drivers/misc/aspeed-lpc-snoop.c

   1 /*
   2  * Copyright 2017 Google Inc
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  *
   9  * Provides a simple driver to control the ASPEED LPC snoop interface which
  10  * allows the BMC to listen on and save the data written by
  11  * the host to an arbitrary LPC I/O port.
  12  *
  13  * Typically used by the BMC to "watch" host boot progress via port
  14  * 0x80 writes made by the BIOS during the boot process.
  15  */
  16
  17 #include <linux/bitops.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/fs.h>
  20 #include <linux/kfifo.h>
  21 #include <linux/mfd/syscon.h>
  22 #include <linux/miscdevice.h>
  23 #include <linux/module.h>
  24 #include <linux/of.h>
  25 #include <linux/of_device.h>
  26 #include <linux/platform_device.h>
  27 #include <linux/poll.h>
  28 #include <linux/regmap.h>
  29
  30 #define DEVICE_NAME     "aspeed-lpc-snoop"
  31
  32 #define NUM_SNOOP_CHANNELS 2
  33 #define SNOOP_FIFO_SIZE 2048
  34
  35 #define HICR5   0x0
  36 #define HICR5_EN_SNP0W          BIT(0)
  37 #define HICR5_ENINT_SNP0W       BIT(1)
  38 #define HICR5_EN_SNP1W          BIT(2)
  39 #define HICR5_ENINT_SNP1W       BIT(3)
  40
  41 #define HICR6   0x4
  42 #define HICR6_STR_SNP0W         BIT(0)
  43 #define HICR6_STR_SNP1W         BIT(1)
  44 #define SNPWADR 0x10
  45 #define SNPWADR_CH0_MASK        GENMASK(15, 0)
  46 #define SNPWADR_CH0_SHIFT       0
  47 #define SNPWADR_CH1_MASK        GENMASK(31, 16)
  48 #define SNPWADR_CH1_SHIFT       16
  49 #define SNPWDR  0x14
  50 #define SNPWDR_CH0_MASK         GENMASK(7, 0)
  51 #define SNPWDR_CH0_SHIFT        0
  52 #define SNPWDR_CH1_MASK         GENMASK(15, 8)
  53 #define SNPWDR_CH1_SHIFT        8
  54 #define HICRB   0x80
  55 #define HICRB_ENSNP0D           BIT(14)
  56 #define HICRB_ENSNP1D           BIT(15)
  57
  58 struct aspeed_lpc_snoop_model_data {
  59         /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
  60          * can use them.
  61          */
  62         unsigned int has_hicrb_ensnp;
  63 };
  64
  65 struct aspeed_lpc_snoop_channel {
  66         struct kfifo            fifo;
  67         wait_queue_head_t       wq;
  68         struct miscdevice       miscdev;
  69 };
  70
  71 struct aspeed_lpc_snoop {
  72         struct regmap           *regmap;
  73         int                     irq;
  74         struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
  75 };
  76
  77 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
  78 {
  79         return container_of(file->private_data,
  80                             struct aspeed_lpc_snoop_channel,
  81                             miscdev);
  82 }
  83
  84 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
  85                                 size_t count, loff_t *ppos)
  86 {
  87         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
  88         unsigned int copied;
  89         int ret = 0;
  90
  91         if (kfifo_is_empty(&chan->fifo)) {
  92                 if (file->f_flags & O_NONBLOCK)
  93                         return -EAGAIN;
  94                 ret = wait_event_interruptible(chan->wq,
  95                                 !kfifo_is_empty(&chan->fifo));
  96                 if (ret == -ERESTARTSYS)
  97                         return -EINTR;
  98         }
  99         ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
 100
 101         return ret ? ret : copied;
 102 }
 103
 104 static unsigned int snoop_file_poll(struct file *file,
 105                                     struct poll_table_struct *pt)
 106 {
 107         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
 108
 109         poll_wait(file, &chan->wq, pt);
 110         return !kfifo_is_empty(&chan->fifo) ? POLLIN : 0;
 111 }
 112
 113 static const struct file_operations snoop_fops = {
 114         .owner  = THIS_MODULE,
 115         .read   = snoop_file_read,
 116         .poll   = snoop_file_poll,
 117         .llseek = noop_llseek,
 118 };
 119
 120 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
 121 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
 122 {
 123         if (!kfifo_initialized(&chan->fifo))
 124                 return;
 125         if (kfifo_is_full(&chan->fifo))
 126                 kfifo_skip(&chan->fifo);
 127         kfifo_put(&chan->fifo, val);
 128         wake_up_interruptible(&chan->wq);
 129 }
 130
 131 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
 132 {
 133         struct aspeed_lpc_snoop *lpc_snoop = arg;
 134         u32 reg, data;
 135
 136         if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
 137                 return IRQ_NONE;
 138
 139         /* Check if one of the snoop channels is interrupting */
 140         reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
 141         if (!reg)
 142                 return IRQ_NONE;
 143
 144         /* Ack pending IRQs */
 145         regmap_write(lpc_snoop->regmap, HICR6, reg);
 146
 147         /* Read and save most recent snoop'ed data byte to FIFO */
 148         regmap_read(lpc_snoop->regmap, SNPWDR, &data);
 149
 150         if (reg & HICR6_STR_SNP0W) {
 151                 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
 152
 153                 put_fifo_with_discard(&lpc_snoop->chan[0], val);
 154         }
 155         if (reg & HICR6_STR_SNP1W) {
 156                 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
 157
 158                 put_fifo_with_discard(&lpc_snoop->chan[1], val);
 159         }
 160
 161         return IRQ_HANDLED;
 162 }
 163
 164 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
 165                                        struct platform_device *pdev)
 166 {
 167         struct device *dev = &pdev->dev;
 168         int rc;
 169
 170         lpc_snoop->irq = platform_get_irq(pdev, 0);
 171         if (!lpc_snoop->irq)
 172                 return -ENODEV;
 173
 174         rc = devm_request_irq(dev, lpc_snoop->irq,
 175                               aspeed_lpc_snoop_irq, IRQF_SHARED,
 176                               DEVICE_NAME, lpc_snoop);
 177         if (rc < 0) {
 178                 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
 179                 lpc_snoop->irq = 0;
 180                 return rc;
 181         }
 182
 183         return 0;
 184 }
 185
 186 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 187                                    struct device *dev,
 188                                    int channel, u16 lpc_port)
 189 {
 190         int rc = 0;
 191         u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
 192         const struct aspeed_lpc_snoop_model_data *model_data =
 193                 of_device_get_match_data(dev);
 194
 195         init_waitqueue_head(&lpc_snoop->chan[channel].wq);
 196         /* Create FIFO datastructure */
 197         rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
 198                          SNOOP_FIFO_SIZE, GFP_KERNEL);
 199         if (rc)
 200                 return rc;
 201
 202         lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
 203         lpc_snoop->chan[channel].miscdev.name =
 204                 devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
 205         lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
 206         lpc_snoop->chan[channel].miscdev.parent = dev;
 207         rc = misc_register(&lpc_snoop->chan[channel].miscdev);
 208         if (rc)
 209                 return rc;
 210
 211         /* Enable LPC snoop channel at requested port */
 212         switch (channel) {
 213         case 0:
 214                 hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
 215                 snpwadr_mask = SNPWADR_CH0_MASK;
 216                 snpwadr_shift = SNPWADR_CH0_SHIFT;
 217                 hicrb_en = HICRB_ENSNP0D;
 218                 break;
 219         case 1:
 220                 hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
 221                 snpwadr_mask = SNPWADR_CH1_MASK;
 222                 snpwadr_shift = SNPWADR_CH1_SHIFT;
 223                 hicrb_en = HICRB_ENSNP1D;
 224                 break;
 225         default:
 226                 return -EINVAL;
 227         }
 228
 229         regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
 230         regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
 231                            lpc_port << snpwadr_shift);
 232         if (model_data->has_hicrb_ensnp)
 233                 regmap_update_bits(lpc_snoop->regmap, HICRB,
 234                                 hicrb_en, hicrb_en);
 235
 236         return rc;
 237 }
 238
 239 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 240                                      int channel)
 241 {
 242         switch (channel) {
 243         case 0:
 244                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 245                                    HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
 246                                    0);
 247                 break;
 248         case 1:
 249                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 250                                    HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
 251                                    0);
 252                 break;
 253         default:
 254                 return;
 255         }
 256
 257         kfifo_free(&lpc_snoop->chan[channel].fifo);
 258         misc_deregister(&lpc_snoop->chan[channel].miscdev);
 259 }
 260
 261 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
 262 {
 263         struct aspeed_lpc_snoop *lpc_snoop;
 264         struct device *dev;
 265         u32 port;
 266         int rc;
 267
 268         dev = &pdev->dev;
 269
 270         lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
 271         if (!lpc_snoop)
 272                 return -ENOMEM;
 273
 274         lpc_snoop->regmap = syscon_node_to_regmap(
 275                         pdev->dev.parent->of_node);
 276         if (IS_ERR(lpc_snoop->regmap)) {
 277                 dev_err(dev, "Couldn't get regmap\n");
 278                 return -ENODEV;
 279         }
 280
 281         dev_set_drvdata(&pdev->dev, lpc_snoop);
 282
 283         rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
 284         if (rc) {
 285                 dev_err(dev, "no snoop ports configured\n");
 286                 return -ENODEV;
 287         }
 288
 289         rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
 290         if (rc)
 291                 return rc;
 292
 293         rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
 294         if (rc)
 295                 return rc;
 296
 297         /* Configuration of 2nd snoop channel port is optional */
 298         if (of_property_read_u32_index(dev->of_node, "snoop-ports",
 299                                        1, &port) == 0) {
 300                 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
 301                 if (rc)
 302                         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 303         }
 304
 305         return rc;
 306 }
 307
 308 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
 309 {
 310         struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
 311
 312         /* Disable both snoop channels */
 313         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 314         aspeed_lpc_disable_snoop(lpc_snoop, 1);
 315
 316         return 0;
 317 }
 318
 319 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
 320         .has_hicrb_ensnp = 0,
 321 };
 322
 323 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
 324         .has_hicrb_ensnp = 1,
 325 };
 326
 327 static const struct of_device_id aspeed_lpc_snoop_match[] = {
 328         { .compatible = "aspeed,ast2400-lpc-snoop",
 329           .data = &ast2400_model_data },
 330         { .compatible = "aspeed,ast2500-lpc-snoop",
 331           .data = &ast2500_model_data },
 332         { },
 333 };
 334
 335 static struct platform_driver aspeed_lpc_snoop_driver = {
 336         .driver = {
 337                 .name           = DEVICE_NAME,
 338                 .of_match_table = aspeed_lpc_snoop_match,
 339         },
 340         .probe = aspeed_lpc_snoop_probe,
 341         .remove = aspeed_lpc_snoop_remove,
 342 };
 343
 344 module_platform_driver(aspeed_lpc_snoop_driver);
 345
 346 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
 347 MODULE_LICENSE("GPL");
 348 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
 349 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");