--- /dev/null
+/*
+ * 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"
+#include "magnet.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 iio_dev *indio_dev;
+ struct attribute_group attrs;
+ struct mutex lock;
+ u8 asa[3];
+ long raw_to_gauss[3];
+ unsigned long mode;
+ u8 reg_cache[AK8975_MAX_REGS];
+ int eoc_gpio;
+ int eoc_irq;
+};
+
+/*
+ * 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)
+{
+ u8 regval;
+ struct i2c_msg msg;
+ u8 w_data[2];
+ int ret = 0;
+
+ struct ak8975_data *data = i2c_get_clientdata(client);
+
+ regval = data->reg_cache[reg];
+ regval &= ~mask;
+ regval |= val << shift;
+
+ w_data[0] = reg;
+ w_data[1] = regval;
+
+ msg.addr = client->addr;
+ msg.flags = 0;
+ msg.len = 2;
+ msg.buf = w_data;
+
+ ret = i2c_transfer(client->adapter, &msg, 1);
+ 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)
+{
+ struct i2c_msg msg[2];
+ u8 w_data[2];
+ int ret;
+
+ w_data[0] = reg;
+
+ msg[0].addr = client->addr;
+ msg[0].flags = I2C_M_NOSTART; /* set repeated start and write */
+ msg[0].len = 1;
+ msg[0].buf = w_data;
+
+ msg[1].addr = client->addr;
+ msg[1].flags = I2C_M_RD;
+ msg[1].len = length;
+ msg[1].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 for each axis and
+ store in the device data. */
+ 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 = indio_dev->dev_data;
+
+ return sprintf(buf, "%lu\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 = indio_dev->dev_data;
+ struct i2c_client *client = data->client;
+ unsigned long oval;
+ int ret;
+
+ /* Convert mode string and do some basic sanity checking on it.
+ only 0 or 1 are valid. */
+ if (strict_strtoul(buf, 10, &oval))
+ return -EINVAL;
+
+ if (oval > 1) {
+ dev_err(dev, "mode value is not supported\n");
+ return -EINVAL;
+ }
+
+ mutex_lock(&data->lock);
+
+ /* Write the mode to the device. */
+ if (data->mode != oval) {
+ ret = ak8975_write_data(client,
+ AK8975_REG_CNTL,
+ (u8)oval,
+ 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 = oval;
+ }
+
+ mutex_unlock(&data->lock);
+
+ return count;
+}
+
+/*
+ * Emits the scale factor to bring the raw value into Gauss units.
+ *
+ * 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().
+ */
+static ssize_t show_scale(struct device *dev, struct device_attribute *devattr,
+ char *buf)
+{
+ struct iio_dev *indio_dev = dev_get_drvdata(dev);
+ struct ak8975_data *data = indio_dev->dev_data;
+ struct iio_dev_attr *this_attr = to_iio_dev_attr(devattr);
+
+ return sprintf(buf, "%ld\n", data->raw_to_gauss[this_attr->address]);
+}
+
+/*
+ * Emits the raw flux value for the x, y, or z axis.
+ */
+static ssize_t show_raw(struct device *dev, struct device_attribute *devattr,
+ char *buf)
+{
+ struct iio_dev *indio_dev = dev_get_drvdata(dev);
+ struct ak8975_data *data = indio_dev->dev_data;
+ struct i2c_client *client = data->client;
+ struct iio_dev_attr *this_attr = to_iio_dev_attr(devattr);
+ u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
+ 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. */
+ 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");
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
+ if (ret < 0) {
+ dev_err(&client->dev, "Error in reading ST1\n");
+ goto exit;
+ }
+
+ 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, this_attr->address, 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);
+
+ return sprintf(buf, "%d\n", raw);
+
+exit:
+ mutex_unlock(&data->lock);
+ return ret;
+}
+
+static IIO_DEVICE_ATTR(mode, S_IRUGO | S_IWUSR, show_mode, store_mode, 0);
+static IIO_DEV_ATTR_MAGN_X_SCALE(S_IRUGO, show_scale, NULL, 0);
+static IIO_DEV_ATTR_MAGN_Y_SCALE(S_IRUGO, show_scale, NULL, 1);
+static IIO_DEV_ATTR_MAGN_Z_SCALE(S_IRUGO, show_scale, NULL, 2);
+static IIO_DEV_ATTR_MAGN_X(show_raw, AK8975_REG_HXL);
+static IIO_DEV_ATTR_MAGN_Y(show_raw, AK8975_REG_HYL);
+static IIO_DEV_ATTR_MAGN_Z(show_raw, AK8975_REG_HZL);
+
+static struct attribute *ak8975_attr[] = {
+ &iio_dev_attr_mode.dev_attr.attr,
+ &iio_dev_attr_magn_x_scale.dev_attr.attr,
+ &iio_dev_attr_magn_y_scale.dev_attr.attr,
+ &iio_dev_attr_magn_z_scale.dev_attr.attr,
+ &iio_dev_attr_magn_x_raw.dev_attr.attr,
+ &iio_dev_attr_magn_y_raw.dev_attr.attr,
+ &iio_dev_attr_magn_z_raw.dev_attr.attr,
+ NULL
+};
+
+static struct attribute_group ak8975_attr_group = {
+ .attrs = ak8975_attr,
+};
+
+static int ak8975_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct ak8975_data *data;
+ int err;
+
+ /* Allocate our device context. */
+ data = kzalloc(sizeof(struct ak8975_data), GFP_KERNEL);
+ if (!data) {
+ dev_err(&client->dev, "Memory allocation fails\n");
+ err = -ENOMEM;
+ goto exit;
+ }
+
+ i2c_set_clientdata(client, data);
+ data->client = client;
+
+ mutex_init(&data->lock);
+
+ /* Grab and set up the supplied GPIO. */
+ data->eoc_irq = client->irq;
+ data->eoc_gpio = irq_to_gpio(client->irq);
+
+ if (!data->eoc_gpio) {
+ dev_err(&client->dev, "failed, no valid GPIO\n");
+ err = -EINVAL;
+ goto exit_free;
+ }
+
+ err = gpio_request(data->eoc_gpio, "ak_8975");
+ if (err < 0) {
+ dev_err(&client->dev, "failed to request GPIO %d, error %d\n",
+ data->eoc_gpio, err);
+ goto exit_free;
+ }
+
+ err = gpio_direction_input(data->eoc_gpio);
+ if (err < 0) {
+ dev_err(&client->dev, "Failed to configure input direction for"
+ " GPIO %d, error %d\n", data->eoc_gpio, err);
+ goto exit_gpio;
+ }
+
+ /* 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;
+ }
+
+ /* Register with IIO */
+ data->indio_dev = iio_allocate_device();
+ if (data->indio_dev == NULL) {
+ err = -ENOMEM;
+ goto exit_gpio;
+ }
+
+ data->indio_dev->dev.parent = &client->dev;
+ data->indio_dev->attrs = &ak8975_attr_group;
+ data->indio_dev->dev_data = (void *)(data);
+ data->indio_dev->driver_module = THIS_MODULE;
+ data->indio_dev->modes = INDIO_DIRECT_MODE;
+
+ err = iio_device_register(data->indio_dev);
+ if (err < 0)
+ goto exit_free_iio;
+
+ return 0;
+
+exit_free_iio:
+ iio_free_device(data->indio_dev);
+exit_gpio:
+ gpio_free(data->eoc_gpio);
+exit_free:
+ kfree(data);
+exit:
+ return err;
+}
+
+static int ak8975_remove(struct i2c_client *client)
+{
+ struct ak8975_data *data = i2c_get_clientdata(client);
+
+ iio_device_unregister(data->indio_dev);
+ iio_free_device(data->indio_dev);
+
+ gpio_free(data->eoc_gpio);
+
+ kfree(data);
+
+ 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");
projects / mv-sheeva.git / blobdiff