iio: (bma400) add driver for the BMA400

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

@@ -112,6 +112,24 @@ 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
+	select REGMAP_I2C
+
 config BMC150_ACCEL
 	tristate "Bosch BMC150 Accelerometer Driver"
 	select IIO_BUFFER

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

drivers/iio/accel/bma400.h

@@ -0,0 +1,80 @@
+/* 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
+
+/* Sensor 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
+
+#define BMA400_TWO_BITS_MASK    0x03
+#define BMA400_LP_OSR_MASK      0x60
+#define BMA400_NP_OSR_MASK      0x30
+#define BMA400_ACC_ODR_MASK     0x0f
+#define BMA400_ACC_SCALE_MASK   0xc0
+
+#define BMA400_LP_OSR_SHIFT     0x05
+#define BMA400_NP_OSR_SHIFT     0x04
+#define BMA400_SCALE_SHIFT      0x06
+
+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);