ak8975.c

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/*
 * 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;
    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 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;
}

/*
 * 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 = &reg,
        }, {
            .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 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 = 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;
    }

    /* 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;
    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);

    /* 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;

    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 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 = IIO_CHAN_INFO_RAW_SEPARATE_BIT |       \
                 IIO_CHAN_INFO_SCALE_SEPARATE_BIT,      \
        .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 __devinit 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_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_device_free(indio_dev);
exit_gpio:
    if (gpio_is_valid(eoc_gpio))
        gpio_free(eoc_gpio);
exit:
    return err;
}

static int __devexit 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     = __devexit_p(ak8975_remove),
    .id_table   = ak8975_id,
};
module_i2c_driver(ak8975_driver);

MODULE_AUTHOR("Laxman Dewangan <[email protected]>");
MODULE_DESCRIPTION("AK8975 magnetometer driver");
MODULE_LICENSE("GPL");