iio: add bmp280 pressure and temperature driver

Minimal implementation, can read temperature and data using direct mode.

Datasheet available at
<http://ae-bst.resource.bosch.com/media/products/dokumente/bmp280/BST-BMP280-DS001-09.pdf>
Signed-off-by: Vlad Dogaru <vlad.dogaru@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/Kconfig

@@ -5,6 +5,17 @@
 
 menu "Pressure sensors"
 
+config BMP280
+	tristate "Bosch Sensortec BMP280 pressure sensor driver"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	 Say yes here to build support for Bosch Sensortec BMP280
+	 pressure and temperature sensor.
+
+	 To compile this driver as a module, choose M here: the module
+	 will be called bmp280.
+
 config HID_SENSOR_PRESS
 	depends on HID_SENSOR_HUB
 	select IIO_BUFFER

drivers/iio/pressure/Makefile

@@ -3,6 +3,7 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_BMP280) += bmp280.o
 obj-$(CONFIG_HID_SENSOR_PRESS)   += hid-sensor-press.o
 obj-$(CONFIG_MPL115) += mpl115.o
 obj-$(CONFIG_MPL3115) += mpl3115.o

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;
+};
+
+/* Compensation parameters. */
+struct bmp280_comp_temp {
+	u16 dig_t1;
+	s16 dig_t2, dig_t3;
+};
+
+struct bmp280_comp_press {
+	u16 dig_p1;
+	s16 dig_p2, dig_p3, dig_p4, dig_p5, dig_p6, dig_p7, dig_p8, dig_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,
+};
+
+static int bmp280_read_compensation_temp(struct bmp280_data *data,
+					 struct bmp280_comp_temp *comp)
+{
+	int ret;
+	__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;
+	}
+
+	comp->dig_t1 = (u16) le16_to_cpu(buf[0]);
+	comp->dig_t2 = (s16) le16_to_cpu(buf[1]);
+	comp->dig_t3 = (s16) le16_to_cpu(buf[2]);
+
+	return 0;
+}
+
+static int bmp280_read_compensation_press(struct bmp280_data *data,
+					  struct bmp280_comp_press *comp)
+{
+	int ret;
+	__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;
+	}
+
+	comp->dig_p1 = (s16) le16_to_cpu(buf[0]);
+	comp->dig_p2 = (u16) le16_to_cpu(buf[1]);
+	comp->dig_p3 = (u16) le16_to_cpu(buf[2]);
+	comp->dig_p4 = (u16) le16_to_cpu(buf[3]);
+	comp->dig_p5 = (u16) le16_to_cpu(buf[4]);
+	comp->dig_p6 = (u16) le16_to_cpu(buf[5]);
+	comp->dig_p7 = (u16) le16_to_cpu(buf[6]);
+	comp->dig_p8 = (u16) le16_to_cpu(buf[7]);
+	comp->dig_p9 = (u16) le16_to_cpu(buf[8]);
+
+	return 0;
+}
+
+/*
+ * 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,
+				  struct bmp280_comp_temp *comp,
+				  s32 adc_temp)
+{
+	s32 var1, var2, t;
+
+	var1 = (((adc_temp >> 3) - ((s32) comp->dig_t1 << 1)) *
+		((s32) comp->dig_t2)) >> 11;
+	var2 = (((((adc_temp >> 4) - ((s32) comp->dig_t1)) *
+		  ((adc_temp >> 4) - ((s32) comp->dig_t1))) >> 12) *
+		((s32) comp->dig_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,
+				   struct bmp280_comp_press *comp,
+				   s32 adc_press)
+{
+	s64 var1, var2, p;
+
+	var1 = ((s64) data->t_fine) - 128000;
+	var2 = var1 * var1 * (s64) comp->dig_p6;
+	var2 = var2 + ((var1 * (s64) comp->dig_p5) << 17);
+	var2 = var2 + (((s64) comp->dig_p4) << 35);
+	var1 = ((var1 * var1 * (s64) comp->dig_p3) >> 8) +
+		((var1 * (s64) comp->dig_p2) << 12);
+	var1 = (((((s64) 1) << 47) + var1)) * ((s64) comp->dig_p1) >> 33;
+
+	if (var1 == 0)
+		return 0;
+
+	p = ((((s64) 1048576 - adc_press) << 31) - var2) * 3125;
+	do_div(p, var1);
+	var1 = (((s64) comp->dig_p9) * (p >> 13) * (p >> 13)) >> 25;
+	var2 = (((s64) comp->dig_p8) * p) >> 19;
+	p = ((p + var1 + var2) >> 8) + (((s64) comp->dig_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;
+	struct bmp280_comp_temp comp;
+
+	ret = bmp280_read_compensation_temp(data, &comp);
+	if (ret < 0)
+		return ret;
+
+	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, &comp, 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;
+	struct bmp280_comp_press comp;
+
+	ret = bmp280_read_compensation_press(data, &comp);
+	if (ret < 0)
+		return ret;
+
+	/* 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, &comp, adc_press);
+
+	*val = comp_press / 256000;
+	*val2 = comp_press * 1000000 / 256000;
+
+	return IIO_VAL_INT_PLUS_MICRO;
+}
+
+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");