590 lines
14 KiB
C
590 lines
14 KiB
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 "../iio.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];
|
|
bool mode;
|
|
u8 reg_cache[AK8975_MAX_REGS];
|
|
int eoc_gpio;
|
|
int eoc_irq;
|
|
};
|
|
|
|
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 ak8975_data *data = i2c_get_clientdata(client);
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* Helper function to read a contiguous set of the I2C device's registers.
|
|
*/
|
|
static int ak8975_read_data(struct i2c_client *client,
|
|
u8 reg, u8 length, u8 *buffer)
|
|
{
|
|
int ret;
|
|
struct i2c_msg msg[2] = {
|
|
{
|
|
.addr = client->addr,
|
|
.flags = I2C_M_NOSTART,
|
|
.len = 1,
|
|
.buf = ®,
|
|
}, {
|
|
.addr = client->addr,
|
|
.flags = I2C_M_RD,
|
|
.len = length,
|
|
.buf = buffer,
|
|
}
|
|
};
|
|
|
|
ret = i2c_transfer(client->adapter, msg, 2);
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Read from device fails\n");
|
|
return ret;
|
|
}
|
|
|
|
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 ak8975_data *data = i2c_get_clientdata(client);
|
|
u8 device_id;
|
|
int ret;
|
|
|
|
/* Confirm that the device we're talking to is really an AK8975. */
|
|
ret = ak8975_read_data(client, AK8975_REG_WIA, 1, &device_id);
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Error reading WIA\n");
|
|
return 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 = ak8975_read_data(client, AK8975_REG_ASAX, 3, data->asa);
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Not able to read asa data\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;
|
|
}
|
|
|
|
/*
|
|
* Shows the device's mode. 0 = off, 1 = on.
|
|
*/
|
|
static ssize_t show_mode(struct device *dev, struct device_attribute *devattr,
|
|
char *buf)
|
|
{
|
|
struct iio_dev *indio_dev = dev_get_drvdata(dev);
|
|
struct ak8975_data *data = iio_priv(indio_dev);
|
|
|
|
return sprintf(buf, "%u\n", data->mode);
|
|
}
|
|
|
|
/*
|
|
* Sets the device's mode. 0 = off, 1 = on. The device's mode must be on
|
|
* for the magn raw attributes to be available.
|
|
*/
|
|
static ssize_t store_mode(struct device *dev, struct device_attribute *devattr,
|
|
const char *buf, size_t count)
|
|
{
|
|
struct iio_dev *indio_dev = dev_get_drvdata(dev);
|
|
struct ak8975_data *data = iio_priv(indio_dev);
|
|
struct i2c_client *client = data->client;
|
|
bool value;
|
|
int ret;
|
|
|
|
/* Convert mode string and do some basic sanity checking on it.
|
|
only 0 or 1 are valid. */
|
|
ret = strtobool(buf, &value);
|
|
if (ret < 0)
|
|
return ret;
|
|
|
|
mutex_lock(&data->lock);
|
|
|
|
/* Write the mode to the device. */
|
|
if (data->mode != value) {
|
|
ret = ak8975_write_data(client,
|
|
AK8975_REG_CNTL,
|
|
(u8)value,
|
|
AK8975_REG_CNTL_MODE_MASK,
|
|
AK8975_REG_CNTL_MODE_SHIFT);
|
|
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Error in setting mode\n");
|
|
mutex_unlock(&data->lock);
|
|
return ret;
|
|
}
|
|
data->mode = value;
|
|
}
|
|
|
|
mutex_unlock(&data->lock);
|
|
|
|
return count;
|
|
}
|
|
|
|
static int wait_conversion_complete_gpio(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);
|
|
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 = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Error in reading ST1\n");
|
|
return ret;
|
|
}
|
|
return read_status;
|
|
}
|
|
|
|
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 = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Error in reading ST1\n");
|
|
return 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;
|
|
u8 read_status;
|
|
int ret;
|
|
|
|
mutex_lock(&data->lock);
|
|
|
|
if (data->mode == 0) {
|
|
dev_err(&client->dev, "Operating mode is in power down mode\n");
|
|
ret = -EBUSY;
|
|
goto exit;
|
|
}
|
|
|
|
/* 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 (data->eoc_gpio)
|
|
ret = wait_conversion_complete_gpio(data);
|
|
else
|
|
ret = wait_conversion_complete_polled(data);
|
|
if (ret < 0)
|
|
goto exit;
|
|
|
|
read_status = ret;
|
|
|
|
if (read_status & AK8975_REG_ST1_DRDY_MASK) {
|
|
ret = ak8975_read_data(client, AK8975_REG_ST2, 1, &read_status);
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Error in reading ST2\n");
|
|
goto exit;
|
|
}
|
|
if (read_status & (AK8975_REG_ST2_DERR_MASK |
|
|
AK8975_REG_ST2_HOFL_MASK)) {
|
|
dev_err(&client->dev, "ST2 status error 0x%x\n",
|
|
read_status);
|
|
ret = -EINVAL;
|
|
goto exit;
|
|
}
|
|
}
|
|
|
|
/* Read the flux value from the appropriate register
|
|
(the register is specified in the iio device attributes). */
|
|
ret = ak8975_read_data(client, ak8975_index_to_reg[index],
|
|
2, (u8 *)&meas_reg);
|
|
if (ret < 0) {
|
|
dev_err(&client->dev, "Read axis data fails\n");
|
|
goto exit;
|
|
}
|
|
|
|
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 0:
|
|
return ak8975_read_axis(indio_dev, chan->address, val);
|
|
case (1 << IIO_CHAN_INFO_SCALE_SEPARATE):
|
|
*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 = (1 << IIO_CHAN_INFO_SCALE_SEPARATE), \
|
|
.address = index, \
|
|
}
|
|
|
|
static const struct iio_chan_spec ak8975_channels[] = {
|
|
AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
|
|
};
|
|
|
|
static IIO_DEVICE_ATTR(mode, S_IRUGO | S_IWUSR, show_mode, store_mode, 0);
|
|
|
|
static struct attribute *ak8975_attr[] = {
|
|
&iio_dev_attr_mode.dev_attr.attr,
|
|
NULL
|
|
};
|
|
|
|
static struct attribute_group ak8975_attr_group = {
|
|
.attrs = ak8975_attr,
|
|
};
|
|
|
|
static const struct iio_info ak8975_info = {
|
|
.attrs = &ak8975_attr_group,
|
|
.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. */
|
|
eoc_gpio = irq_to_gpio(client->irq);
|
|
|
|
/* We may not have a GPIO based IRQ to scan, that is fine, we will
|
|
poll if so */
|
|
if (eoc_gpio > 0) {
|
|
err = gpio_request(eoc_gpio, "ak_8975");
|
|
if (err < 0) {
|
|
dev_err(&client->dev,
|
|
"failed to request GPIO %d, error %d\n",
|
|
eoc_gpio, err);
|
|
goto exit;
|
|
}
|
|
|
|
err = gpio_direction_input(eoc_gpio);
|
|
if (err < 0) {
|
|
dev_err(&client->dev,
|
|
"Failed to configure input direction for GPIO %d, error %d\n",
|
|
eoc_gpio, err);
|
|
goto exit_gpio;
|
|
}
|
|
} else
|
|
eoc_gpio = 0; /* No GPIO available */
|
|
|
|
/* Register with IIO */
|
|
indio_dev = iio_allocate_device(sizeof(*data));
|
|
if (indio_dev == NULL) {
|
|
err = -ENOMEM;
|
|
goto exit_gpio;
|
|
}
|
|
data = iio_priv(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_gpio;
|
|
}
|
|
|
|
i2c_set_clientdata(client, indio_dev);
|
|
data->client = client;
|
|
mutex_init(&data->lock);
|
|
data->eoc_irq = client->irq;
|
|
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_free_device(indio_dev);
|
|
exit_gpio:
|
|
if (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);
|
|
int eoc_gpio = data->eoc_gpio;
|
|
|
|
iio_device_unregister(indio_dev);
|
|
iio_free_device(indio_dev);
|
|
|
|
if (eoc_gpio)
|
|
gpio_free(eoc_gpio);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static const struct i2c_device_id ak8975_id[] = {
|
|
{"ak8975", 0},
|
|
{}
|
|
};
|
|
|
|
MODULE_DEVICE_TABLE(i2c, ak8975_id);
|
|
|
|
static struct i2c_driver ak8975_driver = {
|
|
.driver = {
|
|
.name = "ak8975",
|
|
},
|
|
.probe = ak8975_probe,
|
|
.remove = __devexit_p(ak8975_remove),
|
|
.id_table = ak8975_id,
|
|
};
|
|
|
|
static int __init ak8975_init(void)
|
|
{
|
|
return i2c_add_driver(&ak8975_driver);
|
|
}
|
|
|
|
static void __exit ak8975_exit(void)
|
|
{
|
|
i2c_del_driver(&ak8975_driver);
|
|
}
|
|
|
|
module_init(ak8975_init);
|
|
module_exit(ak8975_exit);
|
|
|
|
MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
|
|
MODULE_DESCRIPTION("AK8975 magnetometer driver");
|
|
MODULE_LICENSE("GPL");
|