[linux-2.6-block.git] / drivers / iio / magnetometer / ak8975.c

/*
 * A sensor driver for the magnetometer AK8975.
 *
 * Magnetic compass sensor driver for monitoring magnetic flux information.
 *
 * Copyright (c) 2010, NVIDIA Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA	02110-1301, USA.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/delay.h>

#include <linux/gpio.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
/*
 * Register definitions, as well as various shifts and masks to get at the
 * individual fields of the registers.
 */
#define AK8975_REG_WIA			0x00
#define AK8975_DEVICE_ID		0x48

#define AK8975_REG_INFO			0x01

#define AK8975_REG_ST1			0x02
#define AK8975_REG_ST1_DRDY_SHIFT	0
#define AK8975_REG_ST1_DRDY_MASK	(1 << AK8975_REG_ST1_DRDY_SHIFT)

#define AK8975_REG_HXL			0x03
#define AK8975_REG_HXH			0x04
#define AK8975_REG_HYL			0x05
#define AK8975_REG_HYH			0x06
#define AK8975_REG_HZL			0x07
#define AK8975_REG_HZH			0x08
#define AK8975_REG_ST2			0x09
#define AK8975_REG_ST2_DERR_SHIFT	2
#define AK8975_REG_ST2_DERR_MASK	(1 << AK8975_REG_ST2_DERR_SHIFT)

#define AK8975_REG_ST2_HOFL_SHIFT	3
#define AK8975_REG_ST2_HOFL_MASK	(1 << AK8975_REG_ST2_HOFL_SHIFT)

#define AK8975_REG_CNTL			0x0A
#define AK8975_REG_CNTL_MODE_SHIFT	0
#define AK8975_REG_CNTL_MODE_MASK	(0xF << AK8975_REG_CNTL_MODE_SHIFT)
#define AK8975_REG_CNTL_MODE_POWER_DOWN	0
#define AK8975_REG_CNTL_MODE_ONCE	1
#define AK8975_REG_CNTL_MODE_SELF_TEST	8
#define AK8975_REG_CNTL_MODE_FUSE_ROM	0xF

#define AK8975_REG_RSVC			0x0B
#define AK8975_REG_ASTC			0x0C
#define AK8975_REG_TS1			0x0D
#define AK8975_REG_TS2			0x0E
#define AK8975_REG_I2CDIS		0x0F
#define AK8975_REG_ASAX			0x10
#define AK8975_REG_ASAY			0x11
#define AK8975_REG_ASAZ			0x12

#define AK8975_MAX_REGS			AK8975_REG_ASAZ

/*
 * Miscellaneous values.
 */
#define AK8975_MAX_CONVERSION_TIMEOUT	500
#define AK8975_CONVERSION_DONE_POLL_TIME 10

/*
 * Per-instance context data for the device.
 */
struct ak8975_data {
	struct i2c_client	*client;
	struct attribute_group	attrs;
	struct mutex		lock;
	u8			asa[3];
	long			raw_to_gauss[3];
	u8			reg_cache[AK8975_MAX_REGS];
	int			eoc_gpio;
};

static const int ak8975_index_to_reg[] = {
	AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
};

/*
 * Helper function to write to the I2C device's registers.
 */
static int ak8975_write_data(struct i2c_client *client,
			     u8 reg, u8 val, u8 mask, u8 shift)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);
	struct ak8975_data *data = iio_priv(indio_dev);
	u8 regval;
	int ret;

	regval = (data->reg_cache[reg] & ~mask) | (val << shift);
	ret = i2c_smbus_write_byte_data(client, reg, regval);
	if (ret < 0) {
		dev_err(&client->dev, "Write to device fails status %x\n", ret);
		return ret;
	}
	data->reg_cache[reg] = regval;

	return 0;
}

/*
 * Perform some start-of-day setup, including reading the asa calibration
 * values and caching them.
 */
static int ak8975_setup(struct i2c_client *client)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);
	struct ak8975_data *data = iio_priv(indio_dev);
	u8 device_id;
	int ret;

	/* Confirm that the device we're talking to is really an AK8975. */
	ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
	if (ret < 0) {
		dev_err(&client->dev, "Error reading WIA\n");
		return ret;
	}
	device_id = ret;
	if (device_id != AK8975_DEVICE_ID) {
		dev_err(&client->dev, "Device ak8975 not found\n");
		return -ENODEV;
	}

	/* Write the fused rom access mode. */
	ret = ak8975_write_data(client,
				AK8975_REG_CNTL,
				AK8975_REG_CNTL_MODE_FUSE_ROM,
				AK8975_REG_CNTL_MODE_MASK,
				AK8975_REG_CNTL_MODE_SHIFT);
	if (ret < 0) {
		dev_err(&client->dev, "Error in setting fuse access mode\n");
		return ret;
	}

	/* Get asa data and store in the device data. */
	ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
					    3, data->asa);
	if (ret < 0) {
		dev_err(&client->dev, "Not able to read asa data\n");
		return ret;
	}

	/* After reading fuse ROM data set power-down mode */
	ret = ak8975_write_data(client,
				AK8975_REG_CNTL,
				AK8975_REG_CNTL_MODE_POWER_DOWN,
				AK8975_REG_CNTL_MODE_MASK,
				AK8975_REG_CNTL_MODE_SHIFT);
	if (ret < 0) {
		dev_err(&client->dev, "Error in setting power-down mode\n");
		return ret;
	}

/*
 * Precalculate scale factor (in Gauss units) for each axis and
 * store in the device data.
 *
 * This scale factor is axis-dependent, and is derived from 3 calibration
 * factors ASA(x), ASA(y), and ASA(z).
 *
 * These ASA values are read from the sensor device at start of day, and
 * cached in the device context struct.
 *
 * Adjusting the flux value with the sensitivity adjustment value should be
 * done via the following formula:
 *
 * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
 *
 * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
 * is the resultant adjusted value.
 *
 * We reduce the formula to:
 *
 * Hadj = H * (ASA + 128) / 256
 *
 * H is in the range of -4096 to 4095.  The magnetometer has a range of
 * +-1229uT.  To go from the raw value to uT is:
 *
 * HuT = H * 1229/4096, or roughly, 3/10.
 *
 * Since 1uT = 100 gauss, our final scale factor becomes:
 *
 * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
 * Hadj = H * ((ASA + 128) * 30 / 256
 *
 * Since ASA doesn't change, we cache the resultant scale factor into the
 * device context in ak8975_setup().
 */
	data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
	data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
	data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;

	return 0;
}

static int wait_conversion_complete_gpio(struct ak8975_data *data)
{
	struct i2c_client *client = data->client;
	u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
	int ret;

	/* Wait for the conversion to complete. */
	while (timeout_ms) {
		msleep(AK8975_CONVERSION_DONE_POLL_TIME);
		if (gpio_get_value(data->eoc_gpio))
			break;
		timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
	}
	if (!timeout_ms) {
		dev_err(&client->dev, "Conversion timeout happened\n");
		return -EINVAL;
	}

	ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
	if (ret < 0)
		dev_err(&client->dev, "Error in reading ST1\n");

	return ret;
}

static int wait_conversion_complete_polled(struct ak8975_data *data)
{
	struct i2c_client *client = data->client;
	u8 read_status;
	u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
	int ret;

	/* Wait for the conversion to complete. */
	while (timeout_ms) {
		msleep(AK8975_CONVERSION_DONE_POLL_TIME);
		ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
		if (ret < 0) {
			dev_err(&client->dev, "Error in reading ST1\n");
			return ret;
		}
		read_status = ret;
		if (read_status)
			break;
		timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
	}
	if (!timeout_ms) {
		dev_err(&client->dev, "Conversion timeout happened\n");
		return -EINVAL;
	}
	return read_status;
}

/*
 * Emits the raw flux value for the x, y, or z axis.
 */
static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
{
	struct ak8975_data *data = iio_priv(indio_dev);
	struct i2c_client *client = data->client;
	u16 meas_reg;
	s16 raw;
	int ret;

	mutex_lock(&data->lock);

	/* Set up the device for taking a sample. */
	ret = ak8975_write_data(client,
				AK8975_REG_CNTL,
				AK8975_REG_CNTL_MODE_ONCE,
				AK8975_REG_CNTL_MODE_MASK,
				AK8975_REG_CNTL_MODE_SHIFT);
	if (ret < 0) {
		dev_err(&client->dev, "Error in setting operating mode\n");
		goto exit;
	}

	/* Wait for the conversion to complete. */
	if (gpio_is_valid(data->eoc_gpio))
		ret = wait_conversion_complete_gpio(data);
	else
		ret = wait_conversion_complete_polled(data);
	if (ret < 0)
		goto exit;

	if (ret & AK8975_REG_ST1_DRDY_MASK) {
		ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
		if (ret < 0) {
			dev_err(&client->dev, "Error in reading ST2\n");
			goto exit;
		}
		if (ret & (AK8975_REG_ST2_DERR_MASK |
			   AK8975_REG_ST2_HOFL_MASK)) {
			dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
			ret = -EINVAL;
			goto exit;
		}
	}

	/* Read the flux value from the appropriate register
	   (the register is specified in the iio device attributes). */
	ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
	if (ret < 0) {
		dev_err(&client->dev, "Read axis data fails\n");
		goto exit;
	}
	meas_reg = ret;

	mutex_unlock(&data->lock);

	/* Endian conversion of the measured values. */
	raw = (s16) (le16_to_cpu(meas_reg));

	/* Clamp to valid range. */
	raw = clamp_t(s16, raw, -4096, 4095);
	*val = raw;
	return IIO_VAL_INT;

exit:
	mutex_unlock(&data->lock);
	return ret;
}

static int ak8975_read_raw(struct iio_dev *indio_dev,
			   struct iio_chan_spec const *chan,
			   int *val, int *val2,
			   long mask)
{
	struct ak8975_data *data = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		return ak8975_read_axis(indio_dev, chan->address, val);
	case IIO_CHAN_INFO_SCALE:
		*val = data->raw_to_gauss[chan->address];
		return IIO_VAL_INT;
	}
	return -EINVAL;
}

#define AK8975_CHANNEL(axis, index)					\
	{								\
		.type = IIO_MAGN,					\
		.modified = 1,						\
		.channel2 = IIO_MOD_##axis,				\
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
			     BIT(IIO_CHAN_INFO_SCALE),			\
		.address = index,					\
	}

static const struct iio_chan_spec ak8975_channels[] = {
	AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
};

static const struct iio_info ak8975_info = {
	.read_raw = &ak8975_read_raw,
	.driver_module = THIS_MODULE,
};

static int ak8975_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct ak8975_data *data;
	struct iio_dev *indio_dev;
	int eoc_gpio;
	int err;

	/* Grab and set up the supplied GPIO. */
	if (client->dev.platform_data == NULL)
		eoc_gpio = -1;
	else
		eoc_gpio = *(int *)(client->dev.platform_data);

	/* We may not have a GPIO based IRQ to scan, that is fine, we will
	   poll if so */
	if (gpio_is_valid(eoc_gpio)) {
		err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
		if (err < 0) {
			dev_err(&client->dev,
				"failed to request GPIO %d, error %d\n",
							eoc_gpio, err);
			goto exit;
		}
	}

	/* Register with IIO */
	indio_dev = iio_device_alloc(sizeof(*data));
	if (indio_dev == NULL) {
		err = -ENOMEM;
		goto exit_gpio;
	}
	data = iio_priv(indio_dev);
	i2c_set_clientdata(client, indio_dev);
	/* Perform some basic start-of-day setup of the device. */
	err = ak8975_setup(client);
	if (err < 0) {
		dev_err(&client->dev, "AK8975 initialization fails\n");
		goto exit_free_iio;
	}

	data->client = client;
	mutex_init(&data->lock);
	data->eoc_gpio = eoc_gpio;
	indio_dev->dev.parent = &client->dev;
	indio_dev->channels = ak8975_channels;
	indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
	indio_dev->info = &ak8975_info;
	indio_dev->modes = INDIO_DIRECT_MODE;

	err = iio_device_register(indio_dev);
	if (err < 0)
		goto exit_free_iio;

	return 0;

exit_free_iio:
	iio_device_free(indio_dev);
exit_gpio:
	if (gpio_is_valid(eoc_gpio))
		gpio_free(eoc_gpio);
exit:
	return err;
}

static int ak8975_remove(struct i2c_client *client)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);
	struct ak8975_data *data = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);

	if (gpio_is_valid(data->eoc_gpio))
		gpio_free(data->eoc_gpio);

	iio_device_free(indio_dev);

	return 0;
}

static const struct i2c_device_id ak8975_id[] = {
	{"ak8975", 0},
	{}
};

MODULE_DEVICE_TABLE(i2c, ak8975_id);

static const struct of_device_id ak8975_of_match[] = {
	{ .compatible = "asahi-kasei,ak8975", },
	{ .compatible = "ak8975", },
	{ }
};
MODULE_DEVICE_TABLE(of, ak8975_of_match);

static struct i2c_driver ak8975_driver = {
	.driver = {
		.name	= "ak8975",
		.of_match_table = ak8975_of_match,
	},
	.probe		= ak8975_probe,
	.remove		= ak8975_remove,
	.id_table	= ak8975_id,
};
module_i2c_driver(ak8975_driver);

MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
MODULE_DESCRIPTION("AK8975 magnetometer driver");
MODULE_LICENSE("GPL");
Commit	Line	Data
3285aae1 AC	1	/*
	2	* A sensor driver for the magnetometer AK8975.
	3	*
	4	* Magnetic compass sensor driver for monitoring magnetic flux information.
	5	*
	6	* Copyright (c) 2010, NVIDIA Corporation.
	7	*
	8	* This program is free software; you can redistribute it and/or modify
	9	* it under the terms of the GNU General Public License as published by
	10	* the Free Software Foundation; either version 2 of the License, or
	11	* (at your option) any later version.
	12	*
	13	* This program is distributed in the hope that it will be useful, but WITHOUT
	14	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	15	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
	16	* more details.
	17	*
	18	* You should have received a copy of the GNU General Public License along
	19	* with this program; if not, write to the Free Software Foundation, Inc.,
	20	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
	21	*/
	22
	23	#include <linux/module.h>
	24	#include <linux/kernel.h>
	25	#include <linux/slab.h>
	26	#include <linux/i2c.h>
	27	#include <linux/err.h>
	28	#include <linux/mutex.h>
	29	#include <linux/delay.h>
	30
	31	#include <linux/gpio.h>
	32
06458e27 JC	33	#include <linux/iio/iio.h>
06458e27 JC	34	#include <linux/iio/sysfs.h>
3285aae1 AC	35	/*
	36	* Register definitions, as well as various shifts and masks to get at the
	37	* individual fields of the registers.
	38	*/
	39	#define AK8975_REG_WIA 0x00
	40	#define AK8975_DEVICE_ID 0x48
	41
	42	#define AK8975_REG_INFO 0x01
	43
	44	#define AK8975_REG_ST1 0x02
	45	#define AK8975_REG_ST1_DRDY_SHIFT 0
	46	#define AK8975_REG_ST1_DRDY_MASK (1 << AK8975_REG_ST1_DRDY_SHIFT)
	47
	48	#define AK8975_REG_HXL 0x03
	49	#define AK8975_REG_HXH 0x04
	50	#define AK8975_REG_HYL 0x05
	51	#define AK8975_REG_HYH 0x06
	52	#define AK8975_REG_HZL 0x07
	53	#define AK8975_REG_HZH 0x08
	54	#define AK8975_REG_ST2 0x09
	55	#define AK8975_REG_ST2_DERR_SHIFT 2
	56	#define AK8975_REG_ST2_DERR_MASK (1 << AK8975_REG_ST2_DERR_SHIFT)
	57
	58	#define AK8975_REG_ST2_HOFL_SHIFT 3
	59	#define AK8975_REG_ST2_HOFL_MASK (1 << AK8975_REG_ST2_HOFL_SHIFT)
	60
	61	#define AK8975_REG_CNTL 0x0A
	62	#define AK8975_REG_CNTL_MODE_SHIFT 0
	63	#define AK8975_REG_CNTL_MODE_MASK (0xF << AK8975_REG_CNTL_MODE_SHIFT)
	64	#define AK8975_REG_CNTL_MODE_POWER_DOWN 0
	65	#define AK8975_REG_CNTL_MODE_ONCE 1
	66	#define AK8975_REG_CNTL_MODE_SELF_TEST 8
	67	#define AK8975_REG_CNTL_MODE_FUSE_ROM 0xF
	68
	69	#define AK8975_REG_RSVC 0x0B
	70	#define AK8975_REG_ASTC 0x0C
	71	#define AK8975_REG_TS1 0x0D
	72	#define AK8975_REG_TS2 0x0E
	73	#define AK8975_REG_I2CDIS 0x0F
	74	#define AK8975_REG_ASAX 0x10
	75	#define AK8975_REG_ASAY 0x11
	76	#define AK8975_REG_ASAZ 0x12
	77
	78	#define AK8975_MAX_REGS AK8975_REG_ASAZ
	79
	80	/*
	81	* Miscellaneous values.
	82	*/
	83	#define AK8975_MAX_CONVERSION_TIMEOUT 500
	84	#define AK8975_CONVERSION_DONE_POLL_TIME 10
	85
	86	/*
	87	* Per-instance context data for the device.
	88	*/
	89	struct ak8975_data {
	90	struct i2c_client *client;
3285aae1 AC	91	struct attribute_group attrs;
	92	struct mutex lock;
	93	u8 asa[3];
	94	long raw_to_gauss[3];
3285aae1 AC	95	u8 reg_cache[AK8975_MAX_REGS];
3285aae1 AC	96	int eoc_gpio;
3285aae1 AC	97	};
3285aae1 AC	98
694e1b5f JC	99	static const int ak8975_index_to_reg[] = {
	100	AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
	101	};
	102
3285aae1 AC	103	/*
	104	* Helper function to write to the I2C device's registers.
	105	*/
	106	static int ak8975_write_data(struct i2c_client *client,
	107	u8 reg, u8 val, u8 mask, u8 shift)
	108	{
40f32d93 PC	109	struct iio_dev *indio_dev = i2c_get_clientdata(client);
40f32d93 PC	110	struct ak8975_data *data = iio_priv(indio_dev);
694e1b5f JC	111	u8 regval;
694e1b5f JC	112	int ret;
3285aae1	113
694e1b5f JC	114	regval = (data->reg_cache[reg] & ~mask) \| (val << shift);
694e1b5f JC	115	ret = i2c_smbus_write_byte_data(client, reg, regval);
3285aae1 AC	116	if (ret < 0) {
	117	dev_err(&client->dev, "Write to device fails status %x\n", ret);
	118	return ret;
	119	}
	120	data->reg_cache[reg] = regval;
	121
	122	return 0;
	123	}
	124
3285aae1 AC	125	/*
	126	* Perform some start-of-day setup, including reading the asa calibration
	127	* values and caching them.
	128	*/
	129	static int ak8975_setup(struct i2c_client *client)
	130	{
40f32d93 PC	131	struct iio_dev *indio_dev = i2c_get_clientdata(client);
40f32d93 PC	132	struct ak8975_data *data = iio_priv(indio_dev);
3285aae1 AC	133	u8 device_id;
	134	int ret;
	135
	136	/* Confirm that the device we're talking to is really an AK8975. */
c411f600	137	ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
3285aae1 AC	138	if (ret < 0) {
	139	dev_err(&client->dev, "Error reading WIA\n");
	140	return ret;
	141	}
c411f600	142	device_id = ret;
3285aae1 AC	143	if (device_id != AK8975_DEVICE_ID) {
	144	dev_err(&client->dev, "Device ak8975 not found\n");
	145	return -ENODEV;
	146	}
	147
	148	/* Write the fused rom access mode. */
	149	ret = ak8975_write_data(client,
	150	AK8975_REG_CNTL,
	151	AK8975_REG_CNTL_MODE_FUSE_ROM,
	152	AK8975_REG_CNTL_MODE_MASK,
	153	AK8975_REG_CNTL_MODE_SHIFT);
	154	if (ret < 0) {
	155	dev_err(&client->dev, "Error in setting fuse access mode\n");
	156	return ret;
	157	}
	158
	159	/* Get asa data and store in the device data. */
c411f600 JC	160	ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
c411f600 JC	161	3, data->asa);
3285aae1 AC	162	if (ret < 0) {
	163	dev_err(&client->dev, "Not able to read asa data\n");
	164	return ret;
	165	}
	166
040f3e58 LA	167	/* After reading fuse ROM data set power-down mode */
	168	ret = ak8975_write_data(client,
	169	AK8975_REG_CNTL,
	170	AK8975_REG_CNTL_MODE_POWER_DOWN,
	171	AK8975_REG_CNTL_MODE_MASK,
	172	AK8975_REG_CNTL_MODE_SHIFT);
	173	if (ret < 0) {
	174	dev_err(&client->dev, "Error in setting power-down mode\n");
	175	return ret;
	176	}
	177
694e1b5f JC	178	/*
	179	* Precalculate scale factor (in Gauss units) for each axis and
	180	* store in the device data.
	181	*
	182	* This scale factor is axis-dependent, and is derived from 3 calibration
	183	* factors ASA(x), ASA(y), and ASA(z).
	184	*
	185	* These ASA values are read from the sensor device at start of day, and
	186	* cached in the device context struct.
	187	*
	188	* Adjusting the flux value with the sensitivity adjustment value should be
	189	* done via the following formula:
	190	*
	191	* Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
	192	*
	193	* where H is the raw value, ASA is the sensitivity adjustment, and Hadj
	194	* is the resultant adjusted value.
	195	*
	196	* We reduce the formula to:
	197	*
	198	* Hadj = H * (ASA + 128) / 256
	199	*
	200	* H is in the range of -4096 to 4095. The magnetometer has a range of
	201	* +-1229uT. To go from the raw value to uT is:
	202	*
	203	* HuT = H * 1229/4096, or roughly, 3/10.
	204	*
	205	* Since 1uT = 100 gauss, our final scale factor becomes:
	206	*
	207	* Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
	208	* Hadj = H * ((ASA + 128) * 30 / 256
	209	*
	210	* Since ASA doesn't change, we cache the resultant scale factor into the
	211	* device context in ak8975_setup().
	212	*/
3285aae1 AC	213	data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
	214	data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
	215	data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
	216
	217	return 0;
	218	}
	219
01fbb478 AC	220	static int wait_conversion_complete_gpio(struct ak8975_data *data)
	221	{
	222	struct i2c_client *client = data->client;
01fbb478 AC	223	u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
	224	int ret;
	225
	226	/* Wait for the conversion to complete. */
	227	while (timeout_ms) {
	228	msleep(AK8975_CONVERSION_DONE_POLL_TIME);
	229	if (gpio_get_value(data->eoc_gpio))
	230	break;
	231	timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
	232	}
	233	if (!timeout_ms) {
	234	dev_err(&client->dev, "Conversion timeout happened\n");
	235	return -EINVAL;
	236	}
	237
c411f600 JC	238	ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
c411f600 JC	239	if (ret < 0)
01fbb478	240	dev_err(&client->dev, "Error in reading ST1\n");
c411f600 JC	241
c411f600 JC	242	return ret;
01fbb478 AC	243	}
	244
	245	static int wait_conversion_complete_polled(struct ak8975_data *data)
	246	{
	247	struct i2c_client *client = data->client;
	248	u8 read_status;
	249	u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
	250	int ret;
	251
	252	/* Wait for the conversion to complete. */
	253	while (timeout_ms) {
	254	msleep(AK8975_CONVERSION_DONE_POLL_TIME);
c411f600	255	ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
01fbb478 AC	256	if (ret < 0) {
	257	dev_err(&client->dev, "Error in reading ST1\n");
	258	return ret;
	259	}
c411f600	260	read_status = ret;
01fbb478 AC	261	if (read_status)
	262	break;
	263	timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
	264	}
	265	if (!timeout_ms) {
	266	dev_err(&client->dev, "Conversion timeout happened\n");
	267	return -EINVAL;
	268	}
	269	return read_status;
	270	}
	271
3285aae1 AC	272	/*
	273	* Emits the raw flux value for the x, y, or z axis.
	274	*/
694e1b5f	275	static int ak8975_read_axis(struct iio_dev indio_dev, int index, int val)
3285aae1	276	{
338473c8	277	struct ak8975_data *data = iio_priv(indio_dev);
3285aae1	278	struct i2c_client *client = data->client;
3285aae1 AC	279	u16 meas_reg;
3285aae1 AC	280	s16 raw;
3285aae1 AC	281	int ret;
	282
	283	mutex_lock(&data->lock);
	284
3285aae1 AC	285	/* Set up the device for taking a sample. */
	286	ret = ak8975_write_data(client,
	287	AK8975_REG_CNTL,
	288	AK8975_REG_CNTL_MODE_ONCE,
	289	AK8975_REG_CNTL_MODE_MASK,
	290	AK8975_REG_CNTL_MODE_SHIFT);
	291	if (ret < 0) {
	292	dev_err(&client->dev, "Error in setting operating mode\n");
	293	goto exit;
	294	}
	295
	296	/* Wait for the conversion to complete. */
7c6c9368	297	if (gpio_is_valid(data->eoc_gpio))
01fbb478 AC	298	ret = wait_conversion_complete_gpio(data);
	299	else
	300	ret = wait_conversion_complete_polled(data);
	301	if (ret < 0)
3285aae1	302	goto exit;
3285aae1	303
c411f600 JC	304	if (ret & AK8975_REG_ST1_DRDY_MASK) {
c411f600 JC	305	ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
3285aae1 AC	306	if (ret < 0) {
	307	dev_err(&client->dev, "Error in reading ST2\n");
	308	goto exit;
	309	}
c411f600 JC	310	if (ret & (AK8975_REG_ST2_DERR_MASK \|
	311	AK8975_REG_ST2_HOFL_MASK)) {
	312	dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
3285aae1 AC	313	ret = -EINVAL;
	314	goto exit;
	315	}
	316	}
	317
	318	/* Read the flux value from the appropriate register
	319	(the register is specified in the iio device attributes). */
c411f600	320	ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
3285aae1 AC	321	if (ret < 0) {
	322	dev_err(&client->dev, "Read axis data fails\n");
	323	goto exit;
	324	}
c411f600	325	meas_reg = ret;
3285aae1 AC	326
	327	mutex_unlock(&data->lock);
	328
	329	/* Endian conversion of the measured values. */
	330	raw = (s16) (le16_to_cpu(meas_reg));
	331
	332	/* Clamp to valid range. */
	333	raw = clamp_t(s16, raw, -4096, 4095);
694e1b5f JC	334	*val = raw;
694e1b5f JC	335	return IIO_VAL_INT;
3285aae1 AC	336
	337	exit:
	338	mutex_unlock(&data->lock);
	339	return ret;
	340	}
	341
694e1b5f JC	342	static int ak8975_read_raw(struct iio_dev *indio_dev,
	343	struct iio_chan_spec const *chan,
	344	int val, int val2,
	345	long mask)
	346	{
	347	struct ak8975_data *data = iio_priv(indio_dev);
	348
	349	switch (mask) {
4d9948b3	350	case IIO_CHAN_INFO_RAW:
694e1b5f	351	return ak8975_read_axis(indio_dev, chan->address, val);
c8a9f805	352	case IIO_CHAN_INFO_SCALE:
694e1b5f JC	353	*val = data->raw_to_gauss[chan->address];
	354	return IIO_VAL_INT;
	355	}
	356	return -EINVAL;
	357	}
	358
	359	#define AK8975_CHANNEL(axis, index) \
	360	{ \
	361	.type = IIO_MAGN, \
	362	.modified = 1, \
	363	.channel2 = IIO_MOD_##axis, \
3a0b4422 JC	364	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) \| \
3a0b4422 JC	365	BIT(IIO_CHAN_INFO_SCALE), \
694e1b5f JC	366	.address = index, \
	367	}
	368
	369	static const struct iio_chan_spec ak8975_channels[] = {
	370	AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
	371	};
	372
6fe8135f	373	static const struct iio_info ak8975_info = {
694e1b5f	374	.read_raw = &ak8975_read_raw,
6fe8135f JC	375	.driver_module = THIS_MODULE,
	376	};
	377
4ae1c61f	378	static int ak8975_probe(struct i2c_client *client,
3285aae1 AC	379	const struct i2c_device_id *id)
	380	{
	381	struct ak8975_data *data;
338473c8 JC	382	struct iio_dev *indio_dev;
338473c8 JC	383	int eoc_gpio;
3285aae1 AC	384	int err;
3285aae1 AC	385
3285aae1	386	/* Grab and set up the supplied GPIO. */
f6d838d7 JC	387	if (client->dev.platform_data == NULL)
	388	eoc_gpio = -1;
	389	else
	390	eoc_gpio = (int )(client->dev.platform_data);
3285aae1	391
01fbb478 AC	392	/* We may not have a GPIO based IRQ to scan, that is fine, we will
01fbb478 AC	393	poll if so */
7c6c9368	394	if (gpio_is_valid(eoc_gpio)) {
82f2acdc	395	err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
01fbb478 AC	396	if (err < 0) {
	397	dev_err(&client->dev,
	398	"failed to request GPIO %d, error %d\n",
338473c8 JC	399	eoc_gpio, err);
338473c8 JC	400	goto exit;
01fbb478	401	}
7c6c9368	402	}
3285aae1	403
338473c8	404	/* Register with IIO */
7cbb7537	405	indio_dev = iio_device_alloc(sizeof(*data));
338473c8 JC	406	if (indio_dev == NULL) {
	407	err = -ENOMEM;
	408	goto exit_gpio;
	409	}
	410	data = iio_priv(indio_dev);
40f32d93	411	i2c_set_clientdata(client, indio_dev);
3285aae1 AC	412	/* Perform some basic start-of-day setup of the device. */
	413	err = ak8975_setup(client);
	414	if (err < 0) {
	415	dev_err(&client->dev, "AK8975 initialization fails\n");
ad31d250	416	goto exit_free_iio;
3285aae1 AC	417	}
3285aae1 AC	418
338473c8 JC	419	data->client = client;
338473c8 JC	420	mutex_init(&data->lock);
338473c8 JC	421	data->eoc_gpio = eoc_gpio;
338473c8 JC	422	indio_dev->dev.parent = &client->dev;
694e1b5f JC	423	indio_dev->channels = ak8975_channels;
694e1b5f JC	424	indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
338473c8 JC	425	indio_dev->info = &ak8975_info;
338473c8 JC	426	indio_dev->modes = INDIO_DIRECT_MODE;
3285aae1	427
338473c8	428	err = iio_device_register(indio_dev);
3285aae1 AC	429	if (err < 0)
	430	goto exit_free_iio;
	431
	432	return 0;
	433
	434	exit_free_iio:
7cbb7537	435	iio_device_free(indio_dev);
3285aae1	436	exit_gpio:
7c6c9368	437	if (gpio_is_valid(eoc_gpio))
338473c8	438	gpio_free(eoc_gpio);
3285aae1 AC	439	exit:
	440	return err;
	441	}
	442
447d4f29	443	static int ak8975_remove(struct i2c_client *client)
3285aae1	444	{
338473c8 JC	445	struct iio_dev *indio_dev = i2c_get_clientdata(client);
338473c8 JC	446	struct ak8975_data *data = iio_priv(indio_dev);
3285aae1	447
338473c8	448	iio_device_unregister(indio_dev);
3285aae1	449
d2fffd6c JC	450	if (gpio_is_valid(data->eoc_gpio))
	451	gpio_free(data->eoc_gpio);
	452
7cbb7537	453	iio_device_free(indio_dev);
3285aae1 AC	454
	455	return 0;
	456	}
	457
	458	static const struct i2c_device_id ak8975_id[] = {
	459	{"ak8975", 0},
	460	{}
	461	};
	462
	463	MODULE_DEVICE_TABLE(i2c, ak8975_id);
	464
54461c30 OJ	465	static const struct of_device_id ak8975_of_match[] = {
	466	{ .compatible = "asahi-kasei,ak8975", },
	467	{ .compatible = "ak8975", },
	468	{ }
	469	};
	470	MODULE_DEVICE_TABLE(of, ak8975_of_match);
	471
3285aae1 AC	472	static struct i2c_driver ak8975_driver = {
	473	.driver = {
	474	.name = "ak8975",
54461c30	475	.of_match_table = ak8975_of_match,
3285aae1 AC	476	},
3285aae1 AC	477	.probe = ak8975_probe,
e543acf0	478	.remove = ak8975_remove,
3285aae1 AC	479	.id_table = ak8975_id,
3285aae1 AC	480	};
6e5af184	481	module_i2c_driver(ak8975_driver);
3285aae1 AC	482
	483	MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
	484	MODULE_DESCRIPTION("AK8975 magnetometer driver");
	485	MODULE_LICENSE("GPL");