diff options
Diffstat (limited to 'drivers/iio/magnetometer/ak8975.c')
| -rw-r--r-- | drivers/iio/magnetometer/ak8975.c | 485 |
1 files changed, 485 insertions, 0 deletions
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"); |