3 files changed, 497 insertions, 0 deletions

diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
index cd29be54f643..bd1cfb666695 100644
--- a/drivers/iio/magnetometer/Kconfig
+++ b/drivers/iio/magnetometer/Kconfig
@@ -3,6 +3,17 @@
 #
 menu "Magnetometer sensors"
 
+config AK8975
+        tristate "Asahi Kasei AK8975 3-Axis Magnetometer"
+        depends on I2C
+        depends on GPIOLIB
+        help
+          Say yes here to build support for Asahi Kasei AK8975 3-Axis
+          Magnetometer.
+
+          To compile this driver as a module, choose M here: the module
+          will be called ak8975.
+
 config HID_SENSOR_MAGNETOMETER_3D
         depends on HID_SENSOR_HUB
         select IIO_BUFFER
diff --git a/drivers/iio/magnetometer/Makefile b/drivers/iio/magnetometer/Makefile
index e78672876dc2..7f328e37fbab 100644
--- a/drivers/iio/magnetometer/Makefile
+++ b/drivers/iio/magnetometer/Makefile
@@ -2,6 +2,7 @@
 # Makefile for industrial I/O Magnetometer sensor drivers
 #
 
+obj-$(CONFIG_AK8975)    += ak8975.o
 obj-$(CONFIG_HID_SENSOR_MAGNETOMETER_3D) += hid-sensor-magn-3d.o
 
 obj-$(CONFIG_IIO_ST_MAGN_3AXIS) += st_magn.o
diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
new file mode 100644
index 000000000000..af6c320a534e
--- /dev/null
+++ b/drivers/iio/magnetometer/ak8975.c
@@ -0,0 +1,485 @@
+/*
+ * 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");