- 根目录:
- 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");