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From:   Dan Robertson <dan@dlrobertson.com>
To:     Jonathan Cameron <jic23@kernel.org>, linux-iio@vger.kernel.org
Cc:     Dan Robertson <dan@dlrobertson.com>, linux-kernel@vger.kernel.org
Message-ID: <20190925013941.20431-2-dan@dlrobertson.com>
Subject: [PATCH 1/1] iio: (bma400) add driver for the BMA400
Date:   Wed, 25 Sep 2019 01:39:41 +0000
In-Reply-To: <20190925013941.20431-1-dan@dlrobertson.com>
References: <20190925013941.20431-1-dan@dlrobertson.com>
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Add a IIO driver for the Bosch BMA400 3-axes ultra-low power accelerometer.
The driver supports reading from the acceleration and temperature
registers. The driver also supports reading and configuring the output data
rate, oversampling ratio, and scale.

Signed-off-by: Dan Robertson <dan@dlrobertson.com>
---
 drivers/iio/accel/Kconfig       |  19 +
 drivers/iio/accel/Makefile      |   2 +
 drivers/iio/accel/bma400.h      |  74 +++
 drivers/iio/accel/bma400_core.c | 862 ++++++++++++++++++++++++++++++++
 drivers/iio/accel/bma400_i2c.c  |  54 ++
 5 files changed, 1011 insertions(+)
 create mode 100644 drivers/iio/accel/bma400.h
 create mode 100644 drivers/iio/accel/bma400_core.c
 create mode 100644 drivers/iio/accel/bma400_i2c.c

diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
index 9b9656ce37e6..cca6727e037e 100644
--- a/drivers/iio/accel/Kconfig
+++ b/drivers/iio/accel/Kconfig
@@ -112,6 +112,25 @@ config BMA220
 	  To compile this driver as a module, choose M here: the
 	  module will be called bma220_spi.
 
+config BMA400
+	tristate "Bosch BMA400 3-Axis Accelerometer Driver"
+	depends on I2C
+	select REGMAP
+	select BMA400_I2C if (I2C)
+	help
+	  Say Y here if you want to build a driver for the Bosch BMA400
+	  triaxial acceleration sensor.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called bma400_core and you will also get
+	  bma400_i2c for I2C
+
+config BMA400_I2C
+	tristate
+	depends on BMA400
+	depends on I2C
+	select REGMAP_I2C
+
 config BMC150_ACCEL
 	tristate "Bosch BMC150 Accelerometer Driver"
 	select IIO_BUFFER
diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
index 56bd0215e0d4..3a051cf37f40 100644
--- a/drivers/iio/accel/Makefile
+++ b/drivers/iio/accel/Makefile
@@ -14,6 +14,8 @@ obj-$(CONFIG_ADXL372_I2C) += adxl372_i2c.o
 obj-$(CONFIG_ADXL372_SPI) += adxl372_spi.o
 obj-$(CONFIG_BMA180) += bma180.o
 obj-$(CONFIG_BMA220) += bma220_spi.o
+obj-$(CONFIG_BMA400) += bma400_core.o
+obj-$(CONFIG_BMA400_I2C) += bma400_i2c.o
 obj-$(CONFIG_BMC150_ACCEL) += bmc150-accel-core.o
 obj-$(CONFIG_BMC150_ACCEL_I2C) += bmc150-accel-i2c.o
 obj-$(CONFIG_BMC150_ACCEL_SPI) += bmc150-accel-spi.o
diff --git a/drivers/iio/accel/bma400.h b/drivers/iio/accel/bma400.h
new file mode 100644
index 000000000000..7fa92bc457f6
--- /dev/null
+++ b/drivers/iio/accel/bma400.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * bma400.h - Register constants and other forward declarations
+ *            needed by the bma400 sources.
+ *
+ * Copyright 2019 Dan Robertson <dan@dlrobertson.com>
+ *
+ */
+
+#include <linux/regmap.h>
+
+/*
+ * Read-Only Registers
+ */
+
+/* Status and ID registers */
+#define BMA400_CHIP_ID_REG      0x00
+#define BMA400_ERR_REG          0x02
+#define BMA400_STATUS_REG       0x03
+
+/* Acceleration registers */
+#define BMA400_X_AXIS_LSB_REG   0x04
+#define BMA400_X_AXIS_MSB_REG   0x05
+#define BMA400_Y_AXIS_LSB_REG   0x06
+#define BMA400_Y_AXIS_MSB_REG   0x07
+#define BMA400_Z_AXIS_LSB_REG   0x08
+#define BMA400_Z_AXIS_MSB_REG   0x09
+
+/* Sensort time registers */
+#define BMA400_SENSOR_TIME0     0x0a
+#define BMA400_SENSOR_TIME1     0x0b
+#define BMA400_SENSOR_TIME2     0x0c
+
+/* Event and interrupt registers */
+#define BMA400_EVENT_REG        0x0d
+#define BMA400_INT_STAT0_REG    0x0e
+#define BMA400_INT_STAT1_REG    0x0f
+#define BMA400_INT_STAT2_REG    0x10
+
+/* Temperature register */
+#define BMA400_TEMP_DATA_REG    0x11
+
+/* FIFO length and data registers */
+#define BMA400_FIFO_LENGTH0_REG 0x12
+#define BMA400_FIFO_LENGTH1_REG 0x13
+#define BMA400_FIFO_DATA_REG    0x14
+
+/* Step count registers */
+#define BMA400_STEP_CNT0_REG    0x15
+#define BMA400_STEP_CNT1_REG    0x16
+#define BMA400_STEP_CNT3_REG    0x17
+#define BMA400_STEP_STAT_REG    0x18
+
+/*
+ * Read-write configuration registers
+ */
+#define BMA400_ACC_CONFIG0_REG  0x19
+#define BMA400_ACC_CONFIG1_REG  0x1a
+#define BMA400_ACC_CONFIG2_REG  0x1b
+#define BMA400_CMD_REG          0x7e
+
+/* Chip ID of BMA 400 devices found in the chip ID register. */
+#define BMA400_ID_REG_VAL       0x90
+
+/* The softreset command */
+#define BMA400_SOFTRESET_CMD    0xb6
+
+extern const struct regmap_config bma400_regmap_config;
+
+int bma400_probe(struct device *dev,
+		 struct regmap *regmap,
+		 const char *name);
+
+int bma400_remove(struct device *dev);
diff --git a/drivers/iio/accel/bma400_core.c b/drivers/iio/accel/bma400_core.c
new file mode 100644
index 000000000000..55fe2f220c30
--- /dev/null
+++ b/drivers/iio/accel/bma400_core.c
@@ -0,0 +1,862 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * bma400-core.c - Core IIO driver for Bosch BMA400 triaxial acceleration
+ *                 sensor. Used by bma400-i2c.
+ *
+ * Copyright 2019 Dan Robertson <dan@dlrobertson.com>
+ *
+ * TODO:
+ *  - Support for power management
+ *  - Support events and interrupts
+ *  - Create channel the step count
+ *  - Create channel for sensor time
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/bitops.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#include "bma400.h"
+
+/*
+ * The G-range selection may be one of 2g, 4g, 8, or 16g. The scale may
+ * be selected with the acc_range bits of the ACC_CONFIG1 register.
+ */
+const int bma400_scale_table[] = { 38344, 76590, 153277, 306457 };
+
+struct bma400_sample_freq {
+	int hz;
+	int micro_hz;
+};
+
+/* See the ACC_CONFIG1 section of the datasheet */
+const struct bma400_sample_freq bma400_sample_freqs[] = {
+	{ .hz = 12, .micro_hz = 500000 },
+	{ .hz = 25, .micro_hz = 0 },
+	{ .hz = 50, .micro_hz = 0 },
+	{ .hz = 100, .micro_hz = 0 },
+	{ .hz = 200, .micro_hz = 0 },
+	{ .hz = 400, .micro_hz = 0 },
+	{ .hz = 800, .micro_hz = 0 },
+};
+
+/* See the ACC_CONFIG0 section of the datasheet */
+enum bma400_power_mode {
+	POWER_MODE_SLEEP   = 0x00,
+	POWER_MODE_LOW     = 0x01,
+	POWER_MODE_NORMAL  = 0x02,
+	POWER_MODE_INVALID = 0x03,
+};
+
+struct bma400_data {
+	struct device *dev;
+	struct mutex mutex; /* data register lock */
+	struct iio_mount_matrix orientation;
+	struct regmap *regmap;
+	enum bma400_power_mode power_mode;
+	const struct bma400_sample_freq *sample_freq;
+	int oversampling_ratio;
+	int scale;
+};
+
+static bool bma400_is_writable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case BMA400_CHIP_ID_REG:
+	case BMA400_ERR_REG:
+	case BMA400_STATUS_REG:
+	case BMA400_X_AXIS_LSB_REG:
+	case BMA400_X_AXIS_MSB_REG:
+	case BMA400_Y_AXIS_LSB_REG:
+	case BMA400_Y_AXIS_MSB_REG:
+	case BMA400_Z_AXIS_LSB_REG:
+	case BMA400_Z_AXIS_MSB_REG:
+	case BMA400_SENSOR_TIME0:
+	case BMA400_SENSOR_TIME1:
+	case BMA400_SENSOR_TIME2:
+	case BMA400_EVENT_REG:
+	case BMA400_INT_STAT0_REG:
+	case BMA400_INT_STAT1_REG:
+	case BMA400_INT_STAT2_REG:
+	case BMA400_TEMP_DATA_REG:
+	case BMA400_FIFO_LENGTH0_REG:
+	case BMA400_FIFO_LENGTH1_REG:
+	case BMA400_FIFO_DATA_REG:
+	case BMA400_STEP_CNT0_REG:
+	case BMA400_STEP_CNT1_REG:
+	case BMA400_STEP_CNT3_REG:
+	case BMA400_STEP_STAT_REG:
+		return false;
+	default:
+		return true;
+	}
+}
+
+static bool bma400_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case BMA400_ERR_REG:
+	case BMA400_STATUS_REG:
+	case BMA400_X_AXIS_LSB_REG:
+	case BMA400_X_AXIS_MSB_REG:
+	case BMA400_Y_AXIS_LSB_REG:
+	case BMA400_Y_AXIS_MSB_REG:
+	case BMA400_Z_AXIS_LSB_REG:
+	case BMA400_Z_AXIS_MSB_REG:
+	case BMA400_SENSOR_TIME0:
+	case BMA400_SENSOR_TIME1:
+	case BMA400_SENSOR_TIME2:
+	case BMA400_EVENT_REG:
+	case BMA400_INT_STAT0_REG:
+	case BMA400_INT_STAT1_REG:
+	case BMA400_INT_STAT2_REG:
+	case BMA400_TEMP_DATA_REG:
+	case BMA400_FIFO_LENGTH0_REG:
+	case BMA400_FIFO_LENGTH1_REG:
+	case BMA400_FIFO_DATA_REG:
+	case BMA400_STEP_CNT0_REG:
+	case BMA400_STEP_CNT1_REG:
+	case BMA400_STEP_CNT3_REG:
+	case BMA400_STEP_STAT_REG:
+		return true;
+	default:
+		return false;
+	}
+}
+
+const struct regmap_config bma400_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = BMA400_CMD_REG,
+	.cache_type = REGCACHE_RBTREE,
+	.writeable_reg = bma400_is_writable_reg,
+	.volatile_reg = bma400_is_volatile_reg,
+};
+EXPORT_SYMBOL(bma400_regmap_config);
+
+static const struct iio_mount_matrix *
+bma400_accel_get_mount_matrix(const struct iio_dev *indio_dev,
+			      const struct iio_chan_spec *chan)
+{
+	struct bma400_data *data = iio_priv(indio_dev);
+
+	return &data->orientation;
+}
+
+static const struct iio_chan_spec_ext_info bma400_ext_info[] = {
+	IIO_MOUNT_MATRIX(IIO_SHARED_BY_DIR, bma400_accel_get_mount_matrix),
+	{ }
+};
+
+#define BMA400_ACC_CHANNEL(_axis) { \
+	.type = IIO_ACCEL, \
+	.modified = 1, \
+	.channel2 = IIO_MOD_##_axis, \
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \
+		BIT(IIO_CHAN_INFO_SCALE) | \
+		BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
+	.ext_info = bma400_ext_info \
+}
+
+static const struct iio_chan_spec bma400_channels[] = {
+	BMA400_ACC_CHANNEL(X),
+	BMA400_ACC_CHANNEL(Y),
+	BMA400_ACC_CHANNEL(Z),
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+	},
+};
+
+static int bma400_get_temp_reg(struct bma400_data *data, int *val, int *val2)
+{
+	int ret;
+	int host_temp;
+	unsigned int raw_temp;
+
+	if (data->power_mode == POWER_MODE_SLEEP)
+		return -EBUSY;
+
+	ret = regmap_read(data->regmap, BMA400_TEMP_DATA_REG, &raw_temp);
+
+	if (!ret) {
+		host_temp = sign_extend32(raw_temp, 7);
+		/*
+		 * The formula for the TEMP_DATA register in the datasheet
+		 * is: x * 0.5 + 23
+		 */
+		*val = (host_temp >> 1) + 23;
+		*val2 = (host_temp & 0x1) * 500000;
+		ret = IIO_VAL_INT_PLUS_MICRO;
+	}
+	return ret;
+}
+
+static int bma400_get_accel_reg(struct bma400_data *data,
+				const struct iio_chan_spec *chan,
+				int *val)
+{
+	int ret;
+	u16 lsb_reg;
+	__le16 raw_accel = 0;
+
+	if (data->power_mode == POWER_MODE_SLEEP)
+		return -EBUSY;
+
+	switch (chan->channel2) {
+	case IIO_MOD_X:
+		lsb_reg = BMA400_X_AXIS_LSB_REG;
+		break;
+	case IIO_MOD_Y:
+		lsb_reg = BMA400_Y_AXIS_LSB_REG;
+		break;
+	case IIO_MOD_Z:
+		lsb_reg = BMA400_Z_AXIS_LSB_REG;
+		break;
+	default:
+		dev_err(data->dev, "invalid axis channel modifier");
+		return -EINVAL;
+	}
+
+	/* bulk read two registers, with the base being the LSB register */
+	ret = regmap_bulk_read(data->regmap, lsb_reg, &raw_accel, 2);
+	if (!ret) {
+		*val = sign_extend32(le16_to_cpu(raw_accel), 11);
+		ret = IIO_VAL_INT;
+	}
+
+	return ret;
+}
+
+static int bma400_ready_for_cmd(struct bma400_data *data)
+{
+	unsigned int val;
+	int ret = regmap_read(data->regmap, BMA400_STATUS_REG, &val);
+
+	if (ret < 0 || !(val & 0x10))
+		return 0;
+
+	return 1;
+}
+
+static int bma400_softreset(struct bma400_data *data)
+{
+	int ret;
+
+	if (!bma400_ready_for_cmd(data))
+		return -EAGAIN;
+
+	ret = regmap_write(data->regmap, BMA400_CMD_REG,
+			   BMA400_SOFTRESET_CMD);
+	if (!ret) {
+		/* a softreset restores registers to their defaults */
+		data->power_mode = POWER_MODE_SLEEP;
+		data->sample_freq = NULL;
+		data->oversampling_ratio = -1;
+		data->scale = bma400_scale_table[0];
+	}
+	return ret;
+}
+
+static int bma400_get_acc_config0_reg(struct bma400_data *data)
+{
+	int ret;
+	unsigned int val;
+
+	ret = regmap_read(data->regmap, BMA400_ACC_CONFIG0_REG,
+			  &val);
+	if (ret < 0) {
+		dev_err(data->dev, "Failed read acc_config0");
+		return ret;
+	}
+
+	return val;
+}
+
+static int bma400_get_acc_config1_reg(struct bma400_data *data)
+{
+	int ret;
+	unsigned int val;
+
+	ret = regmap_read(data->regmap, BMA400_ACC_CONFIG1_REG,
+			  &val);
+	if (ret < 0) {
+		dev_err(data->dev, "Failed read acc_config1");
+		return ret;
+	}
+
+	return val;
+}
+
+static int bma400_get_accel_output_data_rate(struct bma400_data *data)
+{
+	int acc_config1;
+	unsigned int odr;
+	int idx;
+
+	switch (data->power_mode) {
+	case POWER_MODE_LOW:
+		/*
+		 * Runs at a fixed rate in low-power mode. See section 4.3
+		 * in the datasheet.
+		 */
+		data->sample_freq = &bma400_sample_freqs[1];
+		return 0;
+	case POWER_MODE_NORMAL:
+		/*
+		 * In normal mode the ODR can be found in the ACC_CONFIG1
+		 * register.
+		 */
+		acc_config1 = bma400_get_acc_config1_reg(data);
+		if (acc_config1 < 0) {
+			data->sample_freq = NULL;
+			return acc_config1;
+		}
+
+		odr = (acc_config1 & 0x0f);
+		if (odr < 0x05 || odr > 0x0b) {
+			dev_err(data->dev, "invalid ODR=%x", odr);
+			data->sample_freq = NULL;
+			return -EINVAL;
+		}
+		idx = odr - 0x05;
+
+		data->sample_freq = &bma400_sample_freqs[idx];
+		return 0;
+	default:
+		data->sample_freq = NULL;
+		return 0;
+	}
+}
+
+static int bma400_get_accel_output_data_rate_idx(struct bma400_data *data,
+						 int hz, int uhz)
+{
+	int i;
+	const struct bma400_sample_freq *sample_freq;
+
+	for (i = 0; i < ARRAY_SIZE(bma400_sample_freqs); ++i) {
+		sample_freq = &bma400_sample_freqs[i];
+		if (sample_freq->hz == hz &&
+		    sample_freq->micro_hz == uhz)
+			return i;
+	}
+
+	return -EINVAL;
+}
+
+static int bma400_set_accel_output_data_rate(struct bma400_data *data,
+					     int hz, int uhz)
+{
+	int acc_config1;
+	unsigned int odr;
+	int idx;
+	int ret;
+
+	idx = bma400_get_accel_output_data_rate_idx(data, hz, uhz);
+
+	if (idx < 0)
+		return idx;
+
+	acc_config1 = bma400_get_acc_config1_reg(data);
+
+	if (acc_config1 < 0)
+		return acc_config1;
+
+	/* preserve the range and normal mode osr */
+	odr = (0xf0 & acc_config1) | (idx + 0x5);
+
+	ret = regmap_write(data->regmap, BMA400_ACC_CONFIG1_REG, odr);
+	if (!ret)
+		data->sample_freq = &bma400_sample_freqs[idx];
+
+	return ret;
+}
+
+static int bma400_get_accel_oversampling_ratio(struct bma400_data *data)
+{
+	int acc_config;
+
+	/*
+	 * The oversampling ratio is stored in a different register
+	 * based on the power-mode. In normal mode the OSR is stored
+	 * in ACC_CONFIG1. In low-power mode it is stored in
+	 * ACC_CONFIG0.
+	 */
+	switch (data->power_mode) {
+	case POWER_MODE_LOW:
+		acc_config = bma400_get_acc_config0_reg(data);
+		if (acc_config < 0) {
+			data->oversampling_ratio = -1;
+			return acc_config;
+		}
+
+		data->oversampling_ratio = (acc_config & 0x60) >> 5;
+		return 0;
+	case POWER_MODE_NORMAL:
+		acc_config = bma400_get_acc_config1_reg(data);
+		if (acc_config < 0) {
+			data->oversampling_ratio = -1;
+			return acc_config;
+		}
+
+		data->oversampling_ratio = (acc_config & 0x30) >> 4;
+		return 0;
+	default:
+		data->oversampling_ratio = -1;
+		return 0;
+	}
+}
+
+static int bma400_set_accel_oversampling_ratio(struct bma400_data *data,
+					       int val)
+{
+	int ret;
+	int acc_config;
+
+	/* The oversampling ratio is a two bit field */
+	if (val & ~0x3)
+		return -EINVAL;
+
+	/* The oversampling ratio is stored in a different register
+	 * based on the power-mode.
+	 */
+	switch (data->power_mode) {
+	case POWER_MODE_LOW:
+		acc_config = bma400_get_acc_config0_reg(data);
+		if (acc_config < 0)
+			return acc_config;
+
+		ret = regmap_write(data->regmap, BMA400_ACC_CONFIG0_REG,
+				   (acc_config & 0x9f) | (val << 5));
+		if (ret < 0)
+			dev_err(data->dev, "Failed to write out OSR");
+		else
+			data->oversampling_ratio = val;
+		break;
+	case POWER_MODE_NORMAL:
+		acc_config = bma400_get_acc_config1_reg(data);
+		if (acc_config < 0)
+			return acc_config;
+
+		ret = regmap_write(data->regmap, BMA400_ACC_CONFIG1_REG,
+				   (acc_config & 0xcf) | (val << 4));
+		if (ret < 0)
+			dev_err(data->dev, "Failed to write out OSR");
+		else
+			data->oversampling_ratio = val;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return ret;
+}
+
+static int bma400_get_accel_scale(struct bma400_data *data)
+{
+	int idx;
+	int acc_config1 = bma400_get_acc_config1_reg(data);
+
+	if (acc_config1 < 0)
+		return acc_config1;
+
+	idx = (acc_config1 & 0xc0) >> 6;
+	if (idx < ARRAY_SIZE(bma400_scale_table)) {
+		data->scale = bma400_scale_table[idx];
+		return 0;
+	}
+	return -EINVAL;
+}
+
+static int bma400_get_accel_scale_idx(struct bma400_data *data, int val)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(bma400_scale_table); ++i) {
+		if (bma400_scale_table[i] == val)
+			return i;
+	}
+	return -EINVAL;
+}
+
+static int bma400_set_accel_scale(struct bma400_data *data, unsigned int val)
+{
+	int ret;
+	int idx;
+	int acc_config1 = bma400_get_acc_config1_reg(data);
+
+	if (acc_config1 < 0)
+		return acc_config1;
+
+	idx = bma400_get_accel_scale_idx(data, val);
+
+	if (idx < 0)
+		return idx;
+
+	ret = regmap_write(data->regmap, BMA400_ACC_CONFIG1_REG,
+			   (acc_config1 & 0x3f) | (idx << 6));
+	if (ret < 0)
+		return ret;
+
+	data->scale = val;
+	return 0;
+}
+
+static int bma400_get_power_mode(struct bma400_data *data)
+{
+	int ret;
+	unsigned int val;
+
+	ret = regmap_read(data->regmap, BMA400_STATUS_REG, &val);
+	if (ret < 0) {
+		dev_err(data->dev, "Failed to read status register");
+		return ret;
+	}
+
+	data->power_mode = (val >> 1) & 0x03;
+	return 0;
+}
+
+static int bma400_set_power_mode(struct bma400_data *data,
+				 enum bma400_power_mode mode)
+{
+	int ret;
+
+	ret = bma400_get_acc_config0_reg(data);
+
+	if (ret < 0)
+		return ret;
+
+	if (data->power_mode == mode)
+		return 0;
+
+	if (mode == POWER_MODE_INVALID)
+		return -EINVAL;
+
+	/* Preserve the low-power oversample ratio etc */
+	ret = regmap_write(data->regmap, BMA400_ACC_CONFIG0_REG,
+			   mode | (ret & 0xfc));
+
+	if (ret < 0) {
+		dev_err(data->dev, "Failed to write to power-mode");
+		return ret;
+	}
+
+	/* Update our cached power-mode */
+	data->power_mode = mode;
+
+	/*
+	 * Update our cached osr and odr based on the new
+	 * power-mode.
+	 */
+	bma400_get_accel_output_data_rate(data);
+	bma400_get_accel_oversampling_ratio(data);
+
+	return 0;
+}
+
+static int bma400_init(struct bma400_data *data)
+{
+	int ret;
+	unsigned int val;
+
+	/* Try to read chip_id register. It must return 0x90. */
+	ret = regmap_read(data->regmap, BMA400_CHIP_ID_REG, &val);
+
+	if (ret < 0) {
+		dev_err(data->dev, "Failed to read chip id register: %x!", ret);
+		return ret;
+	} else if (val != BMA400_ID_REG_VAL) {
+		dev_err(data->dev, "CHIP ID MISMATCH: %x!", ret);
+		return -ENODEV;
+	}
+
+	ret = bma400_get_power_mode(data);
+	if (ret < 0) {
+		dev_err(data->dev, "Failed to get the initial power-mode!");
+		return ret;
+	}
+
+	if (data->power_mode != POWER_MODE_NORMAL) {
+		ret = bma400_set_power_mode(data, POWER_MODE_NORMAL);
+		if (ret < 0) {
+			dev_err(data->dev, "Failed to wake up the device!");
+			return ret;
+		}
+		/*
+		 * TODO: The datasheet waits 1500us here in the example, but
+		 * lists 2/ODR as the wakeup time.
+		 */
+		usleep_range(1500, 20000);
+	}
+
+	ret = bma400_get_accel_output_data_rate(data);
+	if (ret < 0)
+		return ret;
+
+	ret = bma400_get_accel_oversampling_ratio(data);
+	if (ret < 0)
+		return ret;
+
+	ret = bma400_get_accel_scale(data);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Once the interrupt engine is supported we might use the
+	 * data_src_reg, but for now ensure this is set to the
+	 * variable ODR filter selectable by the sample frequency
+	 * channel.
+	 */
+	return regmap_write(data->regmap, BMA400_ACC_CONFIG2_REG, 0x00);
+}
+
+static ssize_t bma400_show_samp_freq_avail(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	int i;
+	int len = 0;
+	const struct bma400_sample_freq *sample_freq;
+
+	for (i = 0; i < ARRAY_SIZE(bma400_sample_freqs); ++i) {
+		sample_freq = &bma400_sample_freqs[i];
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%d.%06d ",
+				 sample_freq->hz, sample_freq->micro_hz);
+	}
+
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static ssize_t bma400_show_scale_avail(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	int i;
+	int len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(bma400_scale_table); ++i)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "0.%06d ",
+				 bma400_scale_table[i]);
+
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(bma400_show_samp_freq_avail);
+
+static IIO_DEVICE_ATTR(in_accel_scale_available, 0444,
+		       bma400_show_scale_avail, NULL, 0);
+
+static struct attribute *bma400_attributes[] = {
+	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
+	&iio_dev_attr_in_accel_scale_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group bma400_attrs_group = {
+	.attrs = bma400_attributes,
+};
+
+static int bma400_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan, int *val,
+			   int *val2, long mask)
+{
+	struct bma400_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		mutex_lock(&data->mutex);
+		ret = bma400_get_temp_reg(data, val, val2);
+		mutex_unlock(&data->mutex);
+		return ret;
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&data->mutex);
+		ret = bma400_get_accel_reg(data, chan, val);
+		mutex_unlock(&data->mutex);
+		return ret;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		switch (chan->type) {
+		case IIO_ACCEL:
+			if (!data->sample_freq)
+				return -EINVAL;
+
+			*val = data->sample_freq->hz;
+			if (!data->sample_freq->micro_hz)
+				return IIO_VAL_INT;
+
+			*val2 = data->sample_freq->micro_hz;
+			return IIO_VAL_INT_PLUS_MICRO;
+		case IIO_TEMP:
+			/*
+			 * Runs at a fixed sampling frequency. See Section 4.4
+			 * of the datasheet.
+			 */
+			*val = 6;
+			*val2 = 250000;
+			return IIO_VAL_INT_PLUS_MICRO;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = data->scale;
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		/*
+		 * TODO: We could avoid this logic and returning -EINVAL here if
+		 * we set both the low-power and normal mode OSR registers when
+		 * we configure the device.
+		 */
+		if (data->oversampling_ratio < 0)
+			return -EINVAL;
+
+		*val = data->oversampling_ratio;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int bma400_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int val, int val2,
+			    long mask)
+{
+	int ret;
+	struct bma400_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		/*
+		 * The sample frequency is readonly for the temperature
+		 * register and a fixed value in low-power mode.
+		 */
+		if (chan->type != IIO_ACCEL)
+			return -EINVAL;
+
+		mutex_lock(&data->mutex);
+		ret = bma400_set_accel_output_data_rate(data, val, val2);
+		mutex_unlock(&data->mutex);
+		return ret;
+	case IIO_CHAN_INFO_SCALE:
+		if (val != 0)
+			return -EINVAL;
+
+		mutex_lock(&data->mutex);
+		ret = bma400_set_accel_scale(data, val2);
+		mutex_unlock(&data->mutex);
+		return ret;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		mutex_lock(&data->mutex);
+		ret = bma400_set_accel_oversampling_ratio(data, val);
+		mutex_unlock(&data->mutex);
+		return ret;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int bma400_write_raw_get_fmt(struct iio_dev *indio_dev,
+				    struct iio_chan_spec const *chan,
+				    long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_SCALE:
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info bma400_info = {
+	.attrs             = &bma400_attrs_group,
+	.read_raw          = bma400_read_raw,
+	.write_raw         = bma400_write_raw,
+	.write_raw_get_fmt = bma400_write_raw_get_fmt,
+};
+
+int bma400_probe(struct device *dev,
+		 struct regmap *regmap,
+		 const char *name)
+{
+	int ret;
+	struct bma400_data *data;
+	struct iio_dev *indio_dev;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->regmap = regmap;
+	data->dev = dev;
+
+	ret = bma400_init(data);
+	if (ret < 0)
+		return ret;
+
+	ret = iio_read_mount_matrix(dev, "mount-matrix",
+				    &data->orientation);
+	if (ret)
+		return ret;
+
+	mutex_init(&data->mutex);
+	indio_dev->dev.parent = dev;
+	indio_dev->name = name;
+	indio_dev->info = &bma400_info;
+	indio_dev->channels = bma400_channels;
+	indio_dev->num_channels = ARRAY_SIZE(bma400_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	dev_set_drvdata(dev, indio_dev);
+
+	ret = iio_device_register(indio_dev);
+	if (ret < 0) {
+		dev_err(dev, "unable to register iio device\n");
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(bma400_probe);
+
+int bma400_remove(struct device *dev)
+{
+	int ret;
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct bma400_data *data = iio_priv(indio_dev);
+
+	mutex_lock(&data->mutex);
+	ret = bma400_softreset(data);
+	if (ret < 0) {
+		/*
+		 * If the softreset failed, try to put the device in
+		 * sleep mode, but still report the error.
+		 */
+		dev_err(data->dev, "Failed to reset the device");
+		bma400_set_power_mode(data, POWER_MODE_SLEEP);
+	}
+	mutex_unlock(&data->mutex);
+
+	iio_device_unregister(indio_dev);
+
+	return ret;
+}
+EXPORT_SYMBOL(bma400_remove);
+
+MODULE_AUTHOR("Dan Robertson <dan@dlrobertson.com>");
+MODULE_DESCRIPTION("Bosch BMA400 triaxial acceleration sensor");
+MODULE_LICENSE("GPL");
diff --git a/drivers/iio/accel/bma400_i2c.c b/drivers/iio/accel/bma400_i2c.c
new file mode 100644
index 000000000000..227012a32e13
--- /dev/null
+++ b/drivers/iio/accel/bma400_i2c.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * bma400-i2c.c - I2C IIO driver for Bosch BMA400 triaxial acceleration sensor.
+ *
+ * Copyright 2019 Dan Robertson <dan@dlrobertson.com>
+ *
+ * I2C address is either 0x14 or 0x15 depending on SDO
+ *
+ */
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/acpi.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#include "bma400.h"
+
+static int bma400_i2c_probe(struct i2c_client *client,
+			    const struct i2c_device_id *id)
+{
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init_i2c(client,
+				      &bma400_regmap_config);
+
+	return bma400_probe(&client->dev, regmap, id->name);
+}
+
+static int bma400_i2c_remove(struct i2c_client *client)
+{
+	return bma400_remove(&client->dev);
+}
+
+static const struct i2c_device_id bma400_i2c_ids[] = {
+	{ "bma400", 0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, bma400_i2c_ids);
+
+static struct i2c_driver bma400_i2c_driver = {
+	.driver = {
+		.name = "bma400",
+	},
+	.probe    = bma400_i2c_probe,
+	.remove   = bma400_i2c_remove,
+	.id_table = bma400_i2c_ids,
+};
+
+module_i2c_driver(bma400_i2c_driver);
+
+MODULE_AUTHOR("Dan Robertson <dan@dlrobertson.com>");
+MODULE_DESCRIPTION("Bosch BMA400 triaxial acceleration sensor");
+MODULE_LICENSE("GPL");