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From:   Song Qiang <songqiang1304521@gmail.com>
To:     jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de,
        pmeerw@pmeerw.net, robh+dt@kernel.org, mark.rutland@arm.com
Cc:     linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Song Qiang <songqiang1304521@gmail.com>
Subject: [PATCH] iio: magnetometer: Add support for PNI RM3100 9-axis magnetometer
Date:   Thu, 20 Sep 2018 21:13:40 +0800
Message-Id: <20180920131340.6699-1-songqiang1304521@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

PNI RM3100 magnetometer is a high resolution, large signal immunity
magnetometer, composed of 3 single sensors and a processing chip.
PNI is currently not in the vendors list, so this is also adding it.

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

Signed-off-by: Song Qiang <songqiang1304521@gmail.com>
---
 .../bindings/iio/magnetometer/pni,rm3100.txt  |  57 +++
 .../devicetree/bindings/vendor-prefixes.txt   |   1 +
 MAINTAINERS                                   |  10 +
 drivers/iio/magnetometer/Kconfig              |  29 ++
 drivers/iio/magnetometer/Makefile             |   4 +
 drivers/iio/magnetometer/rm3100-core.c        | 399 ++++++++++++++++++
 drivers/iio/magnetometer/rm3100-i2c.c         |  66 +++
 drivers/iio/magnetometer/rm3100-spi.c         |  72 ++++
 drivers/iio/magnetometer/rm3100.h             |  90 ++++
 9 files changed, 728 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
 create mode 100644 drivers/iio/magnetometer/rm3100-core.c
 create mode 100644 drivers/iio/magnetometer/rm3100-i2c.c
 create mode 100644 drivers/iio/magnetometer/rm3100-spi.c
 create mode 100644 drivers/iio/magnetometer/rm3100.h

diff --git a/Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt b/Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
new file mode 100644
index 000000000000..d0d2063e943f
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
@@ -0,0 +1,57 @@
+* PNI RM3100 9-axis magnetometer sensor
+
+I2C Bus:
+
+Required properties:
+
+- compatible : should be "pni,rm3100-i2c"
+- reg : the I2C address of the magnetometer
+
+Optional properties:
+
+- interrupts: data ready (DRDY) from the chip.
+  The interrupts can be triggered on rising edges.
+
+	Refer to interrupt-controller/interrupts.txt for generic
+	interrupt client node bindings.
+
+- pinctrl-*: pinctrl setup for DRDY line.
+
+Example:
+
+rm3100: rm3100@20 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&rm3100_pins>;
+
+	compatible = "pni,rm3100-i2c";
+	reg = <0x20>;
+	interrupt-parent = <&gpio0>;
+	interrupts = <4 IRQ_TYPE_EDGE_RISING>;
+};
+
+SPI Bus:
+
+Required properties:
+
+- compatible : should be "pni,rm3100-spi"
+- reg : address of sensor, usually 0 or 1.
+
+Optional properties:
+
+- interrupts: data ready (DRDY) from the chip.
+  The interrupts can be triggered on rising edges.
+
+	Refer to interrupt-controller/interrupts.txt for generic
+	interrupt client node bindings.
+
+- pinctrl-*: pinctrl setup for DRDY line, depands on archtechture.
+
+Example:
+
+rm3100: rm3100@0{
+	compatible = "pni,rm3100-spi";
+	reg = <0>;
+
+	interrupt-parent = <&gpio0>;
+	interrupts = <4 IRQ_TYPE_EDGE_RISING>;
+};
diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
index 41f0b97eb933..5bf3395fe9ae 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.txt
+++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
@@ -288,6 +288,7 @@ pine64	Pine64
 pixcir  PIXCIR MICROELECTRONICS Co., Ltd
 plathome	Plat'Home Co., Ltd.
 plda	PLDA
+pni     PNI
 portwell	Portwell Inc.
 poslab	Poslab Technology Co., Ltd.
 powervr	PowerVR (deprecated, use img)
diff --git a/MAINTAINERS b/MAINTAINERS
index 967ce8cdd1cc..30ee8cf98312 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11393,6 +11393,16 @@ 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-core.c
+F:	drivers/iio/magnetometer/rm3100-i2c.c
+F:	drivers/iio/magnetometer/rm3100-spi.c
+F:	drivers/iio/magnetometer/rm3100.h
+F:	Documentation/devicetree/bindings/iio/magnetometer/rm3100.txt
+
 POSIX CLOCKS and TIMERS
 M:	Thomas Gleixner <tglx@linutronix.de>
 L:	linux-kernel@vger.kernel.org
diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
index ed9d776d01af..f130b866a4fc 100644
--- a/drivers/iio/magnetometer/Kconfig
+++ b/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 9-Axis Magnetometer (I2C)"
+	depends on I2C
+	select SENSORS_RM3100
+	select REGMAP_I2C
+	help
+	  Say Y here to add support for the PNI RM3100 9-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 9-Axis Magnetometer (SPI)"
+	depends on SPI_MASTER
+	select SENSORS_RM3100
+	select REGMAP_SPI
+	help
+	  Say Y here to add support for the PNI RM3100 9-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
diff --git a/drivers/iio/magnetometer/Makefile b/drivers/iio/magnetometer/Makefile
index 664b2f866472..ba1bc34b82fa 100644
--- a/drivers/iio/magnetometer/Makefile
+++ b/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
diff --git a/drivers/iio/magnetometer/rm3100-core.c b/drivers/iio/magnetometer/rm3100-core.c
new file mode 100644
index 000000000000..55d515e0fe67
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100-core.c
@@ -0,0 +1,399 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * PNI RM3100 9-axis geomagnetic sensor driver core.
+ *
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ *
+ * User Manual available at
+ * <https://www.pnicorp.com/download/rm3100-user-manual/>
+ *
+ * TODO: Scale channel, event generaton, pm.
+ */
+
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+
+#include "rm3100.h"
+
+static const struct regmap_range rm3100_readable_ranges[] = {
+		regmap_reg_range(RM_W_REG_START, RM_W_REG_END),
+};
+
+const struct regmap_access_table rm3100_readable_table = {
+		.yes_ranges = rm3100_readable_ranges,
+		.n_yes_ranges = ARRAY_SIZE(rm3100_readable_ranges),
+};
+
+static const struct regmap_range rm3100_writable_ranges[] = {
+		regmap_reg_range(RM_R_REG_START, RM_R_REG_END),
+};
+
+const struct regmap_access_table rm3100_writable_table = {
+		.yes_ranges = rm3100_writable_ranges,
+		.n_yes_ranges = ARRAY_SIZE(rm3100_writable_ranges),
+};
+
+static const struct regmap_range rm3100_volatile_ranges[] = {
+		regmap_reg_range(RM_V_REG_START, RM_V_REG_END),
+};
+
+const struct regmap_access_table rm3100_volatile_table = {
+		.yes_ranges = rm3100_volatile_ranges,
+		.n_yes_ranges = ARRAY_SIZE(rm3100_volatile_ranges),
+};
+
+static irqreturn_t rm3100_measurement_irq_handler(int irq, void *d)
+{
+	struct rm3100_data *data = d;
+
+	complete(&data->measuring_done);
+
+	return IRQ_HANDLED;
+}
+
+static int rm3100_wait_measurement(struct rm3100_data *data)
+{
+	struct regmap *regmap = data->regmap;
+	unsigned int val;
+	u16 tries = 20;
+	int ret;
+
+	/* A read cycle of 400kbits i2c bus is about 20us, plus the time
+	 * used for schduling, a read cycle of fast mode of this device
+	 * can reach 1.7ms, it may be possible for data arrives just
+	 * after we check the RM_REG_STATUS. In this case, irq_handler is
+	 * called before measuring_done is reinitialized, it will wait
+	 * forever for a data that has already been ready.
+	 * Reinitialize measuring_done before looking up makes sure we
+	 * will always capture interrupt no matter when it happened.
+	 */
+	if (data->use_interrupt)
+		reinit_completion(&data->measuring_done);
+
+	ret = regmap_read(regmap, RM_REG_STATUS, &val);
+	if (ret < 0)
+		return ret;
+
+	if ((val & RM_STATUS_DRDY) != RM_STATUS_DRDY) {
+		if (data->use_interrupt) {
+			ret = wait_for_completion_timeout(&data->measuring_done,
+				msecs_to_jiffies(data->conversion_time));
+			if (!ret)
+				return -ETIMEDOUT;
+		} else {
+			do {
+				ret = regmap_read(regmap, RM_REG_STATUS, &val);
+				if (ret < 0)
+					return ret;
+
+				if (val & RM_STATUS_DRDY)
+					break;
+
+				usleep_range(1000, 5000);
+			} while (--tries);
+			if (!tries)
+				return -ETIMEDOUT;
+		}
+	}
+	return 0;
+}
+
+static int rm3100_read_mag(struct rm3100_data *data, int idx, int *val)
+{
+	struct regmap *regmap = data->regmap;
+	u8 buffer[3];
+	int ret;
+
+	mutex_lock(&data->lock);
+	ret = rm3100_wait_measurement(data);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	ret = regmap_bulk_read(regmap, RM_REG_MX2 + 3 * idx, buffer, 3);
+	mutex_unlock(&data->lock);
+	if (ret < 0)
+		return ret;
+
+	*val = le32_to_cpu((buffer[0] << 16) + (buffer[1] << 8) + buffer[2]);
+	*val = sign_extend32(*val, 23);
+
+	return IIO_VAL_INT;
+}
+
+#define RM_CHANNEL(axis, idx)					\
+	{								\
+		.type = IIO_MAGN,					\
+		.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),\
+		.scan_index = idx,					\
+		.scan_type = {						\
+			.sign = 's',					\
+			.realbits = 24,					\
+			.storagebits = 32,				\
+			.shift = 8,					\
+			.endianness = IIO_LE,				\
+		},							\
+	}
+
+static const struct iio_chan_spec rm3100_channels[] = {
+	RM_CHANNEL(X, 0),
+	RM_CHANNEL(Y, 1),
+	RM_CHANNEL(Z, 2),
+	IIO_CHAN_SOFT_TIMESTAMP(3),
+};
+
+static const unsigned long rm3100_scan_masks[] = {GENMASK(2, 0), 0};
+
+#define RM_SAMP_NUM	14
+
+/* Frequency : rm3100_samp_rates[][0].rm3100_samp_rates[][1]Hz.
+ * Time between reading: rm3100_sam_rates[][2]ms (The first on is actially 1.7).
+ */
+static const int rm3100_samp_rates[RM_SAMP_NUM][3] = {
+	{600, 0, 2}, {300, 0, 3}, {150, 0, 7}, {75, 0, 13}, {37, 0, 27},
+	{18, 0, 55}, {9, 0, 110}, {4, 500000, 220}, {2, 300000, 440},
+	{1, 200000, 800}, {0, 600000, 1600}, {0, 300000, 3300},
+	{0, 15000, 6700},  {0, 75000, 13000}
+};
+
+static int rm3100_get_samp_freq(struct rm3100_data *data, int *val, int *val2)
+{
+	int ret;
+	int tmp;
+
+	ret = regmap_read(data->regmap, RM_REG_TMRC, &tmp);
+	if (ret < 0)
+		return ret;
+	*val = rm3100_samp_rates[tmp-RM_TMRC_OFFSET][0];
+	*val2 = rm3100_samp_rates[tmp-RM_TMRC_OFFSET][1];
+
+	return IIO_VAL_INT_PLUS_MICRO;
+}
+
+static int rm3100_set_samp_freq(struct rm3100_data *data, int val, int val2)
+{
+	struct regmap *regmap = data->regmap;
+	int cycle_count;
+	int ret;
+	int i;
+
+	/* All cycle count registers use the same value. */
+	ret = regmap_read(regmap, RM_REG_CCXL, &cycle_count);
+	if (cycle_count < 0)
+		return cycle_count;
+
+	for (i = 0; i < RM_SAMP_NUM; i++) {
+		if (val == rm3100_samp_rates[i][0] &&
+			val2 == rm3100_samp_rates[i][1])
+			break;
+	}
+
+	if (i != RM_SAMP_NUM) {
+		mutex_lock(&data->lock);
+		ret = regmap_write(regmap, RM_REG_TMRC, i + RM_TMRC_OFFSET);
+		if (ret < 0)
+			return ret;
+
+		/* Checking if cycle count registers need changing. */
+		if (val == 600 && cycle_count == 200) {
+			for (i = 0; i < 3; i++) {
+				regmap_write(regmap, RM_REG_CCXL + 2 * i, 100);
+				if (ret < 0)
+					return ret;
+			}
+		} else if (val != 600 && cycle_count == 100) {
+			for (i = 0; i < 3; i++) {
+				regmap_write(regmap, RM_REG_CCXL + 2 * i, 200);
+				if (ret < 0)
+					return ret;
+			}
+		}
+		/* Writing TMRC registers requires CMM reset. */
+		ret = regmap_write(regmap, RM_REG_CMM, 0);
+		if (ret < 0)
+			return ret;
+		ret = regmap_write(regmap, RM_REG_CMM, RM_CMM_PMX |
+			RM_CMM_PMY | RM_CMM_PMZ | RM_CMM_START);
+		if (ret < 0)
+			return ret;
+		mutex_unlock(&data->lock);
+
+		data->conversion_time = rm3100_samp_rates[i][2] + 3000;
+		return 0;
+	}
+	return -EINVAL;
+}
+
+static int rm3100_read_raw(struct iio_dev *indio_dev,
+			   const struct iio_chan_spec *chan,
+			   int *val, int *val2, long mask)
+{
+	struct rm3100_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret < 0)
+			return ret;
+		ret = rm3100_read_mag(data, chan->scan_index, val);
+		iio_device_release_direct_mode(indio_dev);
+
+		return ret;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		return ret = rm3100_get_samp_freq(data, val, val2);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int rm3100_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long mask)
+{
+	struct rm3100_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		ret = rm3100_set_samp_freq(data, val, val2);
+		if (ret < 0)
+			return ret;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+
+}
+
+static const struct iio_info rm3100_info = {
+	.read_raw = rm3100_read_raw,
+	.write_raw = rm3100_write_raw,
+};
+
+static irqreturn_t rm3100_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct rm3100_data *data = iio_priv(indio_dev);
+	struct regmap *regmap = data->regmap;
+	u8 *buffer;
+	int ret;
+	int i;
+
+	buffer = devm_kzalloc(data->dev, indio_dev->scan_bytes, GFP_KERNEL);
+	if (!buffer)
+		goto done;
+
+	mutex_lock(&data->lock);
+	ret = rm3100_wait_measurement(data);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		goto done;
+	}
+
+	for (i = 0; i < 3; i++) {
+		ret = regmap_bulk_read(regmap, RM_REG_MX2 + 3 * i,
+				buffer + 4 * i, 3);
+		if (ret < 0)
+			return ret;
+	}
+	mutex_unlock(&data->lock);
+
+	iio_push_to_buffers_with_timestamp(indio_dev, buffer,
+			iio_get_time_ns(indio_dev));
+done:
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq)
+{
+	struct iio_dev *indio_dev;
+	struct rm3100_data *data;
+	int tmp;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	dev_set_drvdata(dev, indio_dev);
+	data->dev = dev;
+	data->regmap = regmap;
+
+	mutex_init(&data->lock);
+
+	indio_dev->dev.parent = dev;
+	indio_dev->name = "rm3100";
+	indio_dev->info = &rm3100_info;
+	indio_dev->channels = rm3100_channels;
+	indio_dev->num_channels = ARRAY_SIZE(rm3100_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->available_scan_masks = rm3100_scan_masks;
+
+	if (!irq)
+		data->use_interrupt = false;
+	else {
+		data->use_interrupt = true;
+		ret = devm_request_irq(dev,
+			irq,
+			rm3100_measurement_irq_handler,
+			IRQF_TRIGGER_RISING,
+			indio_dev->name,
+			data);
+		if (ret < 0) {
+			dev_err(dev,
+			"request irq line failed.");
+			return -ret;
+		}
+		init_completion(&data->measuring_done);
+	}
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+					rm3100_trigger_handler, NULL);
+	if (ret < 0)
+		return ret;
+
+	/* 3sec more wait time. */
+	ret = regmap_read(data->regmap, RM_REG_TMRC, &tmp);
+	data->conversion_time = rm3100_samp_rates[tmp-RM_TMRC_OFFSET][2] + 3000;
+
+	/* Starting all channels' conversion. */
+	ret = regmap_write(regmap, RM_REG_CMM,
+		RM_CMM_PMX | RM_CMM_PMY | RM_CMM_PMZ | RM_CMM_START);
+	if (ret < 0)
+		return ret;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+EXPORT_SYMBOL(rm3100_common_probe);
+
+int rm3100_common_remove(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct rm3100_data *data = iio_priv(indio_dev);
+	struct regmap *regmap = data->regmap;
+
+	regmap_write(regmap, RM_REG_CMM, 0x00);
+
+	return 0;
+}
+EXPORT_SYMBOL(rm3100_common_remove);
+
+MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
+MODULE_DESCRIPTION("PNI RM3100 9-axis magnetometer i2c driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/iio/magnetometer/rm3100-i2c.c b/drivers/iio/magnetometer/rm3100-i2c.c
new file mode 100644
index 000000000000..b50dc5b1b30b
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100-i2c.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Support for PNI RM3100 9-axis geomagnetic sensor a i2c bus.
+ *
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ *
+ * User Manual available at
+ * <https://www.pnicorp.com/download/rm3100-user-manual/>
+ *
+ * i2c slave address 0x20 + SA1 << 1 + SA0.
+ */
+
+#include <linux/i2c.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;
+
+	if (!i2c_check_functionality(client->adapter,
+		I2C_FUNC_SMBUS_READ_I2C_BLOCK | I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EOPNOTSUPP;
+
+	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 int rm3100_remove(struct i2c_client *client)
+{
+	return rm3100_common_remove(&client->dev);
+}
+
+static const struct of_device_id rm3100_dt_match[] = {
+	{ .compatible = "pni,rm3100-i2c", },
+	{ }
+};
+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,
+	.remove = rm3100_remove,
+};
+module_i2c_driver(rm3100_driver);
+
+MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
+MODULE_DESCRIPTION("PNI RM3100 9-axis magnetometer i2c driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/iio/magnetometer/rm3100-spi.c b/drivers/iio/magnetometer/rm3100-spi.c
new file mode 100644
index 000000000000..2c7dd9e3a1a2
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100-spi.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Support for PNI RM3100 9-axis geomagnetic sensor a spi bus.
+ *
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ *
+ * User Manual available at
+ * <https://www.pnicorp.com/download/rm3100-user-manual/>
+ */
+
+#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 exceeds 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 int rm3100_remove(struct spi_device *spi)
+{
+	return rm3100_common_remove(&spi->dev);
+}
+
+static const struct of_device_id rm3100_dt_match[] = {
+	{ .compatible = "pni,rm3100-spi", },
+	{ }
+};
+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,
+		.remove = rm3100_remove,
+};
+module_spi_driver(rm3100_driver);
+
+MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
+MODULE_DESCRIPTION("PNI RM3100 9-axis magnetometer spi driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/iio/magnetometer/rm3100.h b/drivers/iio/magnetometer/rm3100.h
new file mode 100644
index 000000000000..5e30bc0f5149
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100.h
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Header file for PNI RM3100 driver
+ *
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ */
+
+#ifndef RM3100_CORE_H
+#define RM3100_CORE_H
+
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define RM_REG_REV_ID		0x36
+
+/* Cycle Count Registers MSBs and LSBs. */
+#define RM_REG_CCXM		0x04
+#define RM_REG_CCXL		0x05
+#define RM_REG_CCYM		0x06
+#define RM_REG_CCYL		0x07
+#define RM_REG_CCZM		0x08
+#define RM_REG_CCZL		0x09
+
+/* Single Measurement Mode register. */
+#define RM_REG_POLL		0x00
+#define RM_POLL_PMX		BIT(4)
+#define RM_POLL_PMY		BIT(5)
+#define RM_POLL_PMZ		BIT(6)
+
+/* Continues Measurement Mode register. */
+#define RM_REG_CMM		0x01
+#define RM_CMM_START		BIT(0)
+#define RM_CMM_DRDM		BIT(2)
+#define RM_CMM_PMX		BIT(4)
+#define RM_CMM_PMY		BIT(5)
+#define RM_CMM_PMZ		BIT(6)
+
+/* TiMe Rate Configuration register. */
+#define RM_REG_TMRC		0x0B
+#define RM_TMRC_OFFSET		0x92
+
+/* Result Status register. */
+#define RM_REG_STATUS		0x34
+#define RM_STATUS_DRDY		BIT(7)
+
+/* Measurement result registers. */
+#define RM_REG_MX2		0x24
+#define RM_REG_MX1		0x25
+#define RM_REG_MX0		0x26
+#define RM_REG_MY2		0x27
+#define RM_REG_MY1		0x28
+#define RM_REG_MY0		0x29
+#define RM_REG_MZ2		0x2a
+#define RM_REG_MZ1		0x2b
+#define RM_REG_MZ0		0x2c
+
+#define RM_REG_HSHAKE		0x35
+
+#define RM_W_REG_START		RM_REG_POLL
+#define RM_W_REG_END		RM_REG_REV_ID
+#define RM_R_REG_START		RM_REG_POLL
+#define RM_R_REG_END		RM_REG_HSHAKE
+#define RM_V_REG_START		RM_REG_MX2
+#define RM_V_REG_END		RM_REG_HSHAKE
+
+/* Built-In Self Test reigister. */
+#define RM_REG_BIST		0x33
+
+struct rm3100_data {
+	struct device *dev;
+	struct regmap *regmap;
+	struct completion measuring_done;
+	bool use_interrupt;
+
+	int conversion_time;
+
+	/* To protect consistency of every measurement and sampling
+	 * frequency change operations.
+	 */
+	struct mutex lock;
+};
+
+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);
+int rm3100_common_remove(struct device *dev);
+
+#endif /* RM3100_CORE_H */
-- 
2.17.1