iio: magnetometer: Add driver support for PNI RM3100

PNI RM3100 is a high resolution, large signal immunity magnetometer,
composed of 3 single sensors and a processing chip with a MagI2C
interface.

Following functions are available:
 - Single-shot measurement from
   /sys/bus/iio/devices/iio:deviceX/in_magn_{axis}_raw
 - Triggerd buffer measurement.
 - DRDY pin for data ready trigger.
 - Both i2c and spi interface are supported.
 - Both interrupt and polling measurement is supported, depends on if
   the 'interrupts' in DT is declared.

Signed-off-by: Song Qiang <songqiang1304521@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -11607,6 +11607,13 @@ M:	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
 S:	Maintained
 F:	drivers/pnp/
 
+PNI RM3100 IIO DRIVER
+M:	Song Qiang <songqiang1304521@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/iio/magnetometer/rm3100*
+F:	Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
+
 POSIX CLOCKS and TIMERS
 M:	Thomas Gleixner <tglx@linutronix.de>
 L:	linux-kernel@vger.kernel.org

drivers/iio/magnetometer/Kconfig

@@ -175,4 +175,33 @@ config SENSORS_HMC5843_SPI
 	  - hmc5843_core (core functions)
 	  - hmc5843_spi (support for HMC5983)
 
+config SENSORS_RM3100
+	tristate
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+
+config SENSORS_RM3100_I2C
+	tristate "PNI RM3100 3-Axis Magnetometer (I2C)"
+	depends on I2C
+	select SENSORS_RM3100
+	select REGMAP_I2C
+	help
+	  Say Y here to add support for the PNI RM3100 3-Axis Magnetometer.
+
+	  This driver can also be compiled as a module.
+	  To compile this driver as a module, choose M here: the module
+	  will be called rm3100-i2c.
+
+config SENSORS_RM3100_SPI
+	tristate "PNI RM3100 3-Axis Magnetometer (SPI)"
+	depends on SPI_MASTER
+	select SENSORS_RM3100
+	select REGMAP_SPI
+	help
+	  Say Y here to add support for the PNI RM3100 3-Axis Magnetometer.
+
+	  This driver can also be compiled as a module.
+	  To compile this driver as a module, choose M here: the module
+	  will be called rm3100-spi.
+
 endmenu

drivers/iio/magnetometer/Makefile

@@ -24,3 +24,7 @@ obj-$(CONFIG_IIO_ST_MAGN_SPI_3AXIS) += st_magn_spi.o
 obj-$(CONFIG_SENSORS_HMC5843)		+= hmc5843_core.o
 obj-$(CONFIG_SENSORS_HMC5843_I2C)	+= hmc5843_i2c.o
 obj-$(CONFIG_SENSORS_HMC5843_SPI)	+= hmc5843_spi.o
+
+obj-$(CONFIG_SENSORS_RM3100)		+= rm3100-core.o
+obj-$(CONFIG_SENSORS_RM3100_I2C)	+= rm3100-i2c.o
+obj-$(CONFIG_SENSORS_RM3100_SPI)	+= rm3100-spi.o

drivers/iio/magnetometer/rm3100-i2c.c

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for PNI RM3100 3-axis geomagnetic sensor on a i2c bus.
+ *
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ *
+ * i2c slave address: 0x20 + SA1 << 1 + SA0.
+ */
+
+#include <linux/i2c.h>
+#include <linux/module.h>
+
+#include "rm3100.h"
+
+static const struct regmap_config rm3100_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.rd_table = &rm3100_readable_table,
+	.wr_table = &rm3100_writable_table,
+	.volatile_table = &rm3100_volatile_table,
+
+	.cache_type = REGCACHE_RBTREE,
+};
+
+static int rm3100_probe(struct i2c_client *client)
+{
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init_i2c(client, &rm3100_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return rm3100_common_probe(&client->dev, regmap, client->irq);
+}
+
+static const struct of_device_id rm3100_dt_match[] = {
+	{ .compatible = "pni,rm3100", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, rm3100_dt_match);
+
+static struct i2c_driver rm3100_driver = {
+	.driver = {
+		.name = "rm3100-i2c",
+		.of_match_table = rm3100_dt_match,
+	},
+	.probe_new = rm3100_probe,
+};
+module_i2c_driver(rm3100_driver);
+
+MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
+MODULE_DESCRIPTION("PNI RM3100 3-axis magnetometer i2c driver");
+MODULE_LICENSE("GPL v2");

drivers/iio/magnetometer/rm3100-spi.c

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for PNI RM3100 3-axis geomagnetic sensor on a spi bus.
+ *
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ */
+
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+
+#include "rm3100.h"
+
+static const struct regmap_config rm3100_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.rd_table = &rm3100_readable_table,
+	.wr_table = &rm3100_writable_table,
+	.volatile_table = &rm3100_volatile_table,
+
+	.read_flag_mask = 0x80,
+
+	.cache_type = REGCACHE_RBTREE,
+};
+
+static int rm3100_probe(struct spi_device *spi)
+{
+	struct regmap *regmap;
+	int ret;
+
+	/* Actually this device supports both mode 0 and mode 3. */
+	spi->mode = SPI_MODE_0;
+	/* Data rates cannot exceed 1Mbits. */
+	spi->max_speed_hz = 1000000;
+	spi->bits_per_word = 8;
+	ret = spi_setup(spi);
+	if (ret)
+		return ret;
+
+	regmap = devm_regmap_init_spi(spi, &rm3100_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return rm3100_common_probe(&spi->dev, regmap, spi->irq);
+}
+
+static const struct of_device_id rm3100_dt_match[] = {
+	{ .compatible = "pni,rm3100", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, rm3100_dt_match);
+
+static struct spi_driver rm3100_driver = {
+	.driver = {
+		.name = "rm3100-spi",
+		.of_match_table = rm3100_dt_match,
+	},
+	.probe = rm3100_probe,
+};
+module_spi_driver(rm3100_driver);
+
+MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
+MODULE_DESCRIPTION("PNI RM3100 3-axis magnetometer spi driver");
+MODULE_LICENSE("GPL v2");

drivers/iio/magnetometer/rm3100.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ */
+
+#ifndef RM3100_CORE_H
+#define RM3100_CORE_H
+
+#include <linux/regmap.h>
+
+extern const struct regmap_access_table rm3100_readable_table;
+extern const struct regmap_access_table rm3100_writable_table;
+extern const struct regmap_access_table rm3100_volatile_table;
+
+int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq);
+
+#endif /* RM3100_CORE_H */