drivers/iio/pressure/bmp280.c

/*
 * Copyright (c) 2014 Intel Corporation
 *
 * Driver for Bosch Sensortec BMP280 digital pressure sensor.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) "bmp280: " fmt

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/acpi.h>
#include <linux/regmap.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

#define BMP280_REG_TEMP_XLSB		0xFC
#define BMP280_REG_TEMP_LSB		0xFB
#define BMP280_REG_TEMP_MSB		0xFA
#define BMP280_REG_PRESS_XLSB		0xF9
#define BMP280_REG_PRESS_LSB		0xF8
#define BMP280_REG_PRESS_MSB		0xF7

#define BMP280_REG_CONFIG		0xF5
#define BMP280_REG_CTRL_MEAS		0xF4
#define BMP280_REG_STATUS		0xF3
#define BMP280_REG_RESET		0xE0
#define BMP280_REG_ID			0xD0

#define BMP280_REG_COMP_TEMP_START	0x88
#define BMP280_COMP_TEMP_REG_COUNT	6

#define BMP280_REG_COMP_PRESS_START	0x8E
#define BMP280_COMP_PRESS_REG_COUNT	18

#define BMP280_FILTER_MASK		(BIT(4) | BIT(3) | BIT(2))
#define BMP280_FILTER_OFF		0
#define BMP280_FILTER_2X		BIT(2)
#define BMP280_FILTER_4X		BIT(3)
#define BMP280_FILTER_8X		(BIT(3) | BIT(2))
#define BMP280_FILTER_16X		BIT(4)

#define BMP280_OSRS_TEMP_MASK		(BIT(7) | BIT(6) | BIT(5))
#define BMP280_OSRS_TEMP_SKIP		0
#define BMP280_OSRS_TEMP_1X		BIT(5)
#define BMP280_OSRS_TEMP_2X		BIT(6)
#define BMP280_OSRS_TEMP_4X		(BIT(6) | BIT(5))
#define BMP280_OSRS_TEMP_8X		BIT(7)
#define BMP280_OSRS_TEMP_16X		(BIT(7) | BIT(5))

#define BMP280_OSRS_PRESS_MASK		(BIT(4) | BIT(3) | BIT(2))
#define BMP280_OSRS_PRESS_SKIP		0
#define BMP280_OSRS_PRESS_1X		BIT(2)
#define BMP280_OSRS_PRESS_2X		BIT(3)
#define BMP280_OSRS_PRESS_4X		(BIT(3) | BIT(2))
#define BMP280_OSRS_PRESS_8X		BIT(4)
#define BMP280_OSRS_PRESS_16X		(BIT(4) | BIT(2))

#define BMP280_MODE_MASK		(BIT(1) | BIT(0))
#define BMP280_MODE_SLEEP		0
#define BMP280_MODE_FORCED		BIT(0)
#define BMP280_MODE_NORMAL		(BIT(1) | BIT(0))

#define BMP280_CHIP_ID			0x58
#define BMP280_SOFT_RESET_VAL		0xB6

struct bmp280_data {
	struct i2c_client *client;
	struct mutex lock;
	struct regmap *regmap;

	/*
	 * Carryover value from temperature conversion, used in pressure
	 * calculation.
	 */
	s32 t_fine;
};

/*
 * These enums are used for indexing into the array of compensation
 * parameters.
 */
enum { T1, T2, T3 };
enum { P1, P2, P3, P4, P5, P6, P7, P8, P9 };

static const struct iio_chan_spec bmp280_channels[] = {
	{
		.type = IIO_PRESSURE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
	},
	{
		.type = IIO_TEMP,
		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
	},
};

static bool bmp280_is_writeable_reg(struct device *dev, unsigned int reg)
{
	switch (reg) {
	case BMP280_REG_CONFIG:
	case BMP280_REG_CTRL_MEAS:
	case BMP280_REG_RESET:
		return true;
	default:
		return false;
	};
}

static bool bmp280_is_volatile_reg(struct device *dev, unsigned int reg)
{
	switch (reg) {
	case BMP280_REG_TEMP_XLSB:
	case BMP280_REG_TEMP_LSB:
	case BMP280_REG_TEMP_MSB:
	case BMP280_REG_PRESS_XLSB:
	case BMP280_REG_PRESS_LSB:
	case BMP280_REG_PRESS_MSB:
	case BMP280_REG_STATUS:
		return true;
	default:
		return false;
	}
}

static const struct regmap_config bmp280_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,

	.max_register = BMP280_REG_TEMP_XLSB,
	.cache_type = REGCACHE_RBTREE,

	.writeable_reg = bmp280_is_writeable_reg,
	.volatile_reg = bmp280_is_volatile_reg,
};

/*
 * Returns temperature in DegC, resolution is 0.01 DegC.  Output value of
 * "5123" equals 51.23 DegC.  t_fine carries fine temperature as global
 * value.
 *
 * Taken from datasheet, Section 3.11.3, "Compensation formula".
 */
static s32 bmp280_compensate_temp(struct bmp280_data *data,
				  s32 adc_temp)
{
	int ret;
	s32 var1, var2, t;
	__le16 buf[BMP280_COMP_TEMP_REG_COUNT / 2];

	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
			       buf, BMP280_COMP_TEMP_REG_COUNT);
	if (ret < 0) {
		dev_err(&data->client->dev,
			"failed to read temperature calibration parameters\n");
		return ret;
	}

	/*
	 * The double casts are necessary because le16_to_cpu returns an
	 * unsigned 16-bit value.  Casting that value directly to a
	 * signed 32-bit will not do proper sign extension.
	 *
	 * Conversely, T1 and P1 are unsigned values, so they can be
	 * cast straight to the larger type.
	 */
	var1 = (((adc_temp >> 3) - ((s32)le16_to_cpu(buf[T1]) << 1)) *
		((s32)(s16)le16_to_cpu(buf[T2]))) >> 11;
	var2 = (((((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1]))) *
		  ((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1])))) >> 12) *
		((s32)(s16)le16_to_cpu(buf[T3]))) >> 14;

	data->t_fine = var1 + var2;
	t = (data->t_fine * 5 + 128) >> 8;

	return t;
}

/*
 * Returns pressure in Pa as unsigned 32 bit integer in Q24.8 format (24
 * integer bits and 8 fractional bits).  Output value of "24674867"
 * represents 24674867/256 = 96386.2 Pa = 963.862 hPa
 *
 * Taken from datasheet, Section 3.11.3, "Compensation formula".
 */
static u32 bmp280_compensate_press(struct bmp280_data *data,
				   s32 adc_press)
{
	int ret;
	s64 var1, var2, p;
	__le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];

	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,
			       buf, BMP280_COMP_PRESS_REG_COUNT);
	if (ret < 0) {
		dev_err(&data->client->dev,
			"failed to read pressure calibration parameters\n");
		return ret;
	}

	var1 = ((s64)data->t_fine) - 128000;
	var2 = var1 * var1 * (s64)(s16)le16_to_cpu(buf[P6]);
	var2 = var2 + ((var1 * (s64)(s16)le16_to_cpu(buf[P5])) << 17);
	var2 = var2 + (((s64)(s16)le16_to_cpu(buf[P4])) << 35);
	var1 = ((var1 * var1 * (s64)(s16)le16_to_cpu(buf[P3])) >> 8) +
		((var1 * (s64)(s16)le16_to_cpu(buf[P2])) << 12);
	var1 = ((((s64)1) << 47) + var1) * ((s64)le16_to_cpu(buf[P1])) >> 33;

	if (var1 == 0)
		return 0;

	p = ((((s64)1048576 - adc_press) << 31) - var2) * 3125;
	p = div64_s64(p, var1);
	var1 = (((s64)(s16)le16_to_cpu(buf[P9])) * (p >> 13) * (p >> 13)) >> 25;
	var2 = (((s64)(s16)le16_to_cpu(buf[P8])) * p) >> 19;
	p = ((p + var1 + var2) >> 8) + (((s64)(s16)le16_to_cpu(buf[P7])) << 4);

	return (u32) p;
}

static int bmp280_read_temp(struct bmp280_data *data,
			    int *val)
{
	int ret;
	__be32 tmp = 0;
	s32 adc_temp, comp_temp;

	ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
			       (u8 *) &tmp, 3);
	if (ret < 0) {
		dev_err(&data->client->dev, "failed to read temperature\n");
		return ret;
	}

	adc_temp = be32_to_cpu(tmp) >> 12;
	comp_temp = bmp280_compensate_temp(data, adc_temp);

	/*
	 * val might be NULL if we're called by the read_press routine,
	 * who only cares about the carry over t_fine value.
	 */
	if (val) {
		*val = comp_temp * 10;
		return IIO_VAL_INT;
	}

	return 0;
}

static int bmp280_read_press(struct bmp280_data *data,
			     int *val, int *val2)
{
	int ret;
	__be32 tmp = 0;
	s32 adc_press;
	u32 comp_press;

	/* Read and compensate temperature so we get a reading of t_fine. */
	ret = bmp280_read_temp(data, NULL);
	if (ret < 0)
		return ret;

	ret = regmap_bulk_read(data->regmap, BMP280_REG_PRESS_MSB,
			       (u8 *) &tmp, 3);
	if (ret < 0) {
		dev_err(&data->client->dev, "failed to read pressure\n");
		return ret;
	}

	adc_press = be32_to_cpu(tmp) >> 12;
	comp_press = bmp280_compensate_press(data, adc_press);

	*val = comp_press;
	*val2 = 256000;

	return IIO_VAL_FRACTIONAL;
}

static int bmp280_read_raw(struct iio_dev *indio_dev,
			   struct iio_chan_spec const *chan,
			   int *val, int *val2, long mask)
{
	int ret;
	struct bmp280_data *data = iio_priv(indio_dev);

	mutex_lock(&data->lock);

	switch (mask) {
	case IIO_CHAN_INFO_PROCESSED:
		switch (chan->type) {
		case IIO_PRESSURE:
			ret = bmp280_read_press(data, val, val2);
			break;
		case IIO_TEMP:
			ret = bmp280_read_temp(data, val);
			break;
		default:
			ret = -EINVAL;
			break;
		}
		break;
	default:
		ret = -EINVAL;
		break;
	}

	mutex_unlock(&data->lock);

	return ret;
}

static const struct iio_info bmp280_info = {
	.driver_module = THIS_MODULE,
	.read_raw = &bmp280_read_raw,
};

static int bmp280_chip_init(struct bmp280_data *data)
{
	int ret;

	ret = regmap_update_bits(data->regmap, BMP280_REG_CTRL_MEAS,
				 BMP280_OSRS_TEMP_MASK |
				 BMP280_OSRS_PRESS_MASK |
				 BMP280_MODE_MASK,
				 BMP280_OSRS_TEMP_2X |
				 BMP280_OSRS_PRESS_16X |
				 BMP280_MODE_NORMAL);
	if (ret < 0) {
		dev_err(&data->client->dev,
			"failed to write config register\n");
		return ret;
	}

	ret = regmap_update_bits(data->regmap, BMP280_REG_CONFIG,
				 BMP280_FILTER_MASK,
				 BMP280_FILTER_4X);
	if (ret < 0) {
		dev_err(&data->client->dev,
			"failed to write config register\n");
		return ret;
	}

	return ret;
}

static int bmp280_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	int ret;
	struct iio_dev *indio_dev;
	struct bmp280_data *data;
	unsigned int chip_id;

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
	if (!indio_dev)
		return -ENOMEM;

	i2c_set_clientdata(client, indio_dev);
	data = iio_priv(indio_dev);
	mutex_init(&data->lock);
	data->client = client;

	indio_dev->dev.parent = &client->dev;
	indio_dev->name = id->name;
	indio_dev->channels = bmp280_channels;
	indio_dev->num_channels = ARRAY_SIZE(bmp280_channels);
	indio_dev->info = &bmp280_info;
	indio_dev->modes = INDIO_DIRECT_MODE;

	data->regmap = devm_regmap_init_i2c(client, &bmp280_regmap_config);
	if (IS_ERR(data->regmap)) {
		dev_err(&client->dev, "failed to allocate register map\n");
		return PTR_ERR(data->regmap);
	}

	ret = regmap_read(data->regmap, BMP280_REG_ID, &chip_id);
	if (ret < 0)
		return ret;
	if (chip_id != BMP280_CHIP_ID) {
		dev_err(&client->dev, "bad chip id.  expected %x got %x\n",
			BMP280_CHIP_ID, chip_id);
		return -EINVAL;
	}

	ret = bmp280_chip_init(data);
	if (ret < 0)
		return ret;

	return devm_iio_device_register(&client->dev, indio_dev);
}

static const struct acpi_device_id bmp280_acpi_match[] = {
	{"BMP0280", 0},
	{ },
};
MODULE_DEVICE_TABLE(acpi, bmp280_acpi_match);

static const struct i2c_device_id bmp280_id[] = {
	{"bmp280", 0},
	{ },
};
MODULE_DEVICE_TABLE(i2c, bmp280_id);

static struct i2c_driver bmp280_driver = {
	.driver = {
		.name	= "bmp280",
		.acpi_match_table = ACPI_PTR(bmp280_acpi_match),
	},
	.probe		= bmp280_probe,
	.id_table	= bmp280_id,
};
module_i2c_driver(bmp280_driver);

MODULE_AUTHOR("Vlad Dogaru <vlad.dogaru@intel.com>");
MODULE_DESCRIPTION("Driver for Bosch Sensortec BMP280 pressure and temperature sensor");
MODULE_LICENSE("GPL v2");