iio: accel: Add support for the Bosch-Sensortec BMI088

The BMI088 is a combined module with both accelerometer and gyroscope.
This adds the accelerometer driver support for the SPI interface.
The gyroscope part is already supported by the BMG160 driver.
Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20210125150732.23873-2-mike.looijmans@topic.nlSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/Kconfig

@@ -157,6 +157,24 @@ config BMC150_ACCEL_SPI
 	tristate
 	select REGMAP_SPI
 
+config BMI088_ACCEL
+	tristate "Bosch BMI088 Accelerometer Driver"
+	depends on SPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	select REGMAP
+	select BMI088_ACCEL_SPI
+	help
+	  Say yes here to build support for the Bosch BMI088 accelerometer.
+
+	  This is a combo module with both accelerometer and gyroscope. This
+	  driver only implements the accelerometer part, which has its own
+	  address and register map. BMG160 provides the gyroscope driver.
+
+config BMI088_ACCEL_SPI
+	tristate
+	select REGMAP_SPI
+
 config DA280
 	tristate "MiraMEMS DA280 3-axis 14-bit digital accelerometer driver"
 	depends on I2C

drivers/iio/accel/Makefile

@@ -20,6 +20,8 @@ obj-$(CONFIG_BMA400_SPI) += bma400_spi.o
 obj-$(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
+obj-$(CONFIG_BMI088_ACCEL) += bmi088-accel-core.o
+obj-$(CONFIG_BMI088_ACCEL_SPI) += bmi088-accel-spi.o
 obj-$(CONFIG_DA280)	+= da280.o
 obj-$(CONFIG_DA311)	+= da311.o
 obj-$(CONFIG_DMARD06)	+= dmard06.o

drivers/iio/accel/bmi088-accel-spi.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 3-axis accelerometer driver supporting following Bosch-Sensortec chips:
+ *  - BMI088
+ *
+ * Copyright (c) 2018-2020, Topic Embedded Products
+ */
+
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+
+#include "bmi088-accel.h"
+
+static int bmi088_regmap_spi_write(void *context, const void *data, size_t count)
+{
+	struct spi_device *spi = context;
+
+	/* Write register is same as generic SPI */
+	return spi_write(spi, data, count);
+}
+
+static int bmi088_regmap_spi_read(void *context, const void *reg,
+				size_t reg_size, void *val, size_t val_size)
+{
+	struct spi_device *spi = context;
+	u8 addr[2];
+
+	addr[0] = *(u8 *)reg;
+	addr[0] |= BIT(7); /* Set RW = '1' */
+	addr[1] = 0; /* Read requires a dummy byte transfer */
+
+	return spi_write_then_read(spi, addr, sizeof(addr), val, val_size);
+}
+
+static struct regmap_bus bmi088_regmap_bus = {
+	.write = bmi088_regmap_spi_write,
+	.read = bmi088_regmap_spi_read,
+};
+
+static int bmi088_accel_probe(struct spi_device *spi)
+{
+	struct regmap *regmap;
+	const struct spi_device_id *id = spi_get_device_id(spi);
+
+	regmap = devm_regmap_init(&spi->dev, &bmi088_regmap_bus,
+			spi, &bmi088_regmap_conf);
+
+	if (IS_ERR(regmap)) {
+		dev_err(&spi->dev, "Failed to initialize spi regmap\n");
+		return PTR_ERR(regmap);
+	}
+
+	return bmi088_accel_core_probe(&spi->dev, regmap, spi->irq, id->name,
+				       true);
+}
+
+static int bmi088_accel_remove(struct spi_device *spi)
+{
+	return bmi088_accel_core_remove(&spi->dev);
+}
+
+static const struct spi_device_id bmi088_accel_id[] = {
+	{"bmi088-accel", },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, bmi088_accel_id);
+
+static struct spi_driver bmi088_accel_driver = {
+	.driver = {
+		.name	= "bmi088_accel_spi",
+		.pm	= &bmi088_accel_pm_ops,
+	},
+	.probe		= bmi088_accel_probe,
+	.remove		= bmi088_accel_remove,
+	.id_table	= bmi088_accel_id,
+};
+module_spi_driver(bmi088_accel_driver);
+
+MODULE_AUTHOR("Niek van Agt <niek.van.agt@topicproducts.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("BMI088 accelerometer driver (SPI)");

drivers/iio/accel/bmi088-accel.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BMI088_ACCEL_H
+#define BMI088_ACCEL_H
+
+#include <linux/pm.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+struct device;
+
+extern const struct regmap_config bmi088_regmap_conf;
+extern const struct dev_pm_ops bmi088_accel_pm_ops;
+
+int bmi088_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
+			    const char *name, bool block_supported);
+int bmi088_accel_core_remove(struct device *dev);
+
+#endif /* BMI088_ACCEL_H */