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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:     preid@electromag.com.au, rtresidd@electromag.com.au,
        linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Song Qiang <songqiang1304521@gmail.com>
Subject: [PATCH 2/2] iio: magnetometer: Add driver support for PNI RM3100
Date:   Tue, 25 Sep 2018 11:17:24 +0800
Message-Id: <20180925031724.21399-2-songqiang1304521@gmail.com>
In-Reply-To: <20180925031724.21399-1-songqiang1304521@gmail.com>
References: <20180925031724.21399-1-songqiang1304521@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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

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>
---
Changes in v2:
	- Add scale channel.
	- Add EXPORT_SYMBOL_GPL() to export regmap confuguration
	  structures.
	- Add sampling frequency available attribute.
	- Clean up headers and License declarations.
	- Change axis number to 3.
	- Remove bus specific part in compatible string.
	- Remove le32_to_cpu().
	- Check cycle count registers at *_probe().
	- Format comments.
	- Spell check.
	- Change prefix from RM_* to RM3100_*.
	- Check all error return paths.
	- Add devm_add_action() to avoid race condition when remove.

 MAINTAINERS                            |   7 +
 drivers/iio/magnetometer/Kconfig       |  29 ++
 drivers/iio/magnetometer/Makefile      |   4 +
 drivers/iio/magnetometer/rm3100-core.c | 470 +++++++++++++++++++++++++
 drivers/iio/magnetometer/rm3100-i2c.c  |  58 +++
 drivers/iio/magnetometer/rm3100-spi.c  |  64 ++++
 drivers/iio/magnetometer/rm3100.h      |  73 ++++
 7 files changed, 705 insertions(+)
 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/MAINTAINERS b/MAINTAINERS
index 967ce8cdd1cc..14eeeb072403 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11393,6 +11393,13 @@ 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
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..5d28b53b7a04
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100-core.c
@@ -0,0 +1,470 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PNI RM3100 3-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: event generaton, pm.
+ */
+
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.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(RM3100_W_REG_START, RM3100_W_REG_END),
+};
+
+const struct regmap_access_table rm3100_readable_table = {
+	.yes_ranges = rm3100_readable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(rm3100_readable_ranges),
+};
+EXPORT_SYMBOL_GPL(rm3100_readable_table);
+
+static const struct regmap_range rm3100_writable_ranges[] = {
+	regmap_reg_range(RM3100_R_REG_START, RM3100_R_REG_END),
+};
+
+const struct regmap_access_table rm3100_writable_table = {
+	.yes_ranges = rm3100_writable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(rm3100_writable_ranges),
+};
+EXPORT_SYMBOL_GPL(rm3100_writable_table);
+
+static const struct regmap_range rm3100_volatile_ranges[] = {
+	regmap_reg_range(RM3100_V_REG_START, RM3100_V_REG_END),
+};
+
+const struct regmap_access_table rm3100_volatile_table = {
+	.yes_ranges = rm3100_volatile_ranges,
+	.n_yes_ranges = ARRAY_SIZE(rm3100_volatile_ranges),
+};
+EXPORT_SYMBOL_GPL(rm3100_volatile_table);
+
+static irqreturn_t rm3100_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;
+	int tries = 20;
+	int ret;
+
+	/*
+	 * A read cycle of 400kbits i2c; bus is about 20us, plus the time
+	 * used for scheduling, a read cycle of fast mode of this device
+	 * can reach 1.7ms, it may be possible for data to arrive just
+	 * after we check the RM3100_REG_STATUS. In this case, irq_handler is
+	 * called before measuring_done is reinitialized, it will wait
+	 * forever for 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, RM3100_REG_STATUS, &val);
+	if (ret < 0)
+		return ret;
+
+	if ((val & RM3100_STATUS_DRDY) != RM3100_STATUS_DRDY) {
+		if (data->use_interrupt) {
+			ret = wait_for_completion_timeout(&data->measuring_done,
+				msecs_to_jiffies(data->conversion_time));
+			if (ret < 0)
+				return -ETIMEDOUT;
+		} else {
+			do {
+				usleep_range(1000, 5000);
+
+				ret = regmap_read(regmap, RM3100_REG_STATUS,
+						  &val);
+				if (ret < 0)
+					return ret;
+
+				if (val & RM3100_STATUS_DRDY)
+					break;
+			} 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, RM3100_REG_MX2 + 3 * idx, buffer, 3);
+	mutex_unlock(&data->lock);
+	if (ret < 0)
+		return ret;
+
+	*val = sign_extend32((buffer[0] << 16) | (buffer[1] << 8) | buffer[2],
+			     23);
+
+	return IIO_VAL_INT;
+}
+
+#define RM3100_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_SCALE) |	\
+			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[] = {
+	RM3100_CHANNEL(X, 0),
+	RM3100_CHANNEL(Y, 1),
+	RM3100_CHANNEL(Z, 2),
+	IIO_CHAN_SOFT_TIMESTAMP(3),
+};
+
+static const unsigned long rm3100_scan_masks[] = {GENMASK(2, 0), 0};
+
+static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
+	"600 300 150 75 37 18 9 4.5 2.3 1.2 0.6 0.3 0.015 0.075"
+);
+
+static struct attribute *rm3100_attributes[] = {
+	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group rm3100_attribute_group = {
+	.attrs = rm3100_attributes,
+};
+
+#define RM3100_SAMP_NUM			14
+
+/*
+ * Frequency : rm3100_samp_rates[][0].rm3100_samp_rates[][1]Hz.
+ * Time between reading: rm3100_sam_rates[][2]ms.
+ * The first one is actually 1.7ms.
+ */
+static const int rm3100_samp_rates[RM3100_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;
+
+	mutex_lock(&data->lock);
+	ret = regmap_read(data->regmap, RM3100_REG_TMRC, &tmp);
+	mutex_unlock(&data->lock);
+	if (ret < 0)
+		return ret;
+	*val = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][0];
+	*val2 = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][1];
+
+	return IIO_VAL_INT_PLUS_MICRO;
+}
+
+static int rm3100_set_cycle_count(struct rm3100_data *data, int val)
+{
+	int ret;
+	u8 i;
+
+	for (i = 0; i < 3; i++) {
+		ret = regmap_write(data->regmap, RM3100_REG_CC_X + 2 * i, 100);
+		if (ret < 0)
+			return ret;
+	}
+	if (val == 50)
+		data->cycle_count_index = 0;
+	else if (val == 100)
+		data->cycle_count_index = 1;
+	else
+		data->cycle_count_index = 2;
+
+	return 0;
+}
+
+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;
+
+	mutex_lock(&data->lock);
+	/* All cycle count registers use the same value. */
+	ret = regmap_read(regmap, RM3100_REG_CC_X, &cycle_count);
+	if (ret < 0)
+		goto unlock_return;
+
+	for (i = 0; i < RM3100_SAMP_NUM; i++) {
+		if (val == rm3100_samp_rates[i][0] &&
+		    val2 == rm3100_samp_rates[i][1])
+			break;
+	}
+	if (i == RM3100_SAMP_NUM) {
+		ret = -EINVAL;
+		goto unlock_return;
+	}
+
+	ret = regmap_write(regmap, RM3100_REG_TMRC, i + RM3100_TMRC_OFFSET);
+	if (ret < 0)
+		goto unlock_return;
+
+	/* Checking if cycle count registers need changing. */
+	if (val == 600 && cycle_count == 200) {
+		ret = rm3100_set_cycle_count(data, 100);
+		if (ret < 0)
+			goto unlock_return;
+	} else if (val != 600 && cycle_count == 100) {
+		ret = rm3100_set_cycle_count(data, 200);
+		if (ret < 0)
+			goto unlock_return;
+	}
+
+	/* Writing TMRC registers requires CMM reset. */
+	ret = regmap_write(regmap, RM3100_REG_CMM, 0);
+	if (ret < 0)
+		goto unlock_return;
+	ret = regmap_write(regmap, RM3100_REG_CMM,
+		RM3100_CMM_X | RM3100_CMM_Y | RM3100_CMM_Z | RM3100_CMM_START);
+	mutex_unlock(&data->lock);
+	if (ret < 0)
+		return ret;
+
+	data->conversion_time = rm3100_samp_rates[i][2] + 3000;
+	return 0;
+
+unlock_return:
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
+/*
+ * Scale of this sensor depends on cycle count value, these three values
+ * are corresponding to cycle count value 50, 100, 200.
+ * scale = output / gain * 10e4.
+ */
+const static int rm3100_scale[] = {500, 263, 133};
+
+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) {
+			iio_device_release_direct_mode(indio_dev);
+			return ret;
+		}
+		ret = rm3100_read_mag(data, chan->scan_index, val);
+		iio_device_release_direct_mode(indio_dev);
+
+		return ret;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = rm3100_scale[data->cycle_count_index];
+
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		return 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);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		return rm3100_set_samp_freq(data, val, val2);
+	default:
+		return -EINVAL;
+	}
+
+}
+
+static const struct iio_info rm3100_info = {
+	.attrs = &rm3100_attribute_group,
+	.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[9];
+	int ret;
+	int i;
+
+	mutex_lock(&data->lock);
+	ret = rm3100_wait_measurement(data);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		goto done;
+	}
+
+	ret = regmap_bulk_read(regmap, RM3100_REG_MX2, buffer, sizeof(buffer));
+	mutex_unlock(&data->lock);
+	if (ret < 0)
+		goto done;
+
+	/* Convert XXXYYYZZZxxx to XXXxYYYxZZZx. x for padding. */
+	for (i = 0; i < 3; i++)
+		memcpy(data->buffer + i * 4, buffer + i * 3, 3);
+
+	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
+			iio_get_time_ns(indio_dev));
+
+done:
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static void rm3100_remove(void *dh)
+{
+	struct rm3100_data *data = (struct rm3100_data *)dh;
+	int ret;
+
+	ret = regmap_write(data->regmap, RM3100_REG_CMM, 0x00);
+	if (ret < 0)
+		dev_err(data->dev, "failed to stop device.\n");
+}
+
+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);
+	data->dev = dev;
+	data->regmap = regmap;
+	data->buffer = devm_kzalloc(dev, RM3100_SCAN_BYTES, GFP_KERNEL);
+	if (!data->buffer)
+		return -ENOMEM;
+
+	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_irq_handler,
+				       IRQF_TRIGGER_RISING,
+				       indio_dev->name,
+				       data);
+		if (ret < 0) {
+			dev_err(dev, "request irq line failed.\n");
+			return ret;
+		}
+		init_completion(&data->measuring_done);
+	}
+
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
+					      rm3100_trigger_handler, NULL);
+	if (ret < 0)
+		return ret;
+
+	/* 3sec more wait time. */
+	ret = regmap_read(regmap, RM3100_REG_TMRC, &tmp);
+	if (ret < 0)
+		return ret;
+	data->conversion_time =
+		rm3100_samp_rates[tmp-RM3100_TMRC_OFFSET][2] + 3000;
+
+	/* Cycle count values may not be what we want. */
+	ret = regmap_read(data->regmap, RM3100_REG_TMRC, &tmp);
+	if (ret < 0)
+		return ret;
+	if ((tmp - RM3100_TMRC_OFFSET) == 0)
+		rm3100_set_cycle_count(data, 100);
+	else
+		rm3100_set_cycle_count(data, 200);
+
+	/* Starting all channels' conversion. */
+	ret = regmap_write(regmap, RM3100_REG_CMM,
+		RM3100_CMM_X | RM3100_CMM_Y | RM3100_CMM_Z | RM3100_CMM_START);
+	if (ret < 0)
+		return ret;
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret < 0)
+		return ret;
+
+	return devm_add_action(dev, rm3100_remove, data);
+}
+EXPORT_SYMBOL_GPL(rm3100_common_probe);
+
+MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
+MODULE_DESCRIPTION("PNI RM3100 3-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..e8b84fac771b
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100-i2c.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for PNI RM3100 3-axis geomagnetic sensor a i2c bus.
+ *
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ *
+ * i2c slave address 0x20 + SA1 << 1 + SA0.
+ */
+
+#include <linux/module.h>
+#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 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");
diff --git a/drivers/iio/magnetometer/rm3100-spi.c b/drivers/iio/magnetometer/rm3100-spi.c
new file mode 100644
index 000000000000..1a7a69fb9872
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100-spi.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for PNI RM3100 3-axis geomagnetic sensor 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");
diff --git a/drivers/iio/magnetometer/rm3100.h b/drivers/iio/magnetometer/rm3100.h
new file mode 100644
index 000000000000..673647574add
--- /dev/null
+++ b/drivers/iio/magnetometer/rm3100.h
@@ -0,0 +1,73 @@
+/* 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/regmap.h>
+
+#define RM3100_REG_REV_ID		0x36
+
+/* Cycle Count Registers. */
+#define RM3100_REG_CC_X			0x05
+#define RM3100_REG_CC_Y			0x07
+#define RM3100_REG_CC_Z			0x09
+
+/* Continues Measurement Mode register. */
+#define RM3100_REG_CMM			0x01
+#define RM3100_CMM_START		BIT(0)
+#define RM3100_CMM_X			BIT(4)
+#define RM3100_CMM_Y			BIT(5)
+#define RM3100_CMM_Z			BIT(6)
+
+/* TiMe Rate Configuration register. */
+#define RM3100_REG_TMRC			0x0B
+#define RM3100_TMRC_OFFSET		0x92
+
+/* Result Status register. */
+#define RM3100_REG_STATUS		0x34
+#define RM3100_STATUS_DRDY		BIT(7)
+
+/* Measurement result registers. */
+#define RM3100_REG_MX2			0x24
+#define RM3100_REG_MY2			0x27
+#define RM3100_REG_MZ2			0x2a
+
+#define RM3100_W_REG_START		RM3100_REG_CMM
+#define RM3100_W_REG_END		RM3100_REG_REV_ID
+#define RM3100_R_REG_START		RM3100_REG_CMM
+#define RM3100_R_REG_END		RM3100_REG_STATUS
+#define RM3100_V_REG_START		RM3100_REG_MX2
+#define RM3100_V_REG_END		RM3100_REG_STATUS
+
+#define RM3100_SCAN_BYTES		24
+
+struct rm3100_data {
+	struct device *dev;
+	struct regmap *regmap;
+	struct completion measuring_done;
+	bool use_interrupt;
+
+	int conversion_time;
+	int cycle_count_index;
+
+	u8 *buffer;
+
+	/*
+	 * 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);
+
+#endif /* RM3100_CORE_H */
-- 
2.17.1