ecc_lp_hamming(struct mtd_info *mtd, int section,
                                         struct mtd_oob_region *oobregion)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;

        if (section)
                return -ERANGE;

        switch (mtd->oobsize) {
        case 64:
                oobregion->offset = 40;
                break;
        case 128:
                oobregion->offset = 80;
                break;
        default:
                return -EINVAL;
        }

        oobregion->length = ecc->total;
        if (oobregion->offset + oobregion->length > mtd->oobsize)
                return -ERANGE;

        return 0;
}

static int nand_ooblayout_free_lp_hamming(struct mtd_info *mtd, int section,
                                          struct mtd_oob_region *oobregion)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;
        int ecc_offset = 0;

        if (section < 0 || section > 1)
                return -ERANGE;

        switch (mtd->oobsize) {
        case 64:
                ecc_offset = 40;
                break;
        case 128:
                ecc_offset = 80;
                break;
        default:
                return -EINVAL;
        }

        if (section == 0) {
                oobregion->offset = 2;
                oobregion->length = ecc_offset - 2;
        } else {
                oobregion->offset = ecc_offset + ecc->total;
                oobregion->length = mtd->oobsize - oobregion->offset;
        }

        return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_lp_hamming_ops = {
        .ecc = nand_ooblayout_ecc_lp_hamming,
        .free = nand_ooblayout_free_lp_hamming,
};

static int check_offs_len(struct mtd_info *mtd,
                                        loff_t ofs, uint64_t len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int ret = 0;

        /* Start address must align on block boundary */
        if (ofs & ((1ULL << chip->phys_erase_shift) - 1)) {
                pr_debug("%s: unaligned address\n", __func__);
                ret = -EINVAL;
        }

        /* Length must align on block boundary */
        if (len & ((1ULL << chip->phys_erase_shift) - 1)) {
                pr_debug("%s: length not block aligned\n", __func__);
                ret = -EINVAL;
        }

        return ret;
}

/**
 * nand_release_device - [GENERIC] release chip
 * @mtd: MTD device structure
 *
 * Release chip lock and wake up anyone waiting on the device.
 */
static void nand_release_device(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        /* Release the controller and the chip */
        spin_lock(&chip->controller->lock);
        chip->controller->active = NULL;
        chip->state = FL_READY;
        wake_up(&chip->controller->wq);
        spin_unlock(&chip->controller->lock);
}

/**
 * nand_read_byte - [DEFAULT] read one byte from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 8bit buswidth
 */
static uint8_t nand_read_byte(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        return readb(chip->IO_ADDR_R);
}

/**
 * nand_read_byte16 - [DEFAULT] read one byte endianness aware from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 16bit buswidth with endianness conversion.
 *
 */
static uint8_t nand_read_byte16(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        return (uint8_t) cpu_to_le16(readw(chip->IO_ADDR_R));
}

/**
 * nand_read_word - [DEFAULT] read one word from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 16bit buswidth without endianness conversion.
 */
static u16 nand_read_word(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        return readw(chip->IO_ADDR_R);
}

/**
 * nand_select_chip - [DEFAULT] control CE line
 * @mtd: MTD device structure
 * @chipnr: chipnumber to select, -1 for deselect
 *
 * Default select function for 1 chip devices.
 */
static void nand_select_chip(struct mtd_info *mtd, int chipnr)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        switch (chipnr) {
        case -1:
                chip->cmd_ctrl(mtd, NAND_CMD_NONE, 0 | NAND_CTRL_CHANGE);
                break;
        case 0:
                break;

        default:
                BUG();
        }
}

/**
 * nand_write_byte - [DEFAULT] write single byte to chip
 * @mtd: MTD device structure
 * @byte: value to write
 *
 * Default function to write a byte to I/O[7:0]
 */
static void nand_write_byte(struct mtd_info *mtd, uint8_t byte)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        chip->write_buf(mtd, &byte, 1);
}

/**
 * nand_write_byte16 - [DEFAULT] write single byte to a chip with width 16
 * @mtd: MTD device structure
 * @byte: value to write
 *
 * Default function to write a byte to I/O[7:0] on a 16-bit wide chip.
 */
static void nand_write_byte16(struct mtd_info *mtd, uint8_t byte)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        uint16_t word = byte;

        /*
         * It's not entirely clear what should happen to I/O[15:8] when writing
         * a byte. The ONFi spec (Revision 3.1; 2012-09-19, Section 2.16) reads:
         *
         *    When the host supports a 16-bit bus width, only data is
         *    transferred at the 16-bit width. All address and command line
         *    transfers shall use only the lower 8-bits of the data bus. During
         *    command transfers, the host may place any value on the upper
         *    8-bits of the data bus. During address transfers, the host shall
         *    set the upper 8-bits of the data bus to 00h.
         *
         * One user of the write_byte callback is nand_onfi_set_features. The
         * four parameters are specified to be written to I/O[7:0], but this is
         * neither an address nor a command transfer. Let's assume a 0 on the
         * upper I/O lines is OK.
         */
        chip->write_buf(mtd, (uint8_t *)&word, 2);
}

/**
 * nand_write_buf - [DEFAULT] write buffer to chip
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 *
 * Default write function for 8bit buswidth.
 */
static void nand_write_buf(struct mtd_info *mtd, const uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        iowrite8_rep(chip->IO_ADDR_W, buf, len);
}

/**
 * nand_read_buf - [DEFAULT] read chip data into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 *
 * Default read function for 8bit buswidth.
 */
static void nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        ioread8_rep(chip->IO_ADDR_R, buf, len);
}

/**
 * nand_write_buf16 - [DEFAULT] write buffer to chip
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 *
 * Default write function for 16bit buswidth.
 */
static void nand_write_buf16(struct mtd_info *mtd, const uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        u16 *p = (u16 *) buf;

        iowrite16_rep(chip->IO_ADDR_W, p, len >> 1);
}

/**
 * nand_read_buf16 - [DEFAULT] read chip data into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 *
 * Default read function for 16bit buswidth.
 */
static void nand_read_buf16(struct mtd_info *mtd, uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        u16 *p = (u16 *) buf;

        ioread16_rep(chip->IO_ADDR_R, p, len >> 1);
}

/**
 * nand_block_bad - [DEFAULT] Read bad block marker from the chip
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * Check, if the block is bad.
 */
static int nand_block_bad(struct mtd_info *mtd, loff_t ofs)
{
        int page, page_end, res;
        struct nand_chip *chip = mtd_to_nand(mtd);
        u8 bad;

        if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
                ofs += mtd->erasesize - mtd->writesize;

        page = (int)(ofs >> chip->page_shift) & chip->pagemask;
        page_end = page + (chip->bbt_options & NAND_BBT_SCAN2NDPAGE ? 2 : 1);

        for (; page < page_end; page++) {
                res = chip->ecc.read_oob(mtd, chip, page);
                if (res)
                        return res;

                bad = chip->oob_poi[chip->badblockpos];

                if (likely(chip->badblockbits == 8))
                        res = bad != 0xFF;
                else
                        res = hweight8(bad) < chip->badblockbits;
                if (res)
                        return res;
        }

        return 0;
}

/**
 * nand_default_block_markbad - [DEFAULT] mark a block bad via bad block marker
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * This is the default implementation, which can be overridden by a hardware
 * specific driver. It provides the details for writing a bad block marker to a
 * block.
 */
static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct mtd_oob_ops ops;
        uint8_t buf[2] = { 0, 0 };
        int ret = 0, res, i = 0;

        memset(&ops, 0, sizeof(ops));
        ops.oobbuf = buf;
        ops.ooboffs = chip->badblockpos;
        if (chip->options & NAND_BUSWIDTH_16) {
                ops.ooboffs &= ~0x01;
                ops.len = ops.ooblen = 2;
        } else {
                ops.len = ops.ooblen = 1;
        }
        ops.mode = MTD_OPS_PLACE_OOB;

        /* Write to first/last page(s) if necessary */
        if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
                ofs += mtd->erasesize - mtd->writesize;
        do {
                res = nand_do_write_oob(mtd, ofs, &ops);
                if (!ret)
                        ret = res;

                i++;
                ofs += mtd->writesize;
        } while ((chip->bbt_options & NAND_BBT_SCAN2NDPAGE) && i < 2);

        return ret;
}

/**
 * nand_block_markbad_lowlevel - mark a block bad
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * This function performs the generic NAND bad block marking steps (i.e., bad
 * block table(s) and/or marker(s)). We only allow the hardware driver to
 * specify how to write bad block markers to OOB (chip->block_markbad).
 *
 * We try operations in the following order:
 *
 *  (1) erase the affected block, to allow OOB marker to be written cleanly
 *  (2) write bad block marker to OOB area of affected block (unless flag
 *      NAND_BBT_NO_OOB_BBM is present)
 *  (3) update the BBT
 *
 * Note that we retain the first error encountered in (2) or (3), finish the
 * procedures, and dump the error in the end.
*/
static int nand_block_markbad_lowlevel(struct mtd_info *mtd, loff_t ofs)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int res, ret = 0;

        if (!(chip->bbt_options & NAND_BBT_NO_OOB_BBM)) {
                struct erase_info einfo;

                /* Attempt erase before marking OOB */
                memset(&einfo, 0, sizeof(einfo));
                einfo.mtd = mtd;
                einfo.addr = ofs;
                einfo.len = 1ULL << chip->phys_erase_shift;
                nand_erase_nand(mtd, &einfo, 0);

                /* Write bad block marker to OOB */
                nand_get_device(mtd, FL_WRITING);
                ret = chip->block_markbad(mtd, ofs);
                nand_release_device(mtd);
        }

        /* Mark block bad in BBT */
        if (chip->bbt) {
                res = nand_markbad_bbt(mtd, ofs);
                if (!ret)
                        ret = res;
        }

        if (!ret)
                mtd->ecc_stats.badblocks++;

        return ret;
}

/**
 * nand_check_wp - [GENERIC] check if the chip is write protected
 * @mtd: MTD device structure
 *
 * Check, if the device is write protected. The function expects, that the
 * device is already selected.
 */
static int nand_check_wp(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        /* Broken xD cards report WP despite being writable */
        if (chip->options & NAND_BROKEN_XD)
                return 0;

        /* Check the WP bit */
        chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
        return (chip->read_byte(mtd) & NAND_STATUS_WP) ? 0 : 1;
}

/**
 * nand_block_isreserved - [GENERIC] Check if a block is marked reserved.
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * Check if the block is marked as reserved.
 */
static int nand_block_isreserved(struct mtd_info *mtd, loff_t ofs)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        if (!chip->bbt)
                return 0;
        /* Return info from the table */
        return nand_isreserved_bbt(mtd, ofs);
}

/**
 * nand_block_checkbad - [GENERIC] Check if a block is marked bad
 * @mtd: MTD device structure
 * @ofs: offset from device start
 * @allowbbt: 1, if its allowed to access the bbt area
 *
 * Check, if the block is bad. Either by reading the bad block table or
 * calling of the scan function.
 */
static int nand_block_checkbad(struct mtd_info *mtd, loff_t ofs, int allowbbt)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        if (!chip->bbt)
                return chip->block_bad(mtd, ofs);

        /* Return info from the table */
        return nand_isbad_bbt(mtd, ofs, allowbbt);
}

/**
 * panic_nand_wait_ready - [GENERIC] Wait for the ready pin after commands.
 * @mtd: MTD device structure
 * @timeo: Timeout
 *
 * Helper function for nand_wait_ready used when needing to wait in interrupt
 * context.
 */
static void panic_nand_wait_ready(struct mtd_info *mtd, unsigned long timeo)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int i;

        /* Wait for the device to get ready */
        for (i = 0; i < timeo; i++) {
                if (chip->dev_ready(mtd))
                        break;
                touch_softlockup_watchdog();
                mdelay(1);
        }
}

/**
 * nand_wait_ready - [GENERIC] Wait for the ready pin after commands.
 * @mtd: MTD device structure
 *
 * Wait for the ready pin after a command, and warn if a timeout occurs.
 */
void nand_wait_ready(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        unsigned long timeo = 400;

        if (in_interrupt() || oops_in_progress)
                return panic_nand_wait_ready(mtd, timeo);

        /* Wait until command is processed or timeout occurs */
        timeo = jiffies + msecs_to_jiffies(timeo);
        do {
                if (chip->dev_ready(mtd))
                        return;
                cond_resched();
        } while (time_before(jiffies, timeo));

        if (!chip->dev_ready(mtd))
                pr_warn_ratelimited("timeout while waiting for chip to become ready\n");
}
EXPORT_SYMBOL_GPL(nand_wait_ready);

/**
 * nand_wait_status_ready - [GENERIC] Wait for the ready status after commands.
 * @mtd: MTD device structure
 * @timeo: Timeout in ms
 *
 * Wait for status ready (i.e. command done) or timeout.
 */
static void nand_wait_status_ready(struct mtd_info *mtd, unsigned long timeo)
{
        register struct nand_chip *chip = mtd_to_nand(mtd);

        timeo = jiffies + msecs_to_jiffies(timeo);
        do {
                if ((chip->read_byte(mtd) & NAND_STATUS_READY))
                        break;
                touch_softlockup_watchdog();
        } while (time_before(jiffies, timeo));
};

/**
 * nand_command - [DEFAULT] Send command to NAND device
 * @mtd: MTD device structure
 * @command: the command to be sent
 * @column: the column address for this command, -1 if none
 * @page_addr: the page address for this command, -1 if none
 *
 * Send command to NAND device. This function is used for small page devices
 * (512 Bytes per page).
 */
static void nand_command(struct mtd_info *mtd, unsigned int command,
                         int column, int page_addr)
{
        register struct nand_chip *chip = mtd_to_nand(mtd);
        int ctrl = NAND_CTRL_CLE | NAND_CTRL_CHANGE;

        /* Write out the command to the device */
        if (command == NAND_CMD_SEQIN) {
                int readcmd;

                if (column >= mtd->writesize) {
                        /* OOB area */
                        column -= mtd->writesize;
                        readcmd = NAND_CMD_READOOB;
                } else if (column < 256) {
                        /* First 256 bytes --> READ0 */
                        readcmd = NAND_CMD_READ0;
                } else {
                        column -= 256;
                        readcmd = NAND_CMD_READ1;
                }
                chip->cmd_ctrl(mtd, readcmd, ctrl);
                ctrl &= ~NAND_CTRL_CHANGE;
        }
        chip->cmd_ctrl(mtd, command, ctrl);

        /* Address cycle, when necessary */
        ctrl = NAND_CTRL_ALE | NAND_CTRL_CHANGE;
        /* Serially input address */
        if (column != -1) {
                /* Adjust columns for 16 bit buswidth */
                if (chip->options & NAND_BUSWIDTH_16 &&
                                !nand_opcode_8bits(command))
                        column >>= 1;
                chip->cmd_ctrl(mtd, column, ctrl);
                ctrl &= ~NAND_CTRL_CHANGE;
        }
        if (page_addr != -1) {
                chip->cmd_ctrl(mtd, page_addr, ctrl);
                ctrl &= ~NAND_CTRL_CHANGE;
                chip->cmd_ctrl(mtd, page_addr >> 8, ctrl);
                /* One more address cycle for devices > 32MiB */
                if (chip->chipsize > (32 << 20))
                        chip->cmd_ctrl(mtd, page_addr >> 16, ctrl);
        }
        chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);

        /*
         * Program and erase have their own busy handlers status and sequential
         * in needs no delay
         */
        switch (command) {

        case NAND_CMD_PAGEPROG:
        case NAND_CMD_ERASE1:
        case NAND_CMD_ERASE2:
        case NAND_CMD_SEQIN:
        case NAND_CMD_STATUS:
        case NAND_CMD_READID:
        case NAND_CMD_SET_FEATURES:
                return;

        case NAND_CMD_RESET:
                if (chip->dev_ready)
                        break;
                udelay(chip->chip_delay);
                chip->cmd_ctrl(mtd, NAND_CMD_STATUS,
                               NAND_CTRL_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd,
                               NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);
                /* EZ-NAND can take upto 250ms as per ONFi v4.0 */
                nand_wait_status_ready(mtd, 250);
                return;

                /* This applies to read commands */
        case NAND_CMD_READ0:
                /*
                 * READ0 is sometimes used to exit GET STATUS mode. When this
                 * is the case no address cycles are requested, and we can use
                 * this information to detect that we should not wait for the
                 * device to be ready.
                 */
                if (column == -1 && page_addr == -1)
                        return;

        default:
                /*
                 * If we don't have access to the busy pin, we apply the given
                 * command delay
                 */
                if (!chip->dev_ready) {
                        udelay(chip->chip_delay);
                        return;
                }
        }
        /*
         * Apply this short delay always to ensure that we do wait tWB in
         * any case on any machine.
         */
        ndelay(100);

        nand_wait_ready(mtd);
}

static void nand_ccs_delay(struct nand_chip *chip)
{
        /*
         * The controller already takes care of waiting for tCCS when the RNDIN
         * or RNDOUT command is sent, return directly.
         */
        if (!(chip->options & NAND_WAIT_TCCS))
                return;

        /*
         * Wait tCCS_min if it is correctly defined, otherwise wait 500ns
         * (which should be safe for all NANDs).
         */
        if (chip->data_interface && chip->data_interface->timings.sdr.tCCS_min)
                ndelay(chip->data_interface->timings.sdr.tCCS_min / 1000);
        else
                ndelay(500);
}

/**
 * nand_command_lp - [DEFAULT] Send command to NAND large page device
 * @mtd: MTD device structure
 * @command: the command to be sent
 * @column: the column address for this command, -1 if none
 * @page_addr: the page address for this command, -1 if none
 *
 * Send command to NAND device. This is the version for the new large page
 * devices. We don't have the separate regions as we have in the small page
 * devices. We must emulate NAND_CMD_READOOB to keep the code compatible.
 */
static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
                            int column, int page_addr)
{
        register struct nand_chip *chip = mtd_to_nand(mtd);

        /* Emulate NAND_CMD_READOOB */
        if (command == NAND_CMD_READOOB) {
                column += mtd->writesize;
                command = NAND_CMD_READ0;
        }

        /* Command latch cycle */
        chip->cmd_ctrl(mtd, command, NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);

        if (column != -1 || page_addr != -1) {
                int ctrl = NAND_CTRL_CHANGE | NAND_NCE | NAND_ALE;

                /* Serially input address */
                if (column != -1) {
                        /* Adjust columns for 16 bit buswidth */
                        if (chip->options & NAND_BUSWIDTH_16 &&
                                        !nand_opcode_8bits(command))
                                column >>= 1;
                        chip->cmd_ctrl(mtd, column, ctrl);
                        ctrl &= ~NAND_CTRL_CHANGE;

                        /* Only output a single addr cycle for 8bits opcodes. */
                        if (!nand_opcode_8bits(command))
                                chip->cmd_ctrl(mtd, column >> 8, ctrl);
                }
                if (page_addr != -1) {
                        chip->cmd_ctrl(mtd, page_addr, ctrl);
                        chip->cmd_ctrl(mtd, page_addr >> 8,
                                       NAND_NCE | NAND_ALE);
                        /* One more address cycle for devices > 128MiB */
                        if (chip->chipsize > (128 << 20))
                                chip->cmd_ctrl(mtd, page_addr >> 16,
                                               NAND_NCE | NAND_ALE);
                }
        }
        chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);

        /*
         * Program and erase have their own busy handlers status, sequential
         * in and status need no delay.
         */
        switch (command) {

        case NAND_CMD_CACHEDPROG:
        case NAND_CMD_PAGEPROG:
        case NAND_CMD_ERASE1:
        case NAND_CMD_ERASE2:
        case NAND_CMD_SEQIN:
        case NAND_CMD_STATUS:
        case NAND_CMD_READID:
        case NAND_CMD_SET_FEATURES:
                return;

        case NAND_CMD_RNDIN:
                nand_ccs_delay(chip);
                return;

        case NAND_CMD_RESET:
                if (chip->dev_ready)
                        break;
                udelay(chip->chip_delay);
                chip->cmd_ctrl(mtd, NAND_CMD_STATUS,
                               NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd, NAND_CMD_NONE,
                               NAND_NCE | NAND_CTRL_CHANGE);
                /* EZ-NAND can take upto 250ms as per ONFi v4.0 */
                nand_wait_status_ready(mtd, 250);
                return;

        case NAND_CMD_RNDOUT:
                /* No ready / busy check necessary */
                chip->cmd_ctrl(mtd, NAND_CMD_RNDOUTSTART,
                               NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd, NAND_CMD_NONE,
                               NAND_NCE | NAND_CTRL_CHANGE);

                nand_ccs_delay(chip);
                return;

        case NAND_CMD_READ0:
                /*
                 * READ0 is sometimes used to exit GET STATUS mode. When this
                 * is the case no address cycles are requested, and we can use
                 * this information to detect that READSTART should not be
                 * issued.
                 */
                if (column == -1 && page_addr == -1)
                        return;

                chip->cmd_ctrl(mtd, NAND_CMD_READSTART,
                               NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd, NAND_CMD_NONE,
                               NAND_NCE | NAND_CTRL_CHANGE);

                /* This applies to read commands */
        default:
                /*
                 * If we don't have access to the busy pin, we apply the given
                 * command delay.
                 */
                if (!chip->dev_ready) {
                        udelay(chip->chip_delay);
                        return;
                }
        }

        /*
         * Apply this short delay always to ensure that we do wait tWB in
         * any case on any machine.
         */
        ndelay(100);

        nand_wait_ready(mtd);
}

/**
 * panic_nand_get_device - [GENERIC] Get chip for selected access
 * @chip: the nand chip descriptor
 * @mtd: MTD device structure
 * @new_state: the state which is requested
 *
 * Used when in panic, no locks are taken.
 */
static void panic_nand_get_device(struct nand_chip *chip,
                      struct mtd_info *mtd, int new_state)
{
        /* Hardware controller shared among independent devices */
        chip->controller->active = chip;
        chip->state = new_state;
}

/**
 * nand_get_device - [GENERIC] Get chip for selected access
 * @mtd: MTD device structure
 * @new_state: the state which is requested
 *
 * Get the device and lock it for exclusive access
 */
static int
nand_get_device(struct mtd_info *mtd, int new_state)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        spinlock_t *lock = &chip->controller->lock;
        wait_queue_head_t *wq = &chip->controller->wq;
        DECLARE_WAITQUEUE(wait, current);
retry:
        spin_lock(lock);

        /* Hardware controller shared among independent devices */
        if (!chip->controller->active)
                chip->controller->active = chip;

        if (chip->controller->active == chip && chip->state == FL_READY) {
                chip->state = new_state;
                spin_unlock(lock);
                return 0;
        }
        if (new_state == FL_PM_SUSPENDED) {
                if (chip->controller->active->state == FL_PM_SUSPENDED) {
                        chip->state = FL_PM_SUSPENDED;
                        spin_unlock(lock);
                        return 0;
                }
        }
        set_current_state(TASK_UNINTERRUPTIBLE);
        add_wait_queue(wq, &wait);
        spin_unlock(lock);
        schedule();
        remove_wait_queue(wq, &wait);
        goto retry;
}

/**
 * panic_nand_wait - [GENERIC] wait until the command is done
 * @mtd: MTD device structure
 * @chip: NAND chip structure
 * @timeo: timeout
 *
 * Wait for command done. This is a helper function for nand_wait used when
 * we are in interrupt context. May happen when in panic and trying to write
 * an oops through mtdoops.
 */
static void panic_nand_wait(struct mtd_info *mtd, struct nand_chip *chip,
                            unsigned long timeo)
{
        int i;
        for (i = 0; i < timeo; i++) {
                if (chip->dev_ready) {
                        if (chip->dev_ready(mtd))
                                break;
                } else {
                        if (chip->read_byte(mtd) & NAND_STATUS_READY)
                                break;
                }
                mdelay(1);
        }
}

/**
 * nand_wait - [DEFAULT] wait until the command is done
 * @mtd: MTD device structure
 * @chip: NAND chip structure
 *
 * Wait for command done. This applies to erase and program only.
 */
static int nand_wait(struct mtd_info *mtd, struct nand_chip *chip)
{

        int status;
        unsigned long timeo = 400;

        /*
         * Apply this short delay always to ensure that we do wait tWB in any
         * case on any machine.
         */
        ndelay(100);

        chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);

        if (in_interrupt() || oops_in_progress)
                panic_nand_wait(mtd, chip, timeo);
        else {
                timeo = jiffies + msecs_to_jiffies(timeo);
                do {
                        if (chip->dev_ready) {
                                if (chip->dev_ready(mtd))
                                        break;
                        } else {
                                if (chip->read_byte(mtd) & NAND_STATUS_READY)
                                        break;
                        }
                        cond_resched();
                } while (time_before(jiffies, timeo));
        }

        status = (int)chip->read_byte(mtd);
        /* This can happen if in case of timeout or buggy dev_ready */
        WARN_ON(!(status & NAND_STATUS_READY));
        return status;
}

/**
 * nand_reset_data_interface - Reset data interface and timings
 * @chip: The NAND chip
 * @chipnr: Internal die id
 *
 * Reset the Data interface and timings to ONFI mode 0.
 *
 * Returns 0 for success or negative error code otherwise.
 */
static int nand_reset_data_interface(struct nand_chip *chip, int chipnr)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        const struct nand_data_interface *conf;
        int ret;

        if (!chip->setup_data_interface)
                return 0;

        /*
         * The ONFI specification says:
         * "
         * To transition from NV-DDR or NV-DDR2 to the SDR data
         * interface, the host shall use the Reset (FFh) command
         * using SDR timing mode 0. A device in any timing mode is
         * required to recognize Reset (FFh) command issued in SDR
         * timing mode 0.
         * "
         *
         * Configure the data interface in SDR mode and set the
         * timings to timing mode 0.
         */

        conf = nand_get_default_data_interface();
        ret = chip->setup_data_interface(mtd, chipnr, conf);
        if (ret)
                pr_err("Failed to configure data interface to SDR timing mode 0\n");

        return ret;
}

/**
 * nand_setup_data_interface - Setup the best data interface and timings
 * @chip: The NAND chip
 * @chipnr: Internal die id
 *
 * Find and configure the best data interface and NAND timings supported by
 * the chip and the driver.
 * First tries to retrieve supported timing modes from ONFI information,
 * and if the NAND chip does not support ONFI, relies on the
 * ->onfi_timing_mode_default specified in the nand_ids table.
 *
 * Returns 0 for success or negative error code otherwise.
 */
static int nand_setup_data_interface(struct nand_chip *chip, int chipnr)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        int ret;

        if (!chip->setup_data_interface || !chip->data_interface)
                return 0;

        /*
         * Ensure the timing mode has been changed on the chip side
         * before changing timings on the controller side.
         */
        if (chip->onfi_version &&
            (le16_to_cpu(chip->onfi_params.opt_cmd) &
             ONFI_OPT_CMD_SET_GET_FEATURES)) {
                u8 tmode_param[ONFI_SUBFEATURE_PARAM_LEN] = {
                        chip->onfi_timing_mode_default,
                };

                ret = chip->onfi_set_features(mtd, chip,
                                ONFI_FEATURE_ADDR_TIMING_MODE,
                                tmode_param);
                if (ret)
                        goto err;
        }

        ret = chip->setup_data_interface(mtd, chipnr, chip->data_interface);
err:
        return ret;
}

/**
 * nand_init_data_interface - find the best data interface and timings
 * @chip: The NAND chip
 *
 * Find the best data interface and NAND timings supported by the chip
 * and the driver.
 * First tries to retrieve supported timing modes from ONFI information,
 * and if the NAND chip does not support ONFI, relies on the
 * ->onfi_timing_mode_default specified in the nand_ids table. After this
 * function nand_chip->data_interface is initialized with the best timing mode
 * available.
 *
 * Returns 0 for success or negative error code otherwise.
 */
static int nand_init_data_interface(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        int modes, mode, ret;

        if (!chip->setup_data_interface)
                return 0;

        /*
         * First try to identify the best timings from ONFI parameters and
         * if the NAND does not support ONFI, fallback to the default ONFI
         * timing mode.
         */
        modes = onfi_get_async_timing_mode(chip);
        if (modes == ONFI_TIMING_MODE_UNKNOWN) {
                if (!chip->onfi_timing_mode_default)
                        return 0;

                modes = GENMASK(chip->onfi_timing_mode_default, 0);
        }

        chip->data_interface = kzalloc(sizeof(*chip->data_interface),
                                       GFP_KERNEL);
        if (!chip->data_interface)
                return -ENOMEM;

        for (mode = fls(modes) - 1; mode >= 0; mode--) {
                ret = onfi_init_data_interface(chip, chip->data_interface,
                                               NAND_SDR_IFACE, mode);
                if (ret)
                        continue;

                /* Pass -1 to only */
                ret = chip->setup_data_interface(mtd,
                                                 NAND_DATA_IFACE_CHECK_ONLY,
                                                 chip->data_interface);
                if (!ret) {
                        chip->onfi_timing_mode_default = mode;
                        break;
                }
        }

        return 0;
}

static void nand_release_data_interface(struct nand_chip *chip)
{
        kfree(chip->data_interface);
}

/**
 * nand_reset - Reset and initialize a NAND device
 * @chip: The NAND chip
 * @chipnr: Internal die id
 *
 * Returns 0 for success or negative error code otherwise
 */
int nand_reset(struct nand_chip *chip, int chipnr)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        int ret;

        ret = nand_reset_data_interface(chip, chipnr);
        if (ret)
                return ret;

        /*
         * The CS line has to be released before we can apply the new NAND
         * interface settings, hence this weird ->select_chip() dance.
         */
        chip->select_chip(mtd, chipnr);
        chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
        chip->select_chip(mtd, -1);

        chip->select_chip(mtd, chipnr);
        ret = nand_setup_data_interface(chip, chipnr);
        chip->select_chip(mtd, -1);
        if (ret)
                return ret;

        return 0;
}

/**
 * nand_check_erased_buf - check if a buffer contains (almost) only 0xff data
 * @buf: buffer to test
 * @len: buffer length
 * @bitflips_threshold: maximum number of bitflips
 *
 * Check if a buffer contains only 0xff, which means the underlying region
 * has been erased and is ready to be programmed.
 * The bitflips_threshold specify the maximum number of bitflips before
 * considering the region is not erased.
 * Note: The logic of this function has been extracted from the memweight
 * implementation, except that nand_check_erased_buf function exit before
 * testing the whole buffer if the number of bitflips exceed the
 * bitflips_threshold value.
 *
 * Returns a positive number of bitflips less than or equal to
 * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
 * threshold.
 */
static int nand_check_erased_buf(void *buf, int len, int bitflips_threshold)
{
        const unsigned char *bitmap = buf;
        int bitflips = 0;
        int weight;

        for (; len && ((uintptr_t)bitmap) % sizeof(long);
             len--, bitmap++) {
                weight = hweight8(*bitmap);
                bitflips += BITS_PER_BYTE - weight;
                if (unlikely(bitflips > bitflips_threshold))
                        return -EBADMSG;
        }

        for (; len >= sizeof(long);
             len -= sizeof(long), bitmap += sizeof(long)) {
                unsigned long d = *((unsigned long *)bitmap);
                if (d == ~0UL)
                        continue;
                weight = hweight_long(d);
                bitflips += BITS_PER_LONG - weight;
                if (unlikely(bitflips > bitflips_threshold))
                        return -EBADMSG;
        }

        for (; len > 0; len--, bitmap++) {
                weight = hweight8(*bitmap);
                bitflips += BITS_PER_BYTE - weight;
                if (unlikely(bitflips > bitflips_threshold))
                        return -EBADMSG;
        }

        return bitflips;
}

/**
 * nand_check_erased_ecc_chunk - check if an ECC chunk contains (almost) only
 *                               0xff data
 * @data: data buffer to test
 * @datalen: data length
 * @ecc: ECC buffer
 * @ecclen: ECC length
 * @extraoob: extra OOB buffer
 * @extraooblen: extra OOB length
 * @bitflips_threshold: maximum number of bitflips
 *
 * Check if a data buffer and its associated ECC and OOB data contains only
 * 0xff pattern, which means the underlying region has been erased and is
 * ready to be programmed.
 * The bitflips_threshold specify the maximum number of bitflips before
 * considering the region as not erased.
 *
 * Note:
 * 1/ ECC algorithms are working on pre-defined block sizes which are usually
 *    different from the NAND page size. When fixing bitflips, ECC engines will
 *    report the number of errors per chunk, and the NAND core infrastructure
 *    expect you to return the maximum number of bitflips for the whole page.
 *    This is why you should always use this function on a single chunk and
 *    not on the whole page. After checking each chunk you should update your
 *    max_bitflips value accordingly.
 * 2/ When checking for bitflips in erased pages you should not only check
 *    the payload data but also their associated ECC data, because a user might
 *    have programmed almost all bits to 1 but a few. In this case, we
 *    shouldn't consider the chunk as erased, and checking ECC bytes prevent
 *    this case.
 * 3/ The extraoob argument is optional, and should be used if some of your OOB
 *    data are protected by the ECC engine.
 *    It could also be used if you support subpages and want to attach some
 *    extra OOB data to an ECC chunk.
 *
 * Returns a positive number of bitflips less than or equal to
 * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
 * threshold. In case of success, the passed buffers are filled with 0xff.
 */
int nand_check_erased_ecc_chunk(void *data, int datalen,
                                void *ecc, int ecclen,
                                void *extraoob, int extraooblen,
                                int bitflips_threshold)
{
        int data_bitflips = 0, ecc_bitflips = 0, extraoob_bitflips = 0;

        data_bitflips = nand_check_erased_buf(data, datalen,
                                              bitflips_threshold);
        if (data_bitflips < 0)
                return data_bitflips;

        bitflips_threshold -= data_bitflips;

        ecc_bitflips = nand_check_erased_buf(ecc, ecclen, bitflips_threshold);
        if (ecc_bitflips < 0)
                return ecc_bitflips;

        bitflips_threshold -= ecc_bitflips;

        extraoob_bitflips = nand_check_erased_buf(extraoob, extraooblen,
                                                  bitflips_threshold);
        if (extraoob_bitflips < 0)
                return extraoob_bitflips;

        if (data_bitflips)
                memset(data, 0xff, datalen);

        if (ecc_bitflips)
                memset(ecc, 0xff, ecclen);

        if (extraoob_bitflips)
                memset(extraoob, 0xff, extraooblen);

        return data_bitflips + ecc_bitflips + extraoob_bitflips;
}
EXPORT_SYMBOL(nand_check_erased_ecc_chunk);

/**
 * nand_read_page_raw - [INTERN] read raw page data without ecc
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Not for syndrome calculating ECC controllers, which use a special oob layout.
 */
int nand_read_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
                       uint8_t *buf, int oob_required, int page)
{
        chip->read_buf(mtd, buf, mtd->writesize);
        if (oob_required)
                chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        return 0;
}
EXPORT_SYMBOL(nand_read_page_raw);

/**
 * nand_read_page_raw_syndrome - [INTERN] read raw page data without ecc
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * We need a special oob layout and handling even when OOB isn't used.
 */
static int nand_read_page_raw_syndrome(struct mtd_info *mtd,
                                       struct nand_chip *chip, uint8_t *buf,
                                       int oob_required, int page)
{
        int eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        uint8_t *oob = chip->oob_poi;
        int steps, size;

        for (steps = chip->ecc.steps; steps > 0; steps--) {
                chip->read_buf(mtd, buf, eccsize);
                buf += eccsize;

                if (chip->ecc.prepad) {
                        chip->read_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->read_buf(mtd, oob, eccbytes);
                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->read_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }
        }

        size = mtd->oobsize - (oob - chip->oob_poi);
        if (size)
                chip->read_buf(mtd, oob, size);

        return 0;
}

/**
 * nand_read_page_swecc - [REPLACEABLE] software ECC based page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 */
static int nand_read_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
                                uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size, ret;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *p = buf;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        uint8_t *ecc_code = chip->buffers->ecccode;
        unsigned int max_bitflips = 0;

        chip->ecc.read_page_raw(mtd, chip, buf, 1, page);

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize)
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);

        ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
                                         chip->ecc.total);
        if (ret)
                return ret;

        eccsteps = chip->ecc.steps;
        p = buf;

        for (i = 0 ; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_subpage - [REPLACEABLE] ECC based sub-page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @data_offs: offset of requested data within the page
 * @readlen: data length
 * @bufpoi: buffer to store read data
 * @page: page number to read
 */
static int nand_read_subpage(struct mtd_info *mtd, struct nand_chip *chip,
                        uint32_t data_offs, uint32_t readlen, uint8_t *bufpoi,
                        int page)
{
        int start_step, end_step, num_steps, ret;
        uint8_t *p;
        int data_col_addr, i, gaps = 0;
        int datafrag_len, eccfrag_len, aligned_len, aligned_pos;
        int busw = (chip->options & NAND_BUSWIDTH_16) ? 2 : 1;
        int index, section = 0;
        unsigned int max_bitflips = 0;
        struct mtd_oob_region oobregion = { };

        /* Column address within the page aligned to ECC size (256bytes) */
        start_step = data_offs / chip->ecc.size;
        end_step = (data_offs + readlen - 1) / chip->ecc.size;
        num_steps = end_step - start_step + 1;
        index = start_step * chip->ecc.bytes;

        /* Data size aligned to ECC ecc.size */
        datafrag_len = num_steps * chip->ecc.size;
        eccfrag_len = num_steps * chip->ecc.bytes;

        data_col_addr = start_step * chip->ecc.size;
        /* If we read not a page aligned data */
        if (data_col_addr != 0)
                chip->cmdfunc(mtd, NAND_CMD_RNDOUT, data_col_addr, -1);

        p = bufpoi + data_col_addr;
        chip->read_buf(mtd, p, datafrag_len);

        /* Calculate ECC */
        for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size)
                chip->ecc.calculate(mtd, p, &chip->buffers->ecccalc[i]);

        /*
         * The performance is faster if we position offsets according to
         * ecc.pos. Let's make sure that there are no gaps in ECC positions.
         */
        ret = mtd_ooblayout_find_eccregion(mtd, index, &section, &oobregion);
        if (ret)
                return ret;

        if (oobregion.length < eccfrag_len)
                gaps = 1;

        if (gaps) {
                chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize, -1);
                chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        } else {
                /*
                 * Send the command to read the particular ECC bytes take care
                 * about buswidth alignment in read_buf.
                 */
                aligned_pos = oobregion.offset & ~(busw - 1);
                aligned_len = eccfrag_len;
                if (oobregion.offset & (busw - 1))
                        aligned_len++;
                if ((oobregion.offset + (num_steps * chip->ecc.bytes)) &
                    (busw - 1))
                        aligned_len++;

                chip->cmdfunc(mtd, NAND_CMD_RNDOUT,
                              mtd->writesize + aligned_pos, -1);
                chip->read_buf(mtd, &chip->oob_poi[aligned_pos], aligned_len);
        }

        ret = mtd_ooblayout_get_eccbytes(mtd, chip->buffers->ecccode,
                                         chip->oob_poi, index, eccfrag_len);
        if (ret)
                return ret;

        p = bufpoi + data_col_addr;
        for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size) {
                int stat;

                stat = chip->ecc.correct(mtd, p,
                        &chip->buffers->ecccode[i], &chip->buffers->ecccalc[i]);
                if (stat == -EBADMSG &&
                    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
                        /* check for empty pages with bitflips */
                        stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
                                                &chip->buffers->ecccode[i],
                                                chip->ecc.bytes,
                                                NULL, 0,
                                                chip->ecc.strength);
                }

                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_page_hwecc - [REPLACEABLE] hardware ECC based page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Not for syndrome calculating ECC controllers which need a special oob layout.
 */
static int nand_read_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
                                uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size, ret;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *p = buf;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        uint8_t *ecc_code = chip->buffers->ecccode;
        unsigned int max_bitflips = 0;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                chip->ecc.hwctl(mtd, NAND_ECC_READ);
                chip->read_buf(mtd, p, eccsize);
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);
        }
        chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);

        ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
                                         chip->ecc.total);
        if (ret)
                return ret;

        eccsteps = chip->ecc.steps;
        p = buf;

        for (i = 0 ; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
                if (stat == -EBADMSG &&
                    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
                        /* check for empty pages with bitflips */
                        stat = nand_check_erased_ecc_chunk(p, eccsize,
                                                &ecc_code[i], eccbytes,
                                                NULL, 0,
                                                chip->ecc.strength);
                }

                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_page_hwecc_oob_first - [REPLACEABLE] hw ecc, read oob first
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Hardware ECC for large page chips, require OOB to be read first. For this
 * ECC mode, the write_page method is re-used from ECC_HW. These methods
 * read/write ECC from the OOB area, unlike the ECC_HW_SYNDROME support with
 * multiple ECC steps, follows the "infix ECC" scheme and reads/writes ECC from
 * the data area, by overwriting the NAND manufacturer bad block markings.
 */
static int nand_read_page_hwecc_oob_first(struct mtd_info *mtd,
        struct nand_chip *chip, uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size, ret;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *p = buf;
        uint8_t *ecc_code = chip->buffers->ecccode;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        unsigned int max_bitflips = 0;

        /* Read the OOB area first */
        chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
        chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);

        ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
                                         chip->ecc.total);
        if (ret)
                return ret;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                chip->ecc.hwctl(mtd, NAND_ECC_READ);
                chip->read_buf(mtd, p, eccsize);
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);

                stat = chip->ecc.correct(mtd, p, &ecc_code[i], NULL);
                if (stat == -EBADMSG &&
                    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
                        /* check for empty pages with bitflips */
                        stat = nand_check_erased_ecc_chunk(p, eccsize,
                                                &ecc_code[i], eccbytes,
                                                NULL, 0,
                                                chip->ecc.strength);
                }

                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page read
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * The hw generator calculates the error syndrome automatically. Therefore we
 * need a special oob layout and handling.
 */
static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
                                   uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        int eccpadbytes = eccbytes + chip->ecc.prepad + chip->ecc.postpad;
        uint8_t *p = buf;
        uint8_t *oob = chip->oob_poi;
        unsigned int max_bitflips = 0;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                chip->ecc.hwctl(mtd, NAND_ECC_READ);
                chip->read_buf(mtd, p, eccsize);

                if (chip->ecc.prepad) {
                        chip->read_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->ecc.hwctl(mtd, NAND_ECC_READSYN);
                chip->read_buf(mtd, oob, eccbytes);
                stat = chip->ecc.correct(mtd, p, oob, NULL);

                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->read_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }

                if (stat == -EBADMSG &&
                    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
                        /* check for empty pages with bitflips */
                        stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
                                                           oob - eccpadbytes,
                                                           eccpadbytes,
                                                           NULL, 0,
                                                           chip->ecc.strength);
                }

                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }

        /* Calculate remaining oob bytes */
        i = mtd->oobsize - (oob - chip->oob_poi);
        if (i)
                chip->read_buf(mtd, oob, i);

        return max_bitflips;
}

/**
 * nand_transfer_oob - [INTERN] Transfer oob to client buffer
 * @mtd: mtd info structure
 * @oob: oob destination address
 * @ops: oob ops structure
 * @len: size of oob to transfer
 */
static uint8_t *nand_transfer_oob(struct mtd_info *mtd, uint8_t *oob,
                                  struct mtd_oob_ops *ops, size_t len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int ret;

        switch (ops->mode) {

        case MTD_OPS_PLACE_OOB:
        case MTD_OPS_RAW:
                memcpy(oob, chip->oob_poi + ops->ooboffs, len);
                return oob + len;

        case MTD_OPS_AUTO_OOB:
                ret = mtd_ooblayout_get_databytes(mtd, oob, chip->oob_poi,
                                                  ops->ooboffs, len);
                BUG_ON(ret);
                return oob + len;

        default:
                BUG();
        }
        return NULL;
}

/**
 * nand_setup_read_retry - [INTERN] Set the READ RETRY mode
 * @mtd: MTD device structure
 * @retry_mode: the retry mode to use
 *
 * Some vendors supply a special command to shift the Vt threshold, to be used
 * when there are too many bitflips in a page (i.e., ECC error). After setting
 * a new threshold, the host should retry reading the page.
 */
static int nand_setup_read_retry(struct mtd_info *mtd, int retry_mode)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        pr_debug("setting READ RETRY mode %d\n", retry_mode);

        if (retry_mode >= chip->read_retries)
                return -EINVAL;

        if (!chip->setup_read_retry)
                return -EOPNOTSUPP;

        return chip->setup_read_retry(mtd, retry_mode);
}

/**
 * nand_do_read_ops - [INTERN] Read data with ECC
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob ops structure
 *
 * Internal function. Called with chip held.
 */
static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                            struct mtd_oob_ops *ops)
{
        int chipnr, page, realpage, col, bytes, aligned, oob_required;
        struct nand_chip *chip = mtd_to_nand(mtd);
        int ret = 0;
        uint32_t readlen = ops->len;
        uint32_t oobreadlen = ops->ooblen;
        uint32_t max_oobsize = mtd_oobavail(mtd, ops);

        uint8_t *bufpoi, *oob, *buf;
        int use_bufpoi;
        unsigned int max_bitflips = 0;
        int retry_mode = 0;
        bool ecc_fail = false;

        chipnr = (int)(from >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        realpage = (int)(from >> chip->page_shift);
        page = realpage & chip->pagemask;

        col = (int)(from & (mtd->writesize - 1));

        buf = ops->datbuf;
        oob = ops->oobbuf;
        oob_required = oob ? 1 : 0;

        while (1) {
                unsigned int ecc_failures = mtd->ecc_stats.failed;

                bytes = min(mtd->writesize - col, readlen);
                aligned = (bytes == mtd->writesize);

                if (!aligned)
                        use_bufpoi = 1;
                else if (chip->options & NAND_USE_BOUNCE_BUFFER)
                        use_bufpoi = !virt_addr_valid(buf) ||
                                     !IS_ALIGNED((unsigned long)buf,
                                                 chip->buf_align);
                else
                        use_bufpoi = 0;

                /* Is the current page in the buffer? */
                if (realpage != chip->pagebuf || oob) {
                        bufpoi = use_bufpoi ? chip->buffers->databuf : buf;

                        if (use_bufpoi && aligned)
                                pr_debug("%s: using read bounce buffer for buf@%p\n",
                                                 __func__, buf);

read_retry:
                        if (nand_standard_page_accessors(&chip->ecc))
                                chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);

                        /*
                         * Now read the page into the buffer.  Absent an error,
                         * the read methods return max bitflips per ecc step.
                         */
                        if (unlikely(ops->mode == MTD_OPS_RAW))
                                ret = chip->ecc.read_page_raw(mtd, chip, bufpoi,
                                                              oob_required,
                                                              page);
                        else if (!aligned && NAND_HAS_SUBPAGE_READ(chip) &&
                                 !oob)
                                ret = chip->ecc.read_subpage(mtd, chip,
                                                        col, bytes, bufpoi,
                                                        page);
                        else
                                ret = chip->ecc.read_page(mtd, chip, bufpoi,
                                                          oob_required, page);
                        if (ret < 0) {
                                if (use_bufpoi)
                                        /* Invalidate page cache */
                                        chip->pagebuf = -1;
                                break;
                        }

                        /* Transfer not aligned data */
                        if (use_bufpoi) {
                                if (!NAND_HAS_SUBPAGE_READ(chip) && !oob &&
                                    !(mtd->ecc_stats.failed - ecc_failures) &&
                                    (ops->mode != MTD_OPS_RAW)) {
                                        chip->pagebuf = realpage;
                                        chip->pagebuf_bitflips = ret;
                                } else {
                                        /* Invalidate page cache */
                                        chip->pagebuf = -1;
                                }
                                memcpy(buf, chip->buffers->databuf + col, bytes);
                        }

                        if (unlikely(oob)) {
                                int toread = min(oobreadlen, max_oobsize);

                                if (toread) {
                                        oob = nand_transfer_oob(mtd,
                                                oob, ops, toread);
                                        oobreadlen -= toread;
                                }
                        }

                        if (chip->options & NAND_NEED_READRDY) {
                                /* Apply delay or wait for ready/busy pin */
                                if (!chip->dev_ready)
                                        udelay(chip->chip_delay);
                                else
                                        nand_wait_ready(mtd);
                        }

                        if (mtd->ecc_stats.failed - ecc_failures) {
                                if (retry_mode + 1 < chip->read_retries) {
                                        retry_mode++;
                                        ret = nand_setup_read_retry(mtd,
                                                        retry_mode);
                                        if (ret < 0)
                                                break;

                                        /* Reset failures; retry */
                                        mtd->ecc_stats.failed = ecc_failures;
                                        goto read_retry;
                                } else {
                                        /* No more retry modes; real failure */
                                        ecc_fail = true;
                                }
                        }

                        buf += bytes;
                        max_bitflips = max_t(unsigned int, max_bitflips, ret);
                } else {
                        memcpy(buf, chip->buffers->databuf + col, bytes);
                        buf += bytes;
                        max_bitflips = max_t(unsigned int, max_bitflips,
                                             chip->pagebuf_bitflips);
                }

                readlen -= bytes;

                /* Reset to retry mode 0 */
                if (retry_mode) {
                        ret = nand_setup_read_retry(mtd, 0);
                        if (ret < 0)
                                break;
                        retry_mode = 0;
                }

                if (!readlen)
                        break;

                /* For subsequent reads align to page boundary */
                col = 0;
                /* Increment page address */
                realpage++;

                page = realpage & chip->pagemask;
                /* Check, if we cross a chip boundary */
                if (!page) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }
        chip->select_chip(mtd, -1);

        ops->retlen = ops->len - (size_t) readlen;
        if (oob)
                ops->oobretlen = ops->ooblen - oobreadlen;

        if (ret < 0)
                return ret;

        if (ecc_fail)
                return -EBADMSG;

        return max_bitflips;
}

/**
 * nand_read - [MTD Interface] MTD compatibility function for nand_do_read_ecc
 * @mtd: MTD device structure
 * @from: offset to read from
 * @len: number of bytes to read
 * @retlen: pointer to variable to store the number of read bytes
 * @buf: the databuffer to put data
 *
 * Get hold of the chip and call nand_do_read.
 */
static int nand_read(struct mtd_info *mtd, loff_t from, size_t len,
                     size_t *retlen, uint8_t *buf)
{
        struct mtd_oob_ops ops;
        int ret;

        nand_get_device(mtd, FL_READING);
        memset(&ops, 0, sizeof(ops));
        ops.len = len;
        ops.datbuf = buf;
        ops.mode = MTD_OPS_PLACE_OOB;
        ret = nand_do_read_ops(mtd, from, &ops);
        *retlen = ops.retlen;
        nand_release_device(mtd);
        return ret;
}

/**
 * nand_read_oob_std - [REPLACEABLE] the most common OOB data read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to read
 */
int nand_read_oob_std(struct mtd_info *mtd, struct nand_chip *chip, int page)
{
        chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
        chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        return 0;
}
EXPORT_SYMBOL(nand_read_oob_std);

/**
 * nand_read_oob_syndrome - [REPLACEABLE] OOB data read function for HW ECC
 *                          with syndromes
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to read
 */
int nand_read_oob_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
                           int page)
{
        int length = mtd->oobsize;
        int chunk = chip->ecc.bytes + chip->ecc.prepad + chip->ecc.postpad;
        int eccsize = chip->ecc.size;
        uint8_t *bufpoi = chip->oob_poi;
        int i, toread, sndrnd = 0, pos;

        chip->cmdfunc(mtd, NAND_CMD_READ0, chip->ecc.size, page);
        for (i = 0; i < chip->ecc.steps; i++) {
                if (sndrnd) {
                        pos = eccsize + i * (eccsize + chunk);
                        if (mtd->writesize > 512)
                                chip->cmdfunc(mtd, NAND_CMD_RNDOUT, pos, -1);
                        else
                                chip->cmdfunc(mtd, NAND_CMD_READ0, pos, page);
                } else
                        sndrnd = 1;
                toread = min_t(int, length, chunk);
                chip->read_buf(mtd, bufpoi, toread);
                bufpoi += toread;
                length -= toread;
        }
        if (length > 0)
                chip->read_buf(mtd, bufpoi, length);

        return 0;
}
EXPORT_SYMBOL(nand_read_oob_syndrome);

/**
 * nand_write_oob_std - [REPLACEABLE] the most common OOB data write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to write
 */
int nand_write_oob_std(struct mtd_info *mtd, struct nand_chip *chip, int page)
{
        int status = 0;
        const uint8_t *buf = chip->oob_poi;
        int length = mtd->oobsize;

        chip->cmdfunc(mtd, NAND_CMD_SEQIN, mtd->writesize, page);
        chip->write_buf(mtd, buf, length);
        /* Send command to program the OOB data */
        chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

        status = chip->waitfunc(mtd, chip);

        return status & NAND_STATUS_FAIL ? -EIO : 0;
}
EXPORT_SYMBOL(nand_write_oob_std);

/**
 * nand_write_oob_syndrome - [REPLACEABLE] OOB data write function for HW ECC
 *                           with syndrome - only for large page flash
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to write
 */
int nand_write_oob_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
                            int page)
{
        int chunk = chip->ecc.bytes + chip->ecc.prepad + chip->ecc.postpad;
        int eccsize = chip->ecc.size, length = mtd->oobsize;
        int i, len, pos, status = 0, sndcmd = 0, steps = chip->ecc.steps;
        const uint8_t *bufpoi = chip->oob_poi;

        /*
         * data-ecc-data-ecc ... ecc-oob
         * or
         * data-pad-ecc-pad-data-pad .... ecc-pad-oob
         */
        if (!chip->ecc.prepad && !chip->ecc.postpad) {
                pos = steps * (eccsize + chunk);
                steps = 0;
        } else
                pos = eccsize;

        chip->cmdfunc(mtd, NAND_CMD_SEQIN, pos, page);
        for (i = 0; i < steps; i++) {
                if (sndcmd) {
                        if (mtd->writesize <= 512) {
                                uint32_t fill = 0xFFFFFFFF;

                                len = eccsize;
                                while (len > 0) {
                                        int num = min_t(int, len, 4);
                                        chip->write_buf(mtd, (uint8_t *)&fill,
                                                        num);
                                        len -= num;
                                }
                        } else {
                                pos = eccsize + i * (eccsize + chunk);
                                chip->cmdfunc(mtd, NAND_CMD_RNDIN, pos, -1);
                        }
                } else
                        sndcmd = 1;
                len = min_t(int, length, chunk);
                chip->write_buf(mtd, bufpoi, len);
                bufpoi += len;
                length -= len;
        }
        if (length > 0)
                chip->write_buf(mtd, bufpoi, length);

        chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
        status = chip->waitfunc(mtd, chip);

        return status & NAND_STATUS_FAIL ? -EIO : 0;
}
EXPORT_SYMBOL(nand_write_oob_syndrome);

/**
 * nand_do_read_oob - [INTERN] NAND read out-of-band
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob operations description structure
 *
 * NAND read out-of-band data from the spare area.
 */
static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
                            struct mtd_oob_ops *ops)
{
        int page, realpage, chipnr;
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct mtd_ecc_stats stats;
        int readlen = ops->ooblen;
        int len;
        uint8_t *buf = ops->oobbuf;
        int ret = 0;

        pr_debug("%s: from = 0x%08Lx, len = %i\n",
                        __func__, (unsigned long long)from, readlen);

        stats = mtd->ecc_stats;

        len = mtd_oobavail(mtd, ops);

        if (unlikely(ops->ooboffs >= len)) {
                pr_debug("%s: attempt to start read outside oob\n",
                                __func__);
                return -EINVAL;
        }

        /* Do not allow reads past end of device */
        if (unlikely(from >= mtd->size ||
                     ops->ooboffs + readlen > ((mtd->size >> chip->page_shift) -
                                        (from >> chip->page_shift)) * len)) {
                pr_debug("%s: attempt to read beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        chipnr = (int)(from >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        /* Shift to get page */
        realpage = (int)(from >> chip->page_shift);
        page = realpage & chip->pagemask;

        while (1) {
                if (ops->mode == MTD_OPS_RAW)
                        ret = chip->ecc.read_oob_raw(mtd, chip, page);
                else
                        ret = chip->ecc.read_oob(mtd, chip, page);

                if (ret < 0)
                        break;

                len = min(len, readlen);
                buf = nand_transfer_oob(mtd, buf, ops, len);

                if (chip->options & NAND_NEED_READRDY) {
                        /* Apply delay or wait for ready/busy pin */
                        if (!chip->dev_ready)
                                udelay(chip->chip_delay);
                        else
                                nand_wait_ready(mtd);
                }

                readlen -= len;
                if (!readlen)
                        break;

                /* Increment page address */
                realpage++;

                page = realpage & chip->pagemask;
                /* Check, if we cross a chip boundary */
                if (!page) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }
        chip->select_chip(mtd, -1);

        ops->oobretlen = ops->ooblen - readlen;

        if (ret < 0)
                return ret;

        if (mtd->ecc_stats.failed - stats.failed)
                return -EBADMSG;

        return  mtd->ecc_stats.corrected - stats.corrected ? -EUCLEAN : 0;
}

/**
 * nand_read_oob - [MTD Interface] NAND read data and/or out-of-band
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob operation description structure
 *
 * NAND read data and/or out-of-band data.
 */
static int nand_read_oob(struct mtd_info *mtd, loff_t from,
                         struct mtd_oob_ops *ops)
{
        int ret;

        ops->retlen = 0;

        /* Do not allow reads past end of device */
        if (ops->datbuf && (from + ops->len) > mtd->size) {
                pr_debug("%s: attempt to read beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        if (ops->mode != MTD_OPS_PLACE_OOB &&
            ops->mode != MTD_OPS_AUTO_OOB &&
            ops->mode != MTD_OPS_RAW)
                return -ENOTSUPP;

        nand_get_device(mtd, FL_READING);

        if (!ops->datbuf)
                ret = nand_do_read_oob(mtd, from, ops);
        else
                ret = nand_do_read_ops(mtd, from, ops);

        nand_release_device(mtd);
        return ret;
}


/**
 * nand_write_page_raw - [INTERN] raw page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * Not for syndrome calculating ECC controllers, which use a special oob layout.
 */
int nand_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
                        const uint8_t *buf, int oob_required, int page)
{
        chip->write_buf(mtd, buf, mtd->writesize);
        if (oob_required)
                chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);

        return 0;
}
EXPORT_SYMBOL(nand_write_page_raw);

/**
 * nand_write_page_raw_syndrome - [INTERN] raw page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * We need a special oob layout and handling even when ECC isn't checked.
 */
static int nand_write_page_raw_syndrome(struct mtd_info *mtd,
                                        struct nand_chip *chip,
                                        const uint8_t *buf, int oob_required,
                                        int page)
{
        int eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        uint8_t *oob = chip->oob_poi;
        int steps, size;

        for (steps = chip->ecc.steps; steps > 0; steps--) {
                chip->write_buf(mtd, buf, eccsize);
                buf += eccsize;

                if (chip->ecc.prepad) {
                        chip->write_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->write_buf(mtd, oob, eccbytes);
                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->write_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }
        }

        size = mtd->oobsize - (oob - chip->oob_poi);
        if (size)
                chip->write_buf(mtd, oob, size);

        return 0;
}
/**
 * nand_write_page_swecc - [REPLACEABLE] software ECC based page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
                                 const uint8_t *buf, int oob_required,
                                 int page)
{
        int i, eccsize = chip->ecc.size, ret;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        const uint8_t *p = buf;

        /* Software ECC calculation */
        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize)
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);

        ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc, chip->oob_poi, 0,
                                         chip->ecc.total);
        if (ret)
                return ret;

        return chip->ecc.write_page_raw(mtd, chip, buf, 1, page);
}

/**
 * nand_write_page_hwecc - [REPLACEABLE] hardware ECC based page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
                                  const uint8_t *buf, int oob_required,
                                  int page)
{
        int i, eccsize = chip->ecc.size, ret;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        const uint8_t *p = buf;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                chip->ecc.hwctl(mtd, NAND_ECC_WRITE);
                chip->write_buf(mtd, p, eccsize);
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);
        }

        ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc, chip->oob_poi, 0,
                                         chip->ecc.total);
        if (ret)
                return ret;

        chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);

        return 0;
}


/**
 * nand_write_subpage_hwecc - [REPLACEABLE] hardware ECC based subpage write
 * @mtd:        mtd info structure
 * @chip:       nand chip info structure
 * @offset:     column address of subpage within the page
 * @data_len:   data length
 * @buf:        data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_subpage_hwecc(struct mtd_info *mtd,
                                struct nand_chip *chip, uint32_t offset,
                                uint32_t data_len, const uint8_t *buf,
                                int oob_required, int page)
{
        uint8_t *oob_buf  = chip->oob_poi;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        int ecc_size      = chip->ecc.size;
        int ecc_bytes     = chip->ecc.bytes;
        int ecc_steps     = chip->ecc.steps;
        uint32_t start_step = offset / ecc_size;
        uint32_t end_step   = (offset + data_len - 1) / ecc_size;
        int oob_bytes       = mtd->oobsize / ecc_steps;
        int step, ret;

        for (step = 0; step < ecc_steps; step++) {
                /* configure controller for WRITE access */
                chip->ecc.hwctl(mtd, NAND_ECC_WRITE);

                /* write data (untouched subpages already masked by 0xFF) */
                chip->write_buf(mtd, buf, ecc_size);

                /* mask ECC of un-touched subpages by padding 0xFF */
                if ((step < start_step) || (step > end_step))
                        memset(ecc_calc, 0xff, ecc_bytes);
                else
                        chip->ecc.calculate(mtd, buf, ecc_calc);

                /* mask OOB of un-touched subpages by padding 0xFF */
                /* if oob_required, preserve OOB metadata of written subpage */
                if (!oob_required || (step < start_step) || (step > end_step))
                        memset(oob_buf, 0xff, oob_bytes);

                buf += ecc_size;
                ecc_calc += ecc_bytes;
                oob_buf  += oob_bytes;
        }

        /* copy calculated ECC for whole page to chip->buffer->oob */
        /* this include masked-value(0xFF) for unwritten subpages */
        ecc_calc = chip->buffers->ecccalc;
        ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc, chip->oob_poi, 0,
                                         chip->ecc.total);
        if (ret)
                return ret;

        /* write OOB buffer to NAND device */
        chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);

        return 0;
}


/**
 * nand_write_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page write
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * The hw generator calculates the error syndrome automatically. Therefore we
 * need a special oob layout and handling.
 */
static int nand_write_page_syndrome(struct mtd_info *mtd,
                                    struct nand_chip *chip,
                                    const uint8_t *buf, int oob_required,
                                    int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        const uint8_t *p = buf;
        uint8_t *oob = chip->oob_poi;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {

                chip->ecc.hwctl(mtd, NAND_ECC_WRITE);
                chip->write_buf(mtd, p, eccsize);

                if (chip->ecc.prepad) {
                        chip->write_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->ecc.calculate(mtd, p, oob);
                chip->write_buf(mtd, oob, eccbytes);
                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->write_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }
        }

        /* Calculate remaining oob bytes */
        i = mtd->oobsize - (oob - chip->oob_poi);
        if (i)
                chip->write_buf(mtd, oob, i);

        return 0;
}

/**
 * nand_write_page - write one page
 * @mtd: MTD device structure
 * @chip: NAND chip descriptor
 * @offset: address offset within the page
 * @data_len: length of actual data to be written
 * @buf: the data to write
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 * @raw: use _raw version of write_page
 */
static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
                uint32_t offset, int data_len, const uint8_t *buf,
                int oob_required, int page, int raw)
{
        int status, subpage;

        if (!(chip->options & NAND_NO_SUBPAGE_WRITE) &&
                chip->ecc.write_subpage)
                subpage = offset || (data_len < mtd->writesize);
        else
                subpage = 0;

        if (nand_standard_page_accessors(&chip->ecc))
                chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);

        if (unlikely(raw))
                status = chip->ecc.write_page_raw(mtd, chip, buf,
                                                  oob_required, page);
        else if (subpage)
                status = chip->ecc.write_subpage(mtd, chip, offset, data_len,
                                                 buf, oob_required, page);
        else
                status = chip->ecc.write_page(mtd, chip, buf, oob_required,
                                              page);

        if (status < 0)
                return status;

        if (nand_standard_page_accessors(&chip->ecc)) {
                chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

                status = chip->waitfunc(mtd, chip);
                if (status & NAND_STATUS_FAIL)
                        return -EIO;
        }

        return 0;
}

/**
 * nand_fill_oob - [INTERN] Transfer client buffer to oob
 * @mtd: MTD device structure
 * @oob: oob data buffer
 * @len: oob data write length
 * @ops: oob ops structure
 */
static uint8_t *nand_fill_oob(struct mtd_info *mtd, uint8_t *oob, size_t len,
                              struct mtd_oob_ops *ops)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int ret;

        /*
         * Initialise to all 0xFF, to avoid the possibility of left over OOB
         * data from a previous OOB read.
         */
        memset(chip->oob_poi, 0xff, mtd->oobsize);

        switch (ops->mode) {

        case MTD_OPS_PLACE_OOB:
        case MTD_OPS_RAW:
                memcpy(chip->oob_poi + ops->ooboffs, oob, len);
                return oob + len;

        case MTD_OPS_AUTO_OOB:
                ret = mtd_ooblayout_set_databytes(mtd, oob, chip->oob_poi,
                                                  ops->ooboffs, len);
                BUG_ON(ret);
                return oob + len;

        default:
                BUG();
        }
        return NULL;
}

#define NOTALIGNED(x)   ((x & (chip->subpagesize - 1)) != 0)

/**
 * nand_do_write_ops - [INTERN] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operations description structure
 *
 * NAND write with ECC.
 */
static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
                             struct mtd_oob_ops *ops)
{
        int chipnr, realpage, page, blockmask, column;
        struct nand_chip *chip = mtd_to_nand(mtd);
        uint32_t writelen = ops->len;

        uint32_t oobwritelen = ops->ooblen;
        uint32_t oobmaxlen = mtd_oobavail(mtd, ops);

        uint8_t *oob = ops->oobbuf;
        uint8_t *buf = ops->datbuf;
        int ret;
        int oob_required = oob ? 1 : 0;

        ops->retlen = 0;
        if (!writelen)
                return 0;

        /* Reject writes, which are not page aligned */
        if (NOTALIGNED(to) || NOTALIGNED(ops->len)) {
                pr_notice("%s: attempt to write non page aligned data\n",
                           __func__);
                return -EINVAL;
        }

        column = to & (mtd->writesize - 1);

        chipnr = (int)(to >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        /* Check, if it is write protected */
        if (nand_check_wp(mtd)) {
                ret = -EIO;
                goto err_out;
        }

        realpage = (int)(to >> chip->page_shift);
        page = realpage & chip->pagemask;
        blockmask = (1 << (chip->phys_erase_shift - chip->page_shift)) - 1;

        /* Invalidate the page cache, when we write to the cached page */
        if (to <= ((loff_t)chip->pagebuf << chip->page_shift) &&
            ((loff_t)chip->pagebuf << chip->page_shift) < (to + ops->len))
                chip->pagebuf = -1;

        /* Don't allow multipage oob writes with offset */
        if (oob && ops->ooboffs && (ops->ooboffs + ops->ooblen > oobmaxlen)) {
                ret = -EINVAL;
                goto err_out;
        }

        while (1) {
                int bytes = mtd->writesize;
                uint8_t *wbuf = buf;
                int use_bufpoi;
                int part_pagewr = (column || writelen < mtd->writesize);

                if (part_pagewr)
                        use_bufpoi = 1;
                else if (chip->options & NAND_USE_BOUNCE_BUFFER)
                        use_bufpoi = !virt_addr_valid(buf) ||
                                     !IS_ALIGNED((unsigned long)buf,
                                                 chip->buf_align);
                else
                        use_bufpoi = 0;

                /* Partial page write?, or need to use bounce buffer */
                if (use_bufpoi) {
                        pr_debug("%s: using write bounce buffer for buf@%p\n",
                                         __func__, buf);
                        if (part_pagewr)
                                bytes = min_t(int, bytes - column, writelen);
                        chip->pagebuf = -1;
                        memset(chip->buffers->databuf, 0xff, mtd->writesize);
                        memcpy(&chip->buffers->databuf[column], buf, bytes);
                        wbuf = chip->buffers->databuf;
                }

                if (unlikely(oob)) {
                        size_t len = min(oobwritelen, oobmaxlen);
                        oob = nand_fill_oob(mtd, oob, len, ops);
                        oobwritelen -= len;
                } else {
                        /* We still need to erase leftover OOB data */
                        memset(chip->oob_poi, 0xff, mtd->oobsize);
                }

                ret = nand_write_page(mtd, chip, column, bytes, wbuf,
                                      oob_required, page,
                                      (ops->mode == MTD_OPS_RAW));
                if (ret)
                        break;

                writelen -= bytes;
                if (!writelen)
                        break;

                column = 0;
                buf += bytes;
                realpage++;

                page = realpage & chip->pagemask;
                /* Check, if we cross a chip boundary */
                if (!page) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }

        ops->retlen = ops->len - writelen;
        if (unlikely(oob))
                ops->oobretlen = ops->ooblen;

err_out:
        chip->select_chip(mtd, -1);
        return ret;
}

/**
 * panic_nand_write - [MTD Interface] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @len: number of bytes to write
 * @retlen: pointer to variable to store the number of written bytes
 * @buf: the data to write
 *
 * NAND write with ECC. Used when performing writes in interrupt context, this
 * may for example be called by mtdoops when writing an oops while in panic.
 */
static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
                            size_t *retlen, const uint8_t *buf)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct mtd_oob_ops ops;
        int ret;

        /* Wait for the device to get ready */
        panic_nand_wait(mtd, chip, 400);

        /* Grab the device */
        panic_nand_get_device(chip, mtd, FL_WRITING);

        memset(&ops, 0, sizeof(ops));
        ops.len = len;
        ops.datbuf = (uint8_t *)buf;
        ops.mode = MTD_OPS_PLACE_OOB;

        ret = nand_do_write_ops(mtd, to, &ops);

        *retlen = ops.retlen;
        return ret;
}

/**
 * nand_write - [MTD Interface] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @len: number of bytes to write
 * @retlen: pointer to variable to store the number of written bytes
 * @buf: the data to write
 *
 * NAND write with ECC.
 */
static int nand_write(struct mtd_info *mtd, loff_t to, size_t len,
                          size_t *retlen, const uint8_t *buf)
{
        struct mtd_oob_ops ops;
        int ret;

        nand_get_device(mtd, FL_WRITING);
        memset(&ops, 0, sizeof(ops));
        ops.len = len;
        ops.datbuf = (uint8_t *)buf;
        ops.mode = MTD_OPS_PLACE_OOB;
        ret = nand_do_write_ops(mtd, to, &ops);
        *retlen = ops.retlen;
        nand_release_device(mtd);
        return ret;
}

/**
 * nand_do_write_oob - [MTD Interface] NAND write out-of-band
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operation description structure
 *
 * NAND write out-of-band.
 */
static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
                             struct mtd_oob_ops *ops)
{
        int chipnr, page, status, len;
        struct nand_chip *chip = mtd_to_nand(mtd);

        pr_debug("%s: to = 0x%08x, len = %i\n",
                         __func__, (unsigned int)to, (int)ops->ooblen);

        len = mtd_oobavail(mtd, ops);

        /* Do not allow write past end of page */
        if ((ops->ooboffs + ops->ooblen) > len) {
                pr_debug("%s: attempt to write past end of page\n",
                                __func__);
                return -EINVAL;
        }

        if (unlikely(ops->ooboffs >= len)) {
                pr_debug("%s: attempt to start write outside oob\n",
                                __func__);
                return -EINVAL;
        }

        /* Do not allow write past end of device */
        if (unlikely(to >= mtd->size ||
                     ops->ooboffs + ops->ooblen >
                        ((mtd->size >> chip->page_shift) -
                         (to >> chip->page_shift)) * len)) {
                pr_debug("%s: attempt to write beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        chipnr = (int)(to >> chip->chip_shift);

        /*
         * Reset the chip. Some chips (like the Toshiba TC5832DC found in one
         * of my DiskOnChip 2000 test units) will clear the whole data page too
         * if we don't do this. I have no clue why, but I seem to have 'fixed'
         * it in the doc2000 driver in August 1999.  dwmw2.
         */
        nand_reset(chip, chipnr);

        chip->select_chip(mtd, chipnr);

        /* Shift to get page */
        page = (int)(to >> chip->page_shift);

        /* Check, if it is write protected */
        if (nand_check_wp(mtd)) {
                chip->select_chip(mtd, -1);
                return -EROFS;
        }

        /* Invalidate the page cache, if we write to the cached page */
        if (page == chip->pagebuf)
                chip->pagebuf = -1;

        nand_fill_oob(mtd, ops->oobbuf, ops->ooblen, ops);

        if (ops->mode == MTD_OPS_RAW)
                status = chip->ecc.write_oob_raw(mtd, chip, page & chip->pagemask);
        else
                status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);

        chip->select_chip(mtd, -1);

        if (status)
                return status;

        ops->oobretlen = ops->ooblen;

        return 0;
}

/**
 * nand_write_oob - [MTD Interface] NAND write data and/or out-of-band
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operation description structure
 */
static int nand_write_oob(struct mtd_info *mtd, loff_t to,
                          struct mtd_oob_ops *ops)
{
        int ret = -ENOTSUPP;

        ops->retlen = 0;

        /* Do not allow writes past end of device */
        if (ops->datbuf && (to + ops->len) > mtd->size) {
                pr_debug("%s: attempt to write beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        nand_get_device(mtd, FL_WRITING);

        switch (ops->mode) {
        case MTD_OPS_PLACE_OOB:
        case MTD_OPS_AUTO_OOB:
        case MTD_OPS_RAW:
                break;

        default:
                goto out;
        }

        if (!ops->datbuf)
                ret = nand_do_write_oob(mtd, to, ops);
        else
                ret = nand_do_write_ops(mtd, to, ops);

out:
        nand_release_device(mtd);
        return ret;
}

/**
 * single_erase - [GENERIC] NAND standard block erase command function
 * @mtd: MTD device structure
 * @page: the page address of the block which will be erased
 *
 * Standard erase command for NAND chips. Returns NAND status.
 */
static int single_erase(struct mtd_info *mtd, int page)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        /* Send commands to erase a block */
        chip->cmdfunc(mtd, NAND_CMD_ERASE1, -1, page);
        chip->cmdfunc(mtd, NAND_CMD_ERASE2, -1, -1);

        return chip->waitfunc(mtd, chip);
}

/**
 * nand_erase - [MTD Interface] erase block(s)
 * @mtd: MTD device structure
 * @instr: erase instruction
 *
 * Erase one ore more blocks.
 */
static int nand_erase(struct mtd_info *mtd, struct erase_info *instr)
{
        return nand_erase_nand(mtd, instr, 0);
}

/**
 * nand_erase_nand - [INTERN] erase block(s)
 * @mtd: MTD device structure
 * @instr: erase instruction
 * @allowbbt: allow erasing the bbt area
 *
 * Erase one ore more blocks.
 */
int nand_erase_nand(struct mtd_info *mtd, struct erase_info *instr,
                    int allowbbt)
{
        int page, status, pages_per_block, ret, chipnr;
        struct nand_chip *chip = mtd_to_nand(mtd);
        loff_t len;

        pr_debug("%s: start = 0x%012llx, len = %llu\n",
                        __func__, (unsigned long long)instr->addr,
                        (unsigned long long)instr->len);

        if (check_offs_len(mtd, instr->addr, instr->len))
                return -EINVAL;

        /* Grab the lock and see if the device is available */
        nand_get_device(mtd, FL_ERASING);

        /* Shift to get first page */
        page = (int)(instr->addr >> chip->page_shift);
        chipnr = (int)(instr->addr >> chip->chip_shift);

        /* Calculate pages in each block */
        pages_per_block = 1 << (chip->phys_erase_shift - chip->page_shift);

        /* Select the NAND device */
        chip->select_chip(mtd, chipnr);

        /* Check, if it is write protected */
        if (nand_check_wp(mtd)) {
                pr_debug("%s: device is write protected!\n",
                                __func__);
                instr->state = MTD_ERASE_FAILED;
                goto erase_exit;
        }

        /* Loop through the pages */
        len = instr->len;

        instr->state = MTD_ERASING;

        while (len) {
                /* Check if we have a bad block, we do not erase bad blocks! */
                if (nand_block_checkbad(mtd, ((loff_t) page) <<
                                        chip->page_shift, allowbbt)) {
                        pr_warn("%s: attempt to erase a bad block at page 0x%08x\n",
                                    __func__, page);
                        instr->state = MTD_ERASE_FAILED;
                        goto erase_exit;
                }

                /*
                 * Invalidate the page cache, if we erase the block which
                 * contains the current cached page.
                 */
                if (page <= chip->pagebuf && chip->pagebuf <
                    (page + pages_per_block))
                        chip->pagebuf = -1;

                status = chip->erase(mtd, page & chip->pagemask);

                /* See if block erase succeeded */
                if (status & NAND_STATUS_FAIL) {
                        pr_debug("%s: failed erase, page 0x%08x\n",
                                        __func__, page);
                        instr->state = MTD_ERASE_FAILED;
                        instr->fail_addr =
                                ((loff_t)page << chip->page_shift);
                        goto erase_exit;
                }

                /* Increment page address and decrement length */
                len -= (1ULL << chip->phys_erase_shift);
                page += pages_per_block;

                /* Check, if we cross a chip boundary */
                if (len && !(page & chip->pagemask)) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }
        instr->state = MTD_ERASE_DONE;

erase_exit:

        ret = instr->state == MTD_ERASE_DONE ? 0 : -EIO;

        /* Deselect and wake up anyone waiting on the device */
        chip->select_chip(mtd, -1);
        nand_release_device(mtd);

        /* Do call back function */
        if (!ret)
                mtd_erase_callback(instr);

        /* Return more or less happy */
        return ret;
}

/**
 * nand_sync - [MTD Interface] sync
 * @mtd: MTD device structure
 *
 * Sync is actually a wait for chip ready function.
 */
static void nand_sync(struct mtd_info *mtd)
{
        pr_debug("%s: called\n", __func__);

        /* Grab the lock and see if the device is available */
        nand_get_device(mtd, FL_SYNCING);
        /* Release it and go back */
        nand_release_device(mtd);
}

/**
 * nand_block_isbad - [MTD Interface] Check if block at offset is bad
 * @mtd: MTD device structure
 * @offs: offset relative to mtd start
 */
static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int chipnr = (int)(offs >> chip->chip_shift);
        int ret;

        /* Select the NAND device */
        nand_get_device(mtd, FL_READING);
        chip->select_chip(mtd, chipnr);

        ret = nand_block_checkbad(mtd, offs, 0);

        chip->select_chip(mtd, -1);
        nand_release_device(mtd);

        return ret;
}

/**
 * nand_block_markbad - [MTD Interface] Mark block at the given offset as bad
 * @mtd: MTD device structure
 * @ofs: offset relative to mtd start
 */
static int nand_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
        int ret;

        ret = nand_block_isbad(mtd, ofs);
        if (ret) {
                /* If it was bad already, return success and do nothing */
                if (ret > 0)
                        return 0;
                return ret;
        }

        return nand_block_markbad_lowlevel(mtd, ofs);
}

/**
 * nand_max_bad_blocks - [MTD Interface] Max number of bad blocks for an mtd
 * @mtd: MTD device structure
 * @ofs: offset relative to mtd start
 * @len: length of mtd
 */
static int nand_max_bad_blocks(struct mtd_info *mtd, loff_t ofs, size_t len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        u32 part_start_block;
        u32 part_end_block;
        u32 part_start_die;
        u32 part_end_die;

        /*
         * max_bb_per_die and blocks_per_die used to determine
         * the maximum bad block count.
         */
        if (!chip->max_bb_per_die || !chip->blocks_per_die)
                return -ENOTSUPP;

        /* Get the start and end of the partition in erase blocks. */
        part_start_block = mtd_div_by_eb(ofs, mtd);
        part_end_block = mtd_div_by_eb(len, mtd) + part_start_block - 1;

        /* Get the start and end LUNs of the partition. */
        part_start_die = part_start_block / chip->blocks_per_die;
        part_end_die = part_end_block / chip->blocks_per_die;

        /*
         * Look up the bad blocks per unit and multiply by the number of units
         * that the partition spans.
         */
        return chip->max_bb_per_die * (part_end_die - part_start_die + 1);
}

/**
 * nand_onfi_set_features- [REPLACEABLE] set features for ONFI nand
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 */
static int nand_onfi_set_features(struct mtd_info *mtd, struct nand_chip *chip,
                        int addr, uint8_t *subfeature_param)
{
        int status;
        int i;

        if (!chip->onfi_version ||
            !(le16_to_cpu(chip->onfi_params.opt_cmd)
              & ONFI_OPT_CMD_SET_GET_FEATURES))
                return -EINVAL;

        chip->cmdfunc(mtd, NAND_CMD_SET_FEATURES, addr, -1);
        for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
                chip->write_byte(mtd, subfeature_param[i]);

        status = chip->waitfunc(mtd, chip);
        if (status & NAND_STATUS_FAIL)
                return -EIO;
        return 0;
}

/**
 * nand_onfi_get_features- [REPLACEABLE] get features for ONFI nand
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 */
static int nand_onfi_get_features(struct mtd_info *mtd, struct nand_chip *chip,
                        int addr, uint8_t *subfeature_param)
{
        int i;

        if (!chip->onfi_version ||
            !(le16_to_cpu(chip->onfi_params.opt_cmd)
              & ONFI_OPT_CMD_SET_GET_FEATURES))
                return -EINVAL;

        chip->cmdfunc(mtd, NAND_CMD_GET_FEATURES, addr, -1);
        for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
                *subfeature_param++ = chip->read_byte(mtd);
        return 0;
}

/**
 * nand_onfi_get_set_features_notsupp - set/get features stub returning
 *                                      -ENOTSUPP
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 *
 * Should be used by NAND controller drivers that do not support the SET/GET
 * FEATURES operations.
 */
int nand_onfi_get_set_features_notsupp(struct mtd_info *mtd,
                                       struct nand_chip *chip, int addr,
                                       u8 *subfeature_param)
{
        return -ENOTSUPP;
}
EXPORT_SYMBOL(nand_onfi_get_set_features_notsupp);

/**
 * nand_suspend - [MTD Interface] Suspend the NAND flash
 * @mtd: MTD device structure
 */
static int nand_suspend(struct mtd_info *mtd)
{
        return nand_get_device(mtd, FL_PM_SUSPENDED);
}

/**
 * nand_resume - [MTD Interface] Resume the NAND flash
 * @mtd: MTD device structure
 */
static void nand_resume(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        if (chip->state == FL_PM_SUSPENDED)
                nand_release_device(mtd);
        else
                pr_err("%s called for a chip which is not in suspended state\n",
                        __func__);
}

/**
 * nand_shutdown - [MTD Interface] Finish the current NAND operation and
 *                 prevent further operations
 * @mtd: MTD device structure
 */
static void nand_shutdown(struct mtd_info *mtd)
{
        nand_get_device(mtd, FL_PM_SUSPENDED);
}

/* Set default functions */
static void nand_set_defaults(struct nand_chip *chip)
{
        unsigned int busw = chip->options & NAND_BUSWIDTH_16;

        /* check for proper chip_delay setup, set 20us if not */
        if (!chip->chip_delay)
                chip->chip_delay = 20;

        /* check, if a user supplied command function given */
        if (chip->cmdfunc == NULL)
                chip->cmdfunc = nand_command;

        /* check, if a user supplied wait function given */
        if (chip->waitfunc == NULL)
                chip->waitfunc = nand_wait;

        if (!chip->select_chip)
                chip->select_chip = nand_select_chip;

        /* set for ONFI nand */
        if (!chip->onfi_set_features)
                chip->onfi_set_features = nand_onfi_set_features;
        if (!chip->onfi_get_features)
                chip->onfi_get_features = nand_onfi_get_features;

        /* If called twice, pointers that depend on busw may need to be reset */
        if (!chip->read_byte || chip->read_byte == nand_read_byte)
                chip->read_byte = busw ? nand_read_byte16 : nand_read_byte;
        if (!chip->read_word)
                chip->read_word = nand_read_word;
        if (!chip->block_bad)
                chip->block_bad = nand_block_bad;
        if (!chip->block_markbad)
                chip->block_markbad = nand_default_block_markbad;
        if (!chip->write_buf || chip->write_buf == nand_write_buf)
                chip->write_buf = busw ? nand_write_buf16 : nand_write_buf;
        if (!chip->write_byte || chip->write_byte == nand_write_byte)
                chip->write_byte = busw ? nand_write_byte16 : nand_write_byte;
        if (!chip->read_buf || chip->read_buf == nand_read_buf)
                chip->read_buf = busw ? nand_read_buf16 : nand_read_buf;
        if (!chip->scan_bbt)
                chip->scan_bbt = nand_default_bbt;

        if (!chip->controller) {
                chip->controller = &chip->hwcontrol;
                nand_hw_control_init(chip->controller);
        }

        if (!chip->buf_align)
                chip->buf_align = 1;
}

/* Sanitize ONFI strings so we can safely print them */
static void sanitize_string(uint8_t *s, size_t len)
{
        ssize_t i;

        /* Null terminate */
        s[len - 1] = 0;

        /* Remove non printable chars */
        for (i = 0; i < len - 1; i++) {
                if (s[i] < ' ' || s[i] > 127)
                        s[i] = '?';
        }

        /* Remove trailing spaces */
        strim(s);
}

static u16 onfi_crc16(u16 crc, u8 const *p, size_t len)
{
        int i;
        while (len--) {
                crc ^= *p++ << 8;
                for (i = 0; i < 8; i++)
                        crc = (crc << 1) ^ ((crc & 0x8000) ? 0x8005 : 0);
        }

        return crc;
}

/* Parse the Extended Parameter Page. */
static int nand_flash_detect_ext_param_page(struct nand_chip *chip,
                                            struct nand_onfi_params *p)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct onfi_ext_param_page *ep;
        struct onfi_ext_section *s;
        struct onfi_ext_ecc_info *ecc;
        uint8_t *cursor;
        int ret = -EINVAL;
        int len;
        int i;

        len = le16_to_cpu(p->ext_param_page_length) * 16;
        ep = kmalloc(len, GFP_KERNEL);
        if (!ep)
                return -ENOMEM;

        /* Send our own NAND_CMD_PARAM. */
        chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);

        /* Use the Change Read Column command to skip the ONFI param pages. */
        chip->cmdfunc(mtd, NAND_CMD_RNDOUT,
                        sizeof(*p) * p->num_of_param_pages , -1);

        /* Read out the Extended Parameter Page. */
        chip->read_buf(mtd, (uint8_t *)ep, len);
        if ((onfi_crc16(ONFI_CRC_BASE, ((uint8_t *)ep) + 2, len - 2)
                != le16_to_cpu(ep->crc))) {
                pr_debug("fail in the CRC.\n");
                goto ext_out;
        }

        /*
         * Check the signature.
         * Do not strictly follow the ONFI spec, maybe changed in future.
         */
        if (strncmp(ep->sig, "EPPS", 4)) {
                pr_debug("The signature is invalid.\n");
                goto ext_out;
        }

        /* find the ECC section. */
        cursor = (uint8_t *)(ep + 1);
        for (i = 0; i < ONFI_EXT_SECTION_MAX; i++) {
                s = ep->sections + i;
                if (s->type == ONFI_SECTION_TYPE_2)
                        break;
                cursor += s->length * 16;
        }
        if (i == ONFI_EXT_SECTION_MAX) {
                pr_debug("We can not find the ECC section.\n");
                goto ext_out;
        }

        /* get the info we want. */
        ecc = (struct onfi_ext_ecc_info *)cursor;

        if (!ecc->codeword_size) {
                pr_debug("Invalid codeword size\n");
                goto ext_out;
        }

        chip->ecc_strength_ds = ecc->ecc_bits;
        chip->ecc_step_ds = 1 << ecc->codeword_size;
        ret = 0;

ext_out:
        kfree(ep);
        return ret;
}

/*
 * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
 */
static int nand_flash_detect_onfi(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct nand_onfi_params *p = &chip->onfi_params;
        int i, j;
        int val;

        /* Try ONFI for unknown chip or LP */
        chip->cmdfunc(mtd, NAND_CMD_READID, 0x20, -1);
        if (chip->read_byte(mtd) != 'O' || chip->read_byte(mtd) != 'N' ||
                chip->read_byte(mtd) != 'F' || chip->read_byte(mtd) != 'I')
                return 0;

        chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
        for (i = 0; i < 3; i++) {
                for (j = 0; j < sizeof(*p); j++)
                        ((uint8_t *)p)[j] = chip->read_byte(mtd);
                if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) ==
                                le16_to_cpu(p->crc)) {
                        break;
                }
        }

        if (i == 3) {
                pr_err("Could not find valid ONFI parameter page; aborting\n");
                return 0;
        }

        /* Check version */
        val = le16_to_cpu(p->revision);
        if (val & (1 << 5))
                chip->onfi_version = 23;
        else if (val & (1 << 4))
                chip->onfi_version = 22;
        else if (val & (1 << 3))
                chip->onfi_version = 21;
        else if (val & (1 << 2))
                chip->onfi_version = 20;
        else if (val & (1 << 1))
                chip->onfi_version = 10;

        if (!chip->onfi_version) {
                pr_info("unsupported ONFI version: %d\n", val);
                return 0;
        }

        sanitize_string(p->manufacturer, sizeof(p->manufacturer));
        sanitize_string(p->model, sizeof(p->model));
        if (!mtd->name)
                mtd->name = p->model;

        mtd->writesize = le32_to_cpu(p->byte_per_page);

        /*
         * pages_per_block and blocks_per_lun may not be a power-of-2 size
         * (don't ask me who thought of this...). MTD assumes that these
         * dimensions will be power-of-2, so just truncate the remaining area.
         */
        mtd->erasesize = 1 << (fls(le32_to_cpu(p->pages_per_block)) - 1);
        mtd->erasesize *= mtd->writesize;

        mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);

        /* See erasesize comment */
        chip->chipsize = 1 << (fls(le32_to_cpu(p->blocks_per_lun)) - 1);
        chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
        chip->bits_per_cell = p->bits_per_cell;

        chip->max_bb_per_die = le16_to_cpu(p->bb_per_lun);
        chip->blocks_per_die = le32_to_cpu(p->blocks_per_lun);

        if (onfi_feature(chip) & ONFI_FEATURE_16_BIT_BUS)
                chip->options |= NAND_BUSWIDTH_16;

        if (p->ecc_bits != 0xff) {
                chip->ecc_strength_ds = p->ecc_bits;
                chip->ecc_step_ds = 512;
        } else if (chip->onfi_version >= 21 &&
                (onfi_feature(chip) & ONFI_FEATURE_EXT_PARAM_PAGE)) {

                /*
                 * The nand_flash_detect_ext_param_page() uses the
                 * Change Read Column command which maybe not supported
                 * by the chip->cmdfunc. So try to update the chip->cmdfunc
                 * now. We do not replace user supplied command function.
                 */
                if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
                        chip->cmdfunc = nand_command_lp;

                /* The Extended Parameter Page is supported since ONFI 2.1. */
                if (nand_flash_detect_ext_param_page(chip, p))
                        pr_warn("Failed to detect ONFI extended param page\n");
        } else {
                pr_warn("Could not retrieve ONFI ECC requirements\n");
        }

        return 1;
}

/*
 * Check if the NAND chip is JEDEC compliant, returns 1 if it is, 0 otherwise.
 */
static int nand_flash_detect_jedec(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct nand_jedec_params *p = &chip->jedec_params;
        struct jedec_ecc_info *ecc;
        int val;
        int i, j;

        /* Try JEDEC for unknown chip or LP */
        chip->cmdfunc(mtd, NAND_CMD_READID, 0x40, -1);
        if (chip->read_byte(mtd) != 'J' || chip->read_byte(mtd) != 'E' ||
                chip->read_byte(mtd) != 'D' || chip->read_byte(mtd) != 'E' ||
                chip->read_byte(mtd) != 'C')
                return 0;

        chip->cmdfunc(mtd, NAND_CMD_PARAM, 0x40, -1);
        for (i = 0; i < 3; i++) {
                for (j = 0; j < sizeof(*p); j++)
                        ((uint8_t *)p)[j] = chip->read_byte(mtd);

                if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 510) ==
                                le16_to_cpu(p->crc))
                        break;
        }

        if (i == 3) {
                pr_err("Could not find valid JEDEC parameter page; aborting\n");
                return 0;
        }

        /* Check version */
        val = le16_to_cpu(p->revision);
        if (val & (1 << 2))
                chip->jedec_version = 10;
        else if (val & (1 << 1))
                chip->jedec_version = 1; /* vendor specific version */

        if (!chip->jedec_version) {
                pr_info("unsupported JEDEC version: %d\n", val);
                return 0;
        }

        sanitize_string(p->manufacturer, sizeof(p->manufacturer));
        sanitize_string(p->model, sizeof(p->model));
        if (!mtd->name)
                mtd->name = p->model;

        mtd->writesize = le32_to_cpu(p->byte_per_page);

        /* Please reference to the comment for nand_flash_detect_onfi. */
        mtd->erasesize = 1 << (fls(le32_to_cpu(p->pages_per_block)) - 1);
        mtd->erasesize *= mtd->writesize;

        mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);

        /* Please reference to the comment for nand_flash_detect_onfi. */
        chip->chipsize = 1 << (fls(le32_to_cpu(p->blocks_per_lun)) - 1);
        chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
        chip->bits_per_cell = p->bits_per_cell;

        if (jedec_feature(chip) & JEDEC_FEATURE_16_BIT_BUS)
                chip->options |= NAND_BUSWIDTH_16;

        /* ECC info */
        ecc = &p->ecc_info[0];

        if (ecc->codeword_size >= 9) {
                chip->ecc_strength_ds = ecc->ecc_bits;
                chip->ecc_step_ds = 1 << ecc->codeword_size;
        } else {
                pr_warn("Invalid codeword size\n");
        }

        return 1;
}

/*
 * nand_id_has_period - Check if an ID string has a given wraparound period
 * @id_data: the ID string
 * @arrlen: the length of the @id_data array
 * @period: the period of repitition
 *
 * Check if an ID string is repeated within a given sequence of bytes at
 * specific repetition interval period (e.g., {0x20,0x01,0x7F,0x20} has a
 * period of 3). This is a helper function for nand_id_len(). Returns non-zero
 * if the repetition has a period of @period; otherwise, returns zero.
 */
static int nand_id_has_period(u8 *id_data, int arrlen, int period)
{
        int i, j;
        for (i = 0; i < period; i++)
                for (j = i + period; j < arrlen; j += period)
                        if (id_data[i] != id_data[j])
                                return 0;
        return 1;
}

/*
 * nand_id_len - Get the length of an ID string returned by CMD_READID
 * @id_data: the ID string
 * @arrlen: the length of the @id_data array

 * Returns the length of the ID string, according to known wraparound/trailing
 * zero patterns. If no pattern exists, returns the length of the array.
 */
static int nand_id_len(u8 *id_data, int arrlen)
{
        int last_nonzero, period;

        /* Find last non-zero byte */
        for (last_nonzero = arrlen - 1; last_nonzero >= 0; last_nonzero--)
                if (id_data[last_nonzero])
                        break;

        /* All zeros */
        if (last_nonzero < 0)
                return 0;

        /* Calculate wraparound period */
        for (period = 1; period < arrlen; period++)
                if (nand_id_has_period(id_data, arrlen, period))
                        break;

        /* There's a repeated pattern */
        if (period < arrlen)
                return period;

        /* There are trailing zeros */
        if (last_nonzero < arrlen - 1)
                return last_nonzero + 1;

        /* No pattern detected */
        return arrlen;
}

/* Extract the bits of per cell from the 3rd byte of the extended ID */
static int nand_get_bits_per_cell(u8 cellinfo)
{
        int bits;

        bits = cellinfo & NAND_CI_CELLTYPE_MSK;
        bits >>= NAND_CI_CELLTYPE_SHIFT;
        return bits + 1;
}

/*
 * Many new NAND share similar device ID codes, which represent the size of the
 * chip. The rest of the parameters must be decoded according to generic or
 * manufacturer-specific "extended ID" decoding patterns.
 */
void nand_decode_ext_id(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        int extid;
        u8 *id_data = chip->id.data;
        /* The 3rd id byte holds MLC / multichip data */
        chip->bits_per_cell = nand_get_bits_per_cell(id_data[2]);
        /* The 4th id byte is the important one */
        extid = id_data[3];

        /* Calc pagesize */
        mtd->writesize = 1024 << (extid & 0x03);
        extid >>= 2;
        /* Calc oobsize */
        mtd->oobsize = (8 << (extid & 0x01)) * (mtd->writesize >> 9);
        extid >>= 2;
        /* Calc blocksize. Blocksize is multiples of 64KiB */
        mtd->erasesize = (64 * 1024) << (extid & 0x03);
        extid >>= 2;
        /* Get buswidth information */
        if (extid & 0x1)
                chip->options |= NAND_BUSWIDTH_16;
}
EXPORT_SYMBOL_GPL(nand_decode_ext_id);

/*
 * Old devices have chip data hardcoded in the device ID table. nand_decode_id
 * decodes a matching ID table entry and assigns the MTD size parameters for
 * the chip.
 */
static void nand_decode_id(struct nand_chip *chip, struct nand_flash_dev *type)
{
        struct mtd_info *mtd = nand_to_mtd(chip);

        mtd->erasesize = type->erasesize;
        mtd->writesize = type->pagesize;
        mtd->oobsize = mtd->writesize / 32;

        /* All legacy ID NAND are small-page, SLC */
        chip->bits_per_cell = 1;
}

/*
 * Set the bad block marker/indicator (BBM/BBI) patterns according to some
 * heuristic patterns using various detected parameters (e.g., manufacturer,
 * page size, cell-type information).
 */
static void nand_decode_bbm_options(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);

        /* Set the bad block position */
        if (mtd->writesize > 512 || (chip->options & NAND_BUSWIDTH_16))
                chip->badblockpos = NAND_LARGE_BADBLOCK_POS;
        else
                chip->badblockpos = NAND_SMALL_BADBLOCK_POS;
}

static inline bool is_full_id_nand(struct nand_flash_dev *type)
{
        return type->id_len;
}

static bool find_full_id_nand(struct nand_chip *chip,
                              struct nand_flash_dev *type)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        u8 *id_data = chip->id.data;

        if (!strncmp(type->id, id_data, type->id_len)) {
                mtd->writesize = type->pagesize;
                mtd->erasesize = type->erasesize;
                mtd->oobsize = type->oobsize;

                chip->bits_per_cell = nand_get_bits_per_cell(id_data[2]);
                chip->chipsize = (uint64_t)type->chipsize << 20;
                chip->options |= type->options;
                chip->ecc_strength_ds = NAND_ECC_STRENGTH(type);
                chip->ecc_step_ds = NAND_ECC_STEP(type);
                chip->onfi_timing_mode_default =
                                        type->onfi_timing_mode_default;

                if (!mtd->name)
                        mtd->name = type->name;

                return true;
        }
        return false;
}

/*
 * Manufacturer detection. Only used when the NAND is not ONFI or JEDEC
 * compliant and does not have a full-id or legacy-id entry in the nand_ids
 * table.
 */
static void nand_manufacturer_detect(struct nand_chip *chip)
{
        /*
         * Try manufacturer detection if available and use
         * nand_decode_ext_id() otherwise.
         */
        if (chip->manufacturer.desc && chip->manufacturer.desc->ops &&
            chip->manufacturer.desc->ops->detect) {
                /* The 3rd id byte holds MLC / multichip data */
                chip->bits_per_cell = nand_get_bits_per_cell(chip->id.data[2]);
                chip->manufacturer.desc->ops->detect(chip);
        } else {
                nand_decode_ext_id(chip);
        }
}

/*
 * Manufacturer initialization. This function is called for all NANDs including
 * ONFI and JEDEC compliant ones.
 * Manufacturer drivers should put all their specific initialization code in
 * their ->init() hook.
 */
static int nand_manufacturer_init(struct nand_chip *chip)
{
        if (!chip->manufacturer.desc || !chip->manufacturer.desc->ops ||
            !chip->manufacturer.desc->ops->init)
                return 0;

        return chip->manufacturer.desc->ops->init(chip);
}

/*
 * Manufacturer cleanup. This function is called for all NANDs including
 * ONFI and JEDEC compliant ones.
 * Manufacturer drivers should put all their specific cleanup code in their
 * ->cleanup() hook.
 */
static void nand_manufacturer_cleanup(struct nand_chip *chip)
{
        /* Release manufacturer private data */
        if (chip->manufacturer.desc && chip->manufacturer.desc->ops &&
            chip->manufacturer.desc->ops->cleanup)
                chip->manufacturer.desc->ops->cleanup(chip);
}

/*
 * Get the flash and manufacturer id and lookup if the type is supported.
 */
static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
{
        const struct nand_manufacturer *manufacturer;
        struct mtd_info *mtd = nand_to_mtd(chip);
        int busw;
        int i;
        u8 *id_data = chip->id.data;
        u8 maf_id, dev_id;

        /*
         * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx)
         * after power-up.
         */
        nand_reset(chip, 0);

        /* Select the device */
        chip->select_chip(mtd, 0);

        /* Send the command for reading device ID */
        chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);

        /* Read manufacturer and device IDs */
        maf_id = chip->read_byte(mtd);
        dev_id = chip->read_byte(mtd);

        /*
         * Try again to make sure, as some systems the bus-hold or other
         * interface concerns can cause random data which looks like a
         * possibly credible NAND flash to appear. If the two results do
         * not match, ignore the device completely.
         */

        chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);

        /* Read entire ID string */
        for (i = 0; i < ARRAY_SIZE(chip->id.data); i++)
                id_data[i] = chip->read_byte(mtd);

        if (id_data[0] != maf_id || id_data[1] != dev_id) {
                pr_info("second ID read did not match %02x,%02x against %02x,%02x\n",
                        maf_id, dev_id, id_data[0], id_data[1]);
                return -ENODEV;
        }

        chip->id.len = nand_id_len(id_data, ARRAY_SIZE(chip->id.data));

        /* Try to identify manufacturer */
        manufacturer = nand_get_manufacturer(maf_id);
        chip->manufacturer.desc = manufacturer;

        if (!type)
                type = nand_flash_ids;

        /*
         * Save the NAND_BUSWIDTH_16 flag before letting auto-detection logic
         * override it.
         * This is required to make sure initial NAND bus width set by the
         * NAND controller driver is coherent with the real NAND bus width
         * (extracted by auto-detection code).
         */
        busw = chip->options & NAND_BUSWIDTH_16;

        /*
         * The flag is only set (never cleared), reset it to its default value
         * before starting auto-detection.
         */
        chip->options &= ~NAND_BUSWIDTH_16;

        for (; type->name != NULL; type++) {
                if (is_full_id_nand(type)) {
                        if (find_full_id_nand(chip, type))
                                goto ident_done;
                } else if (dev_id == type->dev_id) {
                        break;
                }
        }

        chip->onfi_version = 0;
        if (!type->name || !type->pagesize) {
                /* Check if the chip is ONFI compliant */
                if (nand_flash_detect_onfi(chip))
                        goto ident_done;

                /* Check if the chip is JEDEC compliant */
                if (nand_flash_detect_jedec(chip))
                        goto ident_done;
        }

        if (!type->name)
                return -ENODEV;

        if (!mtd->name)
                mtd->name = type->name;

        chip->chipsize = (uint64_t)type->chipsize << 20;

        if (!type->pagesize)
                nand_manufacturer_detect(chip);
        else
                nand_decode_id(chip, type);

        /* Get chip options */
        chip->options |= type->options;

ident_done:

        if (chip->options & NAND_BUSWIDTH_AUTO) {
                WARN_ON(busw & NAND_BUSWIDTH_16);
                nand_set_defaults(chip);
        } else if (busw != (chip->options & NAND_BUSWIDTH_16)) {
                /*
                 * Check, if buswidth is correct. Hardware drivers should set
                 * chip correct!
                 */
                pr_info("device found, Manufacturer ID: 0x%02x, Chip ID: 0x%02x\n",
                        maf_id, dev_id);
                pr_info("%s %s\n", nand_manufacturer_name(manufacturer),
                        mtd->name);
                pr_warn("bus width %d instead of %d bits\n", busw ? 16 : 8,
                        (chip->options & NAND_BUSWIDTH_16) ? 16 : 8);
                return -EINVAL;
        }

        nand_decode_bbm_options(chip);

        /* Calculate the address shift from the page size */
        chip->page_shift = ffs(mtd->writesize) - 1;
        /* Convert chipsize to number of pages per chip -1 */
        chip->pagemask = (chip->chipsize >> chip->page_shift) - 1;

        chip->bbt_erase_shift = chip->phys_erase_shift =
                ffs(mtd->erasesize) - 1;
        if (chip->chipsize & 0xffffffff)
                chip->chip_shift = ffs((unsigned)chip->chipsize) - 1;
        else {
                chip->chip_shift = ffs((unsigned)(chip->chipsize >> 32));
                chip->chip_shift += 32 - 1;
        }

        chip->badblockbits = 8;
        chip->erase = single_erase;

        /* Do not replace user supplied command function! */
        if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
                chip->cmdfunc = nand_command_lp;

        pr_info("device found, Manufacturer ID: 0x%02x, Chip ID: 0x%02x\n",
                maf_id, dev_id);

        if (chip->onfi_version)
                pr_info("%s %s\n", nand_manufacturer_name(manufacturer),
                        chip->onfi_params.model);
        else if (chip->jedec_version)
                pr_info("%s %s\n", nand_manufacturer_name(manufacturer),
                        chip->jedec_params.model);
        else
                pr_info("%s %s\n", nand_manufacturer_name(manufacturer),
                        type->name);

        pr_info("%d MiB, %s, erase size: %d KiB, page size: %d, OOB size: %d\n",
                (int)(chip->chipsize >> 20), nand_is_slc(chip) ? "SLC" : "MLC",
                mtd->erasesize >> 10, mtd->writesize, mtd->oobsize);
        return 0;
}

static const char * const nand_ecc_modes[] = {
        [NAND_ECC_NONE]         = "none",
        [NAND_ECC_SOFT]         = "soft",
        [NAND_ECC_HW]           = "hw",
        [NAND_ECC_HW_SYNDROME]  = "hw_syndrome",
        [NAND_ECC_HW_OOB_FIRST] = "hw_oob_first",
        [NAND_ECC_ON_DIE]       = "on-die",
};

static int of_get_nand_ecc_mode(struct device_node *np)
{
        const char *pm;
        int err, i;

        err = of_property_read_string(np, "nand-ecc-mode", &pm);
        if (err < 0)
                return err;

        for (i = 0; i < ARRAY_SIZE(nand_ecc_modes); i++)
                if (!strcasecmp(pm, nand_ecc_modes[i]))
                        return i;

        /*
         * For backward compatibility we support few obsoleted values that don't
         * have their mappings into nand_ecc_modes_t anymore (they were merged
         * with other enums).
         */
        if (!strcasecmp(pm, "soft_bch"))
                return NAND_ECC_SOFT;

        return -ENODEV;
}

static const char * const nand_ecc_algos[] = {
        [NAND_ECC_HAMMING]      = "hamming",
        [NAND_ECC_BCH]          = "bch",
};

static int of_get_nand_ecc_algo(struct device_node *np)
{
        const char *pm;
        int err, i;

        err = of_property_read_string(np, "nand-ecc-algo", &pm);
        if (!err) {
                for (i = NAND_ECC_HAMMING; i < ARRAY_SIZE(nand_ecc_algos); i++)
                        if (!strcasecmp(pm, nand_ecc_algos[i]))
                                return i;
                return -ENODEV;
        }

        /*
         * For backward compatibility we also read "nand-ecc-mode" checking
         * for some obsoleted values that were specifying ECC algorithm.
         */
        err = of_property_read_string(np, "nand-ecc-mode", &pm);
        if (err < 0)
                return err;

        if (!strcasecmp(pm, "soft"))
                return NAND_ECC_HAMMING;
        else if (!strcasecmp(pm, "soft_bch"))
                return NAND_ECC_BCH;

        return -ENODEV;
}

static int of_get_nand_ecc_step_size(struct device_node *np)
{
        int ret;
        u32 val;

        ret = of_property_read_u32(np, "nand-ecc-step-size", &val);
        return ret ? ret : val;
}

static int of_get_nand_ecc_strength(struct device_node *np)
{
        int ret;
        u32 val;

        ret = of_property_read_u32(np, "nand-ecc-strength", &val);
        return ret ? ret : val;
}

static int of_get_nand_bus_width(struct device_node *np)
{
        u32 val;

        if (of_property_read_u32(np, "nand-bus-width", &val))
                return 8;

        switch (val) {
        case 8:
        case 16:
                return val;
        default:
                return -EIO;
        }
}

static bool of_get_nand_on_flash_bbt(struct device_node *np)
{
        return of_property_read_bool(np, "nand-on-flash-bbt");
}

static int nand_dt_init(struct nand_chip *chip)
{
        struct device_node *dn = nand_get_flash_node(chip);
        int ecc_mode, ecc_algo, ecc_strength, ecc_step;

        if (!dn)
                return 0;

        if (of_get_nand_bus_width(dn) == 16)
                chip->options |= NAND_BUSWIDTH_16;

        if (of_get_nand_on_flash_bbt(dn))
                chip->bbt_options |= NAND_BBT_USE_FLASH;

        ecc_mode = of_get_nand_ecc_mode(dn);
        ecc_algo = of_get_nand_ecc_algo(dn);
        ecc_strength = of_get_nand_ecc_strength(dn);
        ecc_step = of_get_nand_ecc_step_size(dn);

        if (ecc_mode >= 0)
                chip->ecc.mode = ecc_mode;

        if (ecc_algo >= 0)
                chip->ecc.algo = ecc_algo;

        if (ecc_strength >= 0)
                chip->ecc.strength = ecc_strength;

        if (ecc_step > 0)
                chip->ecc.size = ecc_step;

        if (of_property_read_bool(dn, "nand-ecc-maximize"))
                chip->ecc.options |= NAND_ECC_MAXIMIZE;

        return 0;
}

/**
 * nand_scan_ident - [NAND Interface] Scan for the NAND device
 * @mtd: MTD device structure
 * @maxchips: number of chips to scan for
 * @table: alternative NAND ID table
 *
 * This is the first phase of the normal nand_scan() function. It reads the
 * flash ID and sets up MTD fields accordingly.
 *
 */
int nand_scan_ident(struct mtd_info *mtd, int maxchips,
                    struct nand_flash_dev *table)
{
        int i, nand_maf_id, nand_dev_id;
        struct nand_chip *chip = mtd_to_nand(mtd);
        int ret;

        ret = nand_dt_init(chip);
        if (ret)
                return ret;

        if (!mtd->name && mtd->dev.parent)
                mtd->name = dev_name(mtd->dev.parent);

        if ((!chip->cmdfunc || !chip->select_chip) && !chip->cmd_ctrl) {
                /*
                 * Default functions assigned for chip_select() and
                 * cmdfunc() both expect cmd_ctrl() to be populated,
                 * so we need to check that that's the case
                 */
                pr_err("chip.cmd_ctrl() callback is not provided");
                return -EINVAL;
        }
        /* Set the default functions */
        nand_set_defaults(chip);

        /* Read the flash type */
        ret = nand_detect(chip, table);
        if (ret) {
                if (!(chip->options & NAND_SCAN_SILENT_NODEV))
                        pr_warn("No NAND device found\n");
                chip->select_chip(mtd, -1);
                return ret;
        }

        nand_maf_id = chip->id.data[0];
        nand_dev_id = chip->id.data[1];

        chip->select_chip(mtd, -1);

        /* Check for a chip array */
        for (i = 1; i < maxchips; i++) {
                /* See comment in nand_get_flash_type for reset */
                nand_reset(chip, i);

                chip->select_chip(mtd, i);
                /* Send the command for reading device ID */
                chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
                /* Read manufacturer and device IDs */
                if (nand_maf_id != chip->read_byte(mtd) ||
                    nand_dev_id != chip->read_byte(mtd)) {
                        chip->select_chip(mtd, -1);
                        break;
                }
                chip->select_chip(mtd, -1);
        }
        if (i > 1)
                pr_info("%d chips detected\n", i);

        /* Store the number of chips and calc total size for mtd */
        chip->numchips = i;
        mtd->size = i * chip->chipsize;

        return 0;
}
EXPORT_SYMBOL(nand_scan_ident);

static int nand_set_ecc_soft_ops(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;

        if (WARN_ON(ecc->mode != NAND_ECC_SOFT))
                return -EINVAL;

        switch (ecc->algo) {
        case NAND_ECC_HAMMING:
                ecc->calculate = nand_calculate_ecc;
                ecc->correct = nand_correct_data;
                ecc->read_page = nand_read_page_swecc;
                ecc->read_subpage = nand_read_subpage;
                ecc->write_page = nand_write_page_swecc;
                ecc->read_page_raw = nand_read_page_raw;
                ecc->write_page_raw = nand_write_page_raw;
                ecc->read_oob = nand_read_oob_std;
                ecc->write_oob = nand_write_oob_std;
                if (!ecc->size)
                        ecc->size = 256;
                ecc->bytes = 3;
                ecc->strength = 1;
                return 0;
        case NAND_ECC_BCH:
                if (!mtd_nand_has_bch()) {
                        WARN(1, "CONFIG_MTD_NAND_ECC_BCH not enabled\n");
                        return -EINVAL;
                }
                ecc->calculate = nand_bch_calculate_ecc;
                ecc->correct = nand_bch_correct_data;
                ecc->read_page = nand_read_page_swecc;
                ecc->read_subpage = nand_read_subpage;
                ecc->write_page = nand_write_page_swecc;
                ecc->read_page_raw = nand_read_page_raw;
                ecc->write_page_raw = nand_write_page_raw;
                ecc->read_oob = nand_read_oob_std;
                ecc->write_oob = nand_write_oob_std;

                /*
                * Board driver should supply ecc.size and ecc.strength
                * values to select how many bits are correctable.
                * Otherwise, default to 4 bits for large page devices.
                */
                if (!ecc->size && (mtd->oobsize >= 64)) {
                        ecc->size = 512;
                        ecc->strength = 4;
                }

                /*
                 * if no ecc placement scheme was provided pickup the default
                 * large page one.
                 */
                if (!mtd->ooblayout) {
                        /* handle large page devices only */
                        if (mtd->oobsize < 64) {
                                WARN(1, "OOB layout is required when using software BCH on small pages\n");
                                return -EINVAL;
                        }

                        mtd_set_ooblayout(mtd, &nand_ooblayout_lp_ops);

                }

                /*
                 * We can only maximize ECC config when the default layout is
                 * used, otherwise we don't know how many bytes can really be
                 * used.
                 */
                if (mtd->ooblayout == &nand_ooblayout_lp_ops &&
                    ecc->options & NAND_ECC_MAXIMIZE) {
                        int steps, bytes;

                        /* Always prefer 1k blocks over 512bytes ones */
                        ecc->size = 1024;
                        steps = mtd->writesize / ecc->size;

                        /* Reserve 2 bytes for the BBM */
                        bytes = (mtd->oobsize - 2) / steps;
                        ecc->strength = bytes * 8 / fls(8 * ecc->size);
                }

                /* See nand_bch_init() for details. */
                ecc->bytes = 0;
                ecc->priv = nand_bch_init(mtd);
                if (!ecc->priv) {
                        WARN(1, "BCH ECC initialization failed!\n");
                        return -EINVAL;
                }
                return 0;
        default:
                WARN(1, "Unsupported ECC algorithm!\n");
                return -EINVAL;
        }
}

/**
 * nand_check_ecc_caps - check the sanity of preset ECC settings
 * @chip: nand chip info structure
 * @caps: ECC caps info structure
 * @oobavail: OOB size that the ECC engine can use
 *
 * When ECC step size and strength are already set, check if they are supported
 * by the controller and the calculated ECC bytes fit within the chip's OOB.
 * On success, the calculated ECC bytes is set.
 */
int nand_check_ecc_caps(struct nand_chip *chip,
                        const struct nand_ecc_caps *caps, int oobavail)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        const struct nand_ecc_step_info *stepinfo;
        int preset_step = chip->ecc.size;
        int preset_strength = chip->ecc.strength;
        int nsteps, ecc_bytes;
        int i, j;

        if (WARN_ON(oobavail < 0))
                return -EINVAL;

        if (!preset_step || !preset_strength)
                return -ENODATA;

        nsteps = mtd->writesize / preset_step;

        for (i = 0; i < caps->nstepinfos; i++) {
                stepinfo = &caps->stepinfos[i];

                if (stepinfo->stepsize != preset_step)
                        continue;

                for (j = 0; j < stepinfo->nstrengths; j++) {
                        if (stepinfo->strengths[j] != preset_strength)
                                continue;

                        ecc_bytes = caps->calc_ecc_bytes(preset_step,
                                                         preset_strength);
                        if (WARN_ON_ONCE(ecc_bytes < 0))
                                return ecc_bytes;

                        if (ecc_bytes * nsteps > oobavail) {
                                pr_err("ECC (step, strength) = (%d, %d) does not fit in OOB",
                                       preset_step, preset_strength);
                                return -ENOSPC;
                        }

                        chip->ecc.bytes = ecc_bytes;

                        return 0;
                }
        }

        pr_err("ECC (step, strength) = (%d, %d) not supported on this controller",
               preset_step, preset_strength);

        return -ENOTSUPP;
}
EXPORT_SYMBOL_GPL(nand_check_ecc_caps);

/**
 * nand_match_ecc_req - meet the chip's requirement with least ECC bytes
 * @chip: nand chip info structure
 * @caps: ECC engine caps info structure
 * @oobavail: OOB size that the ECC engine can use
 *
 * If a chip's ECC requirement is provided, try to meet it with the least
 * number of ECC bytes (i.e. with the largest number of OOB-free bytes).
 * On success, the chosen ECC settings are set.
 */
int nand_match_ecc_req(struct nand_chip *chip,
                       const struct nand_ecc_caps *caps, int oobavail)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        const struct nand_ecc_step_info *stepinfo;
        int req_step = chip->ecc_step_ds;
        int req_strength = chip->ecc_strength_ds;
        int req_corr, step_size, strength, nsteps, ecc_bytes, ecc_bytes_total;
        int best_step, best_strength, best_ecc_bytes;
        int best_ecc_bytes_total = INT_MAX;
        int i, j;

        if (WARN_ON(oobavail < 0))
                return -EINVAL;

        /* No information provided by the NAND chip */
        if (!req_step || !req_strength)
                return -ENOTSUPP;

        /* number of correctable bits the chip requires in a page */
        req_corr = mtd->writesize / req_step * req_strength;

        for (i = 0; i < caps->nstepinfos; i++) {
                stepinfo = &caps->stepinfos[i];
                step_size = stepinfo->stepsize;

                for (j = 0; j < stepinfo->nstrengths; j++) {
                        strength = stepinfo->strengths[j];

                        /*
                         * If both step size and strength are smaller than the
                         * chip's requirement, it is not easy to compare the
                         * resulted reliability.
                         */
                        if (step_size < req_step && strength < req_strength)
                                continue;

                        if (mtd->writesize % step_size)
                                continue;

                        nsteps = mtd->writesize / step_size;

                        ecc_bytes = caps->calc_ecc_bytes(step_size, strength);
                        if (WARN_ON_ONCE(ecc_bytes < 0))
                                continue;
                        ecc_bytes_total = ecc_bytes * nsteps;

                        if (ecc_bytes_total > oobavail ||
                            strength * nsteps < req_corr)
                                continue;

                        /*
                         * We assume the best is to meet the chip's requrement
                         * with the least number of ECC bytes.
                         */
                        if (ecc_bytes_total < best_ecc_bytes_total) {
                                best_ecc_bytes_total = ecc_bytes_total;
                                best_step = step_size;
                                best_strength = strength;
                                best_ecc_bytes = ecc_bytes;
                        }
                }
        }

        if (best_ecc_bytes_total == INT_MAX)
                return -ENOTSUPP;

        chip->ecc.size = best_step;
        chip->ecc.strength = best_strength;
        chip->ecc.bytes = best_ecc_bytes;

        return 0;
}
EXPORT_SYMBOL_GPL(nand_match_ecc_req);

/**
 * nand_maximize_ecc - choose the max ECC strength available
 * @chip: nand chip info structure
 * @caps: ECC engine caps info structure
 * @oobavail: OOB size that the ECC engine can use
 *
 * Choose the max ECC strength that is supported on the controller, and can fit
 * within the chip's OOB.  On success, the chosen ECC settings are set.
 */
int nand_maximize_ecc(struct nand_chip *chip,
                      const struct nand_ecc_caps *caps, int oobavail)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        const struct nand_ecc_step_info *stepinfo;
        int step_size, strength, nsteps, ecc_bytes, corr;
        int best_corr = 0;
        int best_step = 0;
        int best_strength, best_ecc_bytes;
        int i, j;

        if (WARN_ON(oobavail < 0))
                return -EINVAL;

        for (i = 0; i < caps->nstepinfos; i++) {
                stepinfo = &caps->stepinfos[i];
                step_size = stepinfo->stepsize;

                /* If chip->ecc.size is already set, respect it */
                if (chip->ecc.size && step_size != chip->ecc.size)
                        continue;

                for (j = 0; j < stepinfo->nstrengths; j++) {
                        strength = stepinfo->strengths[j];

                        if (mtd->writesize % step_size)
                                continue;

                        nsteps = mtd->writesize / step_size;

                        ecc_bytes = caps->calc_ecc_bytes(step_size, strength);
                        if (WARN_ON_ONCE(ecc_bytes < 0))
                                continue;

                        if (ecc_bytes * nsteps > oobavail)
                                continue;

                        corr = strength * nsteps;

                        /*
                         * If the number of correctable bits is the same,
                         * bigger step_size has more reliability.
                         */
                        if (corr > best_corr ||
                            (corr == best_corr && step_size > best_step)) {
                                best_corr = corr;
                                best_step = step_size;
                                best_strength = strength;
                                best_ecc_bytes = ecc_bytes;
                        }
                }
        }

        if (!best_corr)
                return -ENOTSUPP;

        chip->ecc.size = best_step;
        chip->ecc.strength = best_strength;
        chip->ecc.bytes = best_ecc_bytes;

        return 0;
}
EXPORT_SYMBOL_GPL(nand_maximize_ecc);

/*
 * Check if the chip configuration meet the datasheet requirements.

 * If our configuration corrects A bits per B bytes and the minimum
 * required correction level is X bits per Y bytes, then we must ensure
 * both of the following are true:
 *
 * (1) A / B >= X / Y
 * (2) A >= X
 *
 * Requirement (1) ensures we can correct for the required bitflip density.
 * Requirement (2) ensures we can correct even when all bitflips are clumped
 * in the same sector.
 */
static bool nand_ecc_strength_good(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;
        int corr, ds_corr;

        if (ecc->size == 0 || chip->ecc_step_ds == 0)
                /* Not enough information */
                return true;

        /*
         * We get the number of corrected bits per page to compare
         * the correction density.
         */
        corr = (mtd->writesize * ecc->strength) / ecc->size;
        ds_corr = (mtd->writesize * chip->ecc_strength_ds) / chip->ecc_step_ds;

        return corr >= ds_corr && ecc->strength >= chip->ecc_strength_ds;
}

static bool invalid_ecc_page_accessors(struct nand_chip *chip)
{
        struct nand_ecc_ctrl *ecc = &chip->ecc;

        if (nand_standard_page_accessors(ecc))
                return false;

        /*
         * NAND_ECC_CUSTOM_PAGE_ACCESS flag is set, make sure the NAND
         * controller driver implements all the page accessors because
         * default helpers are not suitable when the core does not
         * send the READ0/PAGEPROG commands.
         */
        return (!ecc->read_page || !ecc->write_page ||
                !ecc->read_page_raw || !ecc->write_page_raw ||
                (NAND_HAS_SUBPAGE_READ(chip) && !ecc->read_subpage) ||
                (NAND_HAS_SUBPAGE_WRITE(chip) && !ecc->write_subpage &&
                 ecc->hwctl && ecc->calculate));
}

/**
 * nand_scan_tail - [NAND Interface] Scan for the NAND device
 * @mtd: MTD device structure
 *
 * This is the second phase of the normal nand_scan() function. It fills out
 * all the uninitialized function pointers with the defaults and scans for a
 * bad block table if appropriate.
 */
int nand_scan_tail(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;
        struct nand_buffers *nbuf = NULL;
        int ret, i;

        /* New bad blocks should be marked in OOB, flash-based BBT, or both */
        if (WARN_ON((chip->bbt_options & NAND_BBT_NO_OOB_BBM) &&
                   !(chip->bbt_options & NAND_BBT_USE_FLASH))) {
                return -EINVAL;
        }

        if (invalid_ecc_page_accessors(chip)) {
                pr_err("Invalid ECC page accessors setup\n");
                return -EINVAL;
        }

        if (!(chip->options & NAND_OWN_BUFFERS)) {
                nbuf = kzalloc(sizeof(*nbuf), GFP_KERNEL);
                if (!nbuf)
                        return -ENOMEM;

                nbuf->ecccalc = kmalloc(mtd->oobsize, GFP_KERNEL);
                if (!nbuf->ecccalc) {
                        ret = -ENOMEM;
                        goto err_free_nbuf;
                }

                nbuf->ecccode = kmalloc(mtd->oobsize, GFP_KERNEL);
                if (!nbuf->ecccode) {
                        ret = -ENOMEM;
                        goto err_free_nbuf;
                }

                nbuf->databuf = kmalloc(mtd->writesize + mtd->oobsize,
                                        GFP_KERNEL);
                if (!nbuf->databuf) {
                        ret = -ENOMEM;
                        goto err_free_nbuf;
                }

                chip->buffers = nbuf;
        } else if (!chip->buffers) {
                return -ENOMEM;
        }

        /*
         * FIXME: some NAND manufacturer drivers expect the first die to be
         * selected when manufacturer->init() is called. They should be fixed
         * to explictly select the relevant die when interacting with the NAND
         * chip.
         */
        chip->select_chip(mtd, 0);
        ret = nand_manufacturer_init(chip);
        chip->select_chip(mtd, -1);
        if (ret)
                goto err_free_nbuf;

        /* Set the internal oob buffer location, just after the page data */
        chip->oob_poi = chip->buffers->databuf + mtd->writesize;

        /*
         * If no default placement scheme is given, select an appropriate one.
         */
        if (!mtd->ooblayout &&
            !(ecc->mode == NAND_ECC_SOFT && ecc->algo == NAND_ECC_BCH)) {
                switch (mtd->oobsize) {
                case 8:
                case 16:
                        mtd_set_ooblayout(mtd, &nand_ooblayout_sp_ops);
                        break;
                case 64:
                case 128:
                        mtd_set_ooblayout(mtd, &nand_ooblayout_lp_hamming_ops);
                        break;
                default:
                        /*
                         * Expose the whole OOB area to users if ECC_NONE
                         * is passed. We could do that for all kind of
                         * ->oobsize, but we must keep the old large/small
                         * page with ECC layout when ->oobsize <= 128 for
                         * compatibility reasons.
                         */
                        if (ecc->mode == NAND_ECC_NONE) {
                                mtd_set_ooblayout(mtd,
                                                &nand_ooblayout_lp_ops);
                                break;
                        }

                        WARN(1, "No oob scheme defined for oobsize %d\n",
                                mtd->oobsize);
                        ret = -EINVAL;
                        goto err_nand_manuf_cleanup;
                }
        }

        /*
         * Check ECC mode, default to software if 3byte/512byte hardware ECC is
         * selected and we have 256 byte pagesize fallback to software ECC
         */

        switch (ecc->mode) {
        case NAND_ECC_HW_OOB_FIRST:
                /* Similar to NAND_ECC_HW, but a separate read_page handle */
                if (!ecc->calculate || !ecc->correct || !ecc->hwctl) {
                        WARN(1, "No ECC functions supplied; hardware ECC not possible\n");
                        ret = -EINVAL;
                        goto err_nand_manuf_cleanup;
                }
                if (!ecc->read_page)
                        ecc->read_page = nand_read_page_hwecc_oob_first;

        case NAND_ECC_HW:
                /* Use standard hwecc read page function? */
                if (!ecc->read_page)
                        ecc->read_page = nand_read_page_hwecc;
                if (!ecc->write_page)
                        ecc->write_page = nand_write_page_hwecc;
                if (!ecc->read_page_raw)
                        ecc->read_page_raw = nand_read_page_raw;
                if (!ecc->write_page_raw)
                        ecc->write_page_raw = nand_write_page_raw;
                if (!ecc->read_oob)
                        ecc->read_oob = nand_read_oob_std;
                if (!ecc->write_oob)
                        ecc->write_oob = nand_write_oob_std;
                if (!ecc->read_subpage)
                        ecc->read_subpage = nand_read_subpage;
                if (!ecc->write_subpage && ecc->hwctl && ecc->calculate)
                        ecc->write_subpage = nand_write_subpage_hwecc;

        case NAND_ECC_HW_SYNDROME:
                if ((!ecc->calculate || !ecc->correct || !ecc->hwctl) &&
                    (!ecc->read_page ||
                     ecc->read_page == nand_read_page_hwecc ||
                     !ecc->write_page ||
                     ecc->write_page == nand_write_page_hwecc)) {
                        WARN(1, "No ECC functions supplied; hardware ECC not possible\n");
                        ret = -EINVAL;
                        goto err_nand_manuf_cleanup;
                }
                /* Use standard syndrome read/write page function? */
                if (!ecc->read_page)
                        ecc->read_page = nand_read_page_syndrome;
                if (!ecc->write_page)
                        ecc->write_page = nand_write_page_syndrome;
                if (!ecc->read_page_raw)
                        ecc->read_page_raw = nand_read_page_raw_syndrome;
                if (!ecc->write_page_raw)
                        ecc->write_page_raw = nand_write_page_raw_syndrome;
                if (!ecc->read_oob)
                        ecc->read_oob = nand_read_oob_syndrome;
                if (!ecc->write_oob)
                        ecc->write_oob = nand_write_oob_syndrome;

                if (mtd->writesize >= ecc->size) {
                        if (!ecc->strength) {
                                WARN(1, "Driver must set ecc.strength when using hardware ECC\n");
                                ret = -EINVAL;
                                goto err_nand_manuf_cleanup;
                        }
                        break;
                }
                pr_warn("%d byte HW ECC not possible on %d byte page size, fallback to SW ECC\n",
                        ecc->size, mtd->writesize);
                ecc->mode = NAND_ECC_SOFT;
                ecc->algo = NAND_ECC_HAMMING;

        case NAND_ECC_SOFT:
                ret = nand_set_ecc_soft_ops(mtd);
                if (ret) {
                        ret = -EINVAL;
                        goto err_nand_manuf_cleanup;
                }
                break;

        case NAND_ECC_ON_DIE:
                if (!ecc->read_page || !ecc->write_page) {
                        WARN(1, "No ECC functions supplied; on-die ECC not possible\n");
                        ret = -EINVAL;
                        goto err_nand_manuf_cleanup;
                }
                if (!ecc->read_oob)
                        ecc->read_oob = nand_read_oob_std;
                if (!ecc->write_oob)
                        ecc->write_oob = nand_write_oob_std;
                break;

        case NAND_ECC_NONE:
                pr_warn("NAND_ECC_NONE selected by board driver. This is not recommended!\n");
                ecc->read_page = nand_read_page_raw;
                ecc->write_page = nand_write_page_raw;
                ecc->read_oob = nand_read_oob_std;
                ecc->read_page_raw = nand_read_page_raw;
                ecc->write_page_raw = nand_write_page_raw;
                ecc->write_oob = nand_write_oob_std;
                ecc->size = mtd->writesize;
                ecc->bytes = 0;
                ecc->strength = 0;
                break;

        default:
                WARN(1, "Invalid NAND_ECC_MODE %d\n", ecc->mode);
                ret = -EINVAL;
                goto err_nand_manuf_cleanup;
        }

        /* For many systems, the standard OOB write also works for raw */
        if (!ecc->read_oob_raw)
                ecc->read_oob_raw = ecc->read_oob;
        if (!ecc->write_oob_raw)
                ecc->write_oob_raw = ecc->write_oob;

        /* propagate ecc info to mtd_info */
        mtd->ecc_strength = ecc->strength;
        mtd->ecc_step_size = ecc->size;

        /*
         * Set the number of read / write steps for one page depending on ECC
         * mode.
         */
        ecc->steps = mtd->writesize / ecc->size;
        if (ecc->steps * ecc->size != mtd->writesize) {
                WARN(1, "Invalid ECC parameters\n");
                ret = -EINVAL;
                goto err_nand_manuf_cleanup;
        }
        ecc->total = ecc->steps * ecc->bytes;
        if (ecc->total > mtd->oobsize) {
                WARN(1, "Total number of ECC bytes exceeded oobsize\n");
                ret = -EINVAL;
                goto err_nand_manuf_cleanup;
        }

        /*
         * The number of bytes available for a client to place data into
         * the out of band area.
         */
        ret = mtd_ooblayout_count_freebytes(mtd);
        if (ret < 0)
                ret = 0;

        mtd->oobavail = ret;

        /* ECC sanity check: warn if it's too weak */
        if (!nand_ecc_strength_good(mtd))
                pr_warn("WARNING: %s: the ECC used on your system is too weak compared to the one required by the NAND chip\n",
                        mtd->name);

        /* Allow subpage writes up to ecc.steps. Not possible for MLC flash */
        if (!(chip->options & NAND_NO_SUBPAGE_WRITE) && nand_is_slc(chip)) {
                switch (ecc->steps) {
                case 2:
                        mtd->subpage_sft = 1;
                        break;
                case 4:
                case 8:
                case 16:
                        mtd->subpage_sft = 2;
                        break;
                }
        }
        chip->subpagesize = mtd->writesize >> mtd->subpage_sft;

        /* Initialize state */
        chip->state = FL_READY;

        /* Invalidate the pagebuffer reference */
        chip->pagebuf = -1;

        /* Large page NAND with SOFT_ECC should support subpage reads */
        switch (ecc->mode) {
        case NAND_ECC_SOFT:
                if (chip->page_shift > 9)
                        chip->options |= NAND_SUBPAGE_READ;
                break;

        default:
                break;
        }

        /* Fill in remaining MTD driver data */
        mtd->type = nand_is_slc(chip) ? MTD_NANDFLASH : MTD_MLCNANDFLASH;
        mtd->flags = (chip->options & NAND_ROM) ? MTD_CAP_ROM :
                                                MTD_CAP_NANDFLASH;
        mtd->_erase = nand_erase;
        mtd->_point = NULL;
        mtd->_unpoint = NULL;
        mtd->_read = nand_read;
        mtd->_write = nand_write;
        mtd->_panic_write = panic_nand_write;
        mtd->_read_oob = nand_read_oob;
        mtd->_write_oob = nand_write_oob;
        mtd->_sync = nand_sync;
        mtd->_lock = NULL;
        mtd->_unlock = NULL;
        mtd->_suspend = nand_suspend;
        mtd->_resume = nand_resume;
        mtd->_reboot = nand_shutdown;
        mtd->_block_isreserved = nand_block_isreserved;
        mtd->_block_isbad = nand_block_isbad;
        mtd->_block_markbad = nand_block_markbad;
        mtd->_max_bad_blocks = nand_max_bad_blocks;
        mtd->writebufsize = mtd->writesize;

        /*
         * Initialize bitflip_threshold to its default prior scan_bbt() call.
         * scan_bbt() might invoke mtd_read(), thus bitflip_threshold must be
         * properly set.
         */
        if (!mtd->bitflip_threshold)
                mtd->bitflip_threshold = DIV_ROUND_UP(mtd->ecc_strength * 3, 4);

        /* Initialize the ->data_interface field. */
        ret = nand_init_data_interface(chip);
        if (ret)
                goto err_nand_manuf_cleanup;

        /* Enter fastest possible mode on all dies. */
        for (i = 0; i < chip->numchips; i++) {
                chip->select_chip(mtd, i);
                ret = nand_setup_data_interface(chip, i);
                chip->select_chip(mtd, -1);

                if (ret)
                        goto err_nand_data_iface_cleanup;
        }

        /* Check, if we should skip the bad block table scan */
        if (chip->options & NAND_SKIP_BBTSCAN)
                return 0;

        /* Build bad block table */
        ret = chip->scan_bbt(mtd);
        if (ret)
                goto err_nand_data_iface_cleanup;

        return 0;

err_nand_data_iface_cleanup:
        nand_release_data_interface(chip);

err_nand_manuf_cleanup:
        nand_manufacturer_cleanup(chip);

err_free_nbuf:
        if (nbuf) {
                kfree(nbuf->databuf);
                kfree(nbuf->ecccode);
                kfree(nbuf->ecccalc);
                kfree(nbuf);
        }

        return ret;
}
EXPORT_SYMBOL(nand_scan_tail);

/*
 * is_module_text_address() isn't exported, and it's mostly a pointless
 * test if this is a module _anyway_ -- they'd have to try _really_ hard
 * to call us from in-kernel code if the core NAND support is modular.
 */
#ifdef MODULE
#define caller_is_module() (1)
#else
#define caller_is_module() \
        is_module_text_address((unsigned long)__builtin_return_address(0))
#endif

/**
 * nand_scan - [NAND Interface] Scan for the NAND device
 * @mtd: MTD device structure
 * @maxchips: number of chips to scan for
 *
 * This fills out all the uninitialized function pointers with the defaults.
 * The flash ID is read and the mtd/chip structures are filled with the
 * appropriate values.
 */
int nand_scan(struct mtd_info *mtd, int maxchips)
{
        int ret;

        ret = nand_scan_ident(mtd, maxchips, NULL);
        if (!ret)
                ret = nand_scan_tail(mtd);
        return ret;
}
EXPORT_SYMBOL(nand_scan);

/**
 * nand_cleanup - [NAND Interface] Free resources held by the NAND device
 * @chip: NAND chip object
 */
void nand_cleanup(struct nand_chip *chip)
{
        if (chip->ecc.mode == NAND_ECC_SOFT &&
            chip->ecc.algo == NAND_ECC_BCH)
                nand_bch_free((struct nand_bch_control *)chip->ecc.priv);

        nand_release_data_interface(chip);

        /* Free bad block table memory */
        kfree(chip->bbt);
        if (!(chip->options & NAND_OWN_BUFFERS) && chip->buffers) {
                kfree(chip->buffers->databuf);
                kfree(chip->buffers->ecccode);
                kfree(chip->buffers->ecccalc);
                kfree(chip->buffers);
        }

        /* Free bad block descriptor memory */
        if (chip->badblock_pattern && chip->badblock_pattern->options
                        & NAND_BBT_DYNAMICSTRUCT)
                kfree(chip->badblock_pattern);

        /* Free manufacturer priv data. */
        nand_manufacturer_cleanup(chip);
}
EXPORT_SYMBOL_GPL(nand_cleanup);

/**
 * nand_release - [NAND Interface] Unregister the MTD device and free resources
 *                held by the NAND device
 * @mtd: MTD device structure
 */
void nand_release(struct mtd_info *mtd)
{
        mtd_device_unregister(mtd);
        nand_cleanup(mtd_to_nand(mtd));
}
EXPORT_SYMBOL_GPL(nand_release);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
MODULE_AUTHOR("Thomas Gleixner <tglx@linutronix.de>");
MODULE_DESCRIPTION("Generic NAND flash driver code");