iio: magn: add a driver for AK8974

This adds a driver for the Asahi Kasei AK8974 and its sibling
AMI305 magnetometers. It was deployed on scale in 2009 on a
multitude of devices. It is distincly different from AK8973
and AK8975 and needs its own driver.

This patch is based on the long lost work of Samu Onkalo at Nokia,
who made a misc character device driver for the Maemo/MeeGo Nokia
devices, before the time of the IIO subsystem. It was mounted in e.g.
the Nokia N950, N8, N86, N97 etc. It is also mounted on the
ST-Ericsson HREF reference designs.

It works nicely in sysfs:

$ cat in_magn_x_raw && cat in_magn_y_raw && cat in_magn_z_raw
-55
-101
161

And with buffered reads using a simple HRTimer trigger:
$ generic_buffer -c10 -a -n ak8974 -t foo
iio device number being used is 3
iio trigger number being used is 2
No channels are enabled, enabling all channels
Enabling: in_magn_x_en
Enabling: in_magn_y_en
Enabling: in_magn_z_en
Enabling: in_timestamp_en
/sys/bus/iio/devices/iio:device3 foo
-58.000000 -102.000000 157.000000 946684970985321044
-60.000000 -98.000000 159.000000 946684971012237548
-60.000000 -106.000000 163.000000 946684971032257080
-62.000000 -94.000000 169.000000 946684971052185058
-58.000000 -98.000000 163.000000 946684971072204589
-54.000000 -100.000000 163.000000 946684971092224121
-53.000000 -103.000000 164.000000 946684971112731933
-50.000000 -102.000000 165.000000 946684971132232666
-61.000000 -101.000000 164.000000 946684971152191162
-57.000000 -99.000000 168.000000 946684971172210693
Disabling: in_magn_x_en
Disabling: in_magn_y_en
Disabling: in_magn_z_en
Disabling: in_timestamp_en

I cannot currently scale these raw values to gauss. This is
because of lack of documentation. I have sent a request for
a datasheet to Asahi Kasei.

The driver can optionally use a DRDY line IRQ to capture data,
else it will sleep and poll.

Cc: Samu Onkalo <samu.onkalo@intel.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Tested-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

MAINTAINERS

@@ -1930,6 +1930,13 @@ S:	Maintained
 F:	drivers/media/i2c/as3645a.c
 F:	include/media/i2c/as3645a.h
 
+ASAHI KASEI AK8974 DRIVER
+M:	Linus Walleij <linus.walleij@linaro.org>
+L:	linux-iio@vger.kernel.org
+W:	http://www.akm.com/
+S:	Supported
+F:	drivers/iio/magnetometer/ak8974.c
+
 ASC7621 HARDWARE MONITOR DRIVER
 M:	George Joseph <george.joseph@fairview5.com>
 L:	linux-hwmon@vger.kernel.org

drivers/iio/magnetometer/Kconfig

@@ -5,8 +5,22 @@
 
 menu "Magnetometer sensors"
 
+config AK8974
+	tristate "Asahi Kasei AK8974 3-Axis Magnetometer"
+	depends on I2C
+	depends on OF
+	select REGMAP_I2C
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for Asahi Kasei AK8974 or
+	  AMI305 I2C-based 3-axis magnetometer chips.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ak8974.
+
 config AK8975
-	tristate "Asahi Kasei AK 3-Axis Magnetometer"
+	tristate "Asahi Kasei AK8975 3-Axis Magnetometer"
 	depends on I2C
 	depends on GPIOLIB || COMPILE_TEST
 	select IIO_BUFFER

drivers/iio/magnetometer/Makefile

@@ -3,6 +3,7 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AK8974)	+= ak8974.o
 obj-$(CONFIG_AK8975)	+= ak8975.o
 obj-$(CONFIG_BMC150_MAGN) += bmc150_magn.o
 obj-$(CONFIG_BMC150_MAGN_I2C) += bmc150_magn_i2c.o

drivers/iio/magnetometer/ak8974.c

+/*
+ * Driver for the Asahi Kasei EMD Corporation AK8974
+ * and Aichi Steel AMI305 magnetometer chips.
+ * Based on a patch from Samu Onkalo and the AK8975 IIO driver.
+ *
+ * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
+ * Copyright (c) 2010 NVIDIA Corporation.
+ * Copyright (C) 2016 Linaro Ltd.
+ *
+ * Author: Samu Onkalo <samu.p.onkalo@nokia.com>
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h> /* For irq_get_irq_data() */
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/bitops.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/pm_runtime.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+/*
+ * 16-bit registers are little-endian. LSB is at the address defined below
+ * and MSB is at the next higher address.
+ */
+
+/* These registers are common for AK8974 and AMI305 */
+#define AK8974_SELFTEST		0x0C
+#define AK8974_SELFTEST_IDLE	0x55
+#define AK8974_SELFTEST_OK	0xAA
+
+#define AK8974_INFO		0x0D
+
+#define AK8974_WHOAMI		0x0F
+#define AK8974_WHOAMI_VALUE_AMI305 0x47
+#define AK8974_WHOAMI_VALUE_AK8974 0x48
+
+#define AK8974_DATA_X		0x10
+#define AK8974_DATA_Y		0x12
+#define AK8974_DATA_Z		0x14
+#define AK8974_INT_SRC		0x16
+#define AK8974_STATUS		0x18
+#define AK8974_INT_CLEAR	0x1A
+#define AK8974_CTRL1		0x1B
+#define AK8974_CTRL2		0x1C
+#define AK8974_CTRL3		0x1D
+#define AK8974_INT_CTRL		0x1E
+#define AK8974_INT_THRES	0x26  /* Absolute any axis value threshold */
+#define AK8974_PRESET		0x30
+
+/* AK8974-specific offsets */
+#define AK8974_OFFSET_X		0x20
+#define AK8974_OFFSET_Y		0x22
+#define AK8974_OFFSET_Z		0x24
+/* AMI305-specific offsets */
+#define AMI305_OFFSET_X		0x6C
+#define AMI305_OFFSET_Y		0x72
+#define AMI305_OFFSET_Z		0x78
+
+/* Different temperature registers */
+#define AK8974_TEMP		0x31
+#define AMI305_TEMP		0x60
+
+#define AK8974_INT_X_HIGH	BIT(7) /* Axis over +threshold  */
+#define AK8974_INT_Y_HIGH	BIT(6)
+#define AK8974_INT_Z_HIGH	BIT(5)
+#define AK8974_INT_X_LOW	BIT(4) /* Axis below -threshold	*/
+#define AK8974_INT_Y_LOW	BIT(3)
+#define AK8974_INT_Z_LOW	BIT(2)
+#define AK8974_INT_RANGE	BIT(1) /* Range overflow (any axis) */
+
+#define AK8974_STATUS_DRDY	BIT(6) /* Data ready */
+#define AK8974_STATUS_OVERRUN	BIT(5) /* Data overrun */
+#define AK8974_STATUS_INT	BIT(4) /* Interrupt occurred */
+
+#define AK8974_CTRL1_POWER	BIT(7) /* 0 = standby; 1 = active */
+#define AK8974_CTRL1_RATE	BIT(4) /* 0 = 10 Hz; 1 = 20 Hz	 */
+#define AK8974_CTRL1_FORCE_EN	BIT(1) /* 0 = normal; 1 = force	 */
+#define AK8974_CTRL1_MODE2	BIT(0) /* 0 */
+
+#define AK8974_CTRL2_INT_EN	BIT(4)  /* 1 = enable interrupts	      */
+#define AK8974_CTRL2_DRDY_EN	BIT(3)  /* 1 = enable data ready signal */
+#define AK8974_CTRL2_DRDY_POL	BIT(2)  /* 1 = data ready active high   */
+#define AK8974_CTRL2_RESDEF	(AK8974_CTRL2_DRDY_POL)
+
+#define AK8974_CTRL3_RESET	BIT(7) /* Software reset		  */
+#define AK8974_CTRL3_FORCE	BIT(6) /* Start forced measurement */
+#define AK8974_CTRL3_SELFTEST	BIT(4) /* Set selftest register	  */
+#define AK8974_CTRL3_RESDEF	0x00
+
+#define AK8974_INT_CTRL_XEN	BIT(7) /* Enable interrupt for this axis */
+#define AK8974_INT_CTRL_YEN	BIT(6)
+#define AK8974_INT_CTRL_ZEN	BIT(5)
+#define AK8974_INT_CTRL_XYZEN	(BIT(7)|BIT(6)|BIT(5))
+#define AK8974_INT_CTRL_POL	BIT(3) /* 0 = active low; 1 = active high */
+#define AK8974_INT_CTRL_PULSE	BIT(1) /* 0 = latched; 1 = pulse (50 usec) */
+#define AK8974_INT_CTRL_RESDEF	(AK8974_INT_CTRL_XYZEN | AK8974_INT_CTRL_POL)
+
+/* The AMI305 has elaborate FW version and serial number registers */
+#define AMI305_VER		0xE8
+#define AMI305_SN		0xEA
+
+#define AK8974_MAX_RANGE	2048
+
+#define AK8974_POWERON_DELAY	50
+#define AK8974_ACTIVATE_DELAY	1
+#define AK8974_SELFTEST_DELAY	1
+/*
+ * Set the autosuspend to two orders of magnitude larger than the poweron
+ * delay to make sane reasonable power tradeoff savings (5 seconds in
+ * this case).
+ */
+#define AK8974_AUTOSUSPEND_DELAY 5000
+
+#define AK8974_MEASTIME		3
+
+#define AK8974_PWR_ON		1
+#define AK8974_PWR_OFF		0
+
+/**
+ * struct ak8974 - state container for the AK8974 driver
+ * @i2c: parent I2C client
+ * @orientation: mounting matrix, flipped axis etc
+ * @map: regmap to access the AK8974 registers over I2C
+ * @regs: the avdd and dvdd power regulators
+ * @name: the name of the part
+ * @variant: the whoami ID value (for selecting code paths)
+ * @lock: locks the magnetometer for exclusive use during a measurement
+ * @drdy_irq: uses the DRDY IRQ line
+ * @drdy_complete: completion for DRDY
+ * @drdy_active_low: the DRDY IRQ is active low
+ */
+struct ak8974 {
+	struct i2c_client *i2c;
+	struct iio_mount_matrix orientation;
+	struct regmap *map;
+	struct regulator_bulk_data regs[2];
+	const char *name;
+	u8 variant;
+	struct mutex lock;
+	bool drdy_irq;
+	struct completion drdy_complete;
+	bool drdy_active_low;
+};
+
+static const char ak8974_reg_avdd[] = "avdd";
+static const char ak8974_reg_dvdd[] = "dvdd";
+
+static int ak8974_set_power(struct ak8974 *ak8974, bool mode)
+{
+	int ret;
+	u8 val;
+
+	val = mode ? AK8974_CTRL1_POWER : 0;
+	val |= AK8974_CTRL1_FORCE_EN;
+	ret = regmap_write(ak8974->map, AK8974_CTRL1, val);
+	if (ret < 0)
+		return ret;
+
+	if (mode)
+		msleep(AK8974_ACTIVATE_DELAY);
+
+	return 0;
+}
+
+static int ak8974_reset(struct ak8974 *ak8974)
+{
+	int ret;
+
+	/* Power on to get register access. Sets CTRL1 reg to reset state */
+	ret = ak8974_set_power(ak8974, AK8974_PWR_ON);
+	if (ret)
+		return ret;
+	ret = regmap_write(ak8974->map, AK8974_CTRL2, AK8974_CTRL2_RESDEF);
+	if (ret)
+		return ret;
+	ret = regmap_write(ak8974->map, AK8974_CTRL3, AK8974_CTRL3_RESDEF);
+	if (ret)
+		return ret;
+	ret = regmap_write(ak8974->map, AK8974_INT_CTRL,
+			   AK8974_INT_CTRL_RESDEF);
+	if (ret)
+		return ret;
+
+	/* After reset, power off is default state */
+	return ak8974_set_power(ak8974, AK8974_PWR_OFF);
+}
+
+static int ak8974_configure(struct ak8974 *ak8974)
+{
+	int ret;
+
+	ret = regmap_write(ak8974->map, AK8974_CTRL2, AK8974_CTRL2_DRDY_EN |
+			   AK8974_CTRL2_INT_EN);
+	if (ret)
+		return ret;
+	ret = regmap_write(ak8974->map, AK8974_CTRL3, 0);
+	if (ret)
+		return ret;
+	ret = regmap_write(ak8974->map, AK8974_INT_CTRL, AK8974_INT_CTRL_POL);
+	if (ret)
+		return ret;
+
+	return regmap_write(ak8974->map, AK8974_PRESET, 0);
+}
+
+static int ak8974_trigmeas(struct ak8974 *ak8974)
+{
+	unsigned int clear;
+	u8 mask;
+	u8 val;
+	int ret;
+
+	/* Clear any previous measurement overflow status */
+	ret = regmap_read(ak8974->map, AK8974_INT_CLEAR, &clear);
+	if (ret)
+		return ret;
+
+	/* If we have a DRDY IRQ line, use it */
+	if (ak8974->drdy_irq) {
+		mask = AK8974_CTRL2_INT_EN |
+			AK8974_CTRL2_DRDY_EN |
+			AK8974_CTRL2_DRDY_POL;
+		val = AK8974_CTRL2_DRDY_EN;
+
+		if (!ak8974->drdy_active_low)
+			val |= AK8974_CTRL2_DRDY_POL;
+
+		init_completion(&ak8974->drdy_complete);
+		ret = regmap_update_bits(ak8974->map, AK8974_CTRL2,
+					 mask, val);
+		if (ret)
+			return ret;
+	}
+
+	/* Force a measurement */
+	return regmap_update_bits(ak8974->map,
+				  AK8974_CTRL3,
+				  AK8974_CTRL3_FORCE,
+				  AK8974_CTRL3_FORCE);
+}
+
+static int ak8974_await_drdy(struct ak8974 *ak8974)
+{
+	int timeout = 2;
+	unsigned int val;
+	int ret;
+
+	if (ak8974->drdy_irq) {
+		ret = wait_for_completion_timeout(&ak8974->drdy_complete,
+					1 + msecs_to_jiffies(1000));
+		if (!ret) {
+			dev_err(&ak8974->i2c->dev,
+				"timeout waiting for DRDY IRQ\n");
+			return -ETIMEDOUT;
+		}
+		return 0;
+	}
+
+	/* Default delay-based poll loop */
+	do {
+		msleep(AK8974_MEASTIME);
+		ret = regmap_read(ak8974->map, AK8974_STATUS, &val);
+		if (ret < 0)
+			return ret;
+		if (val & AK8974_STATUS_DRDY)
+			return 0;
+	} while (--timeout);
+	if (!timeout) {
+		dev_err(&ak8974->i2c->dev,
+			"timeout waiting for DRDY\n");
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+static int ak8974_getresult(struct ak8974 *ak8974, s16 *result)
+{
+	unsigned int src;
+	int ret;
+
+	ret = ak8974_await_drdy(ak8974);
+	if (ret)
+		return ret;
+	ret = regmap_read(ak8974->map, AK8974_INT_SRC, &src);
+	if (ret < 0)
+		return ret;
+
+	/* Out of range overflow! Strong magnet close? */
+	if (src & AK8974_INT_RANGE) {
+		dev_err(&ak8974->i2c->dev,
+			"range overflow in sensor\n");
+		return -ERANGE;
+	}
+
+	ret = regmap_bulk_read(ak8974->map, AK8974_DATA_X, result, 6);
+	if (ret)
+		return ret;
+
+	return ret;
+}
+
+static irqreturn_t ak8974_drdy_irq(int irq, void *d)
+{
+	struct ak8974 *ak8974 = d;
+
+	if (!ak8974->drdy_irq)
+		return IRQ_NONE;
+
+	/* TODO: timestamp here to get good measurement stamps */
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t ak8974_drdy_irq_thread(int irq, void *d)
+{
+	struct ak8974 *ak8974 = d;
+	unsigned int val;
+	int ret;
+
+	/* Check if this was a DRDY from us */
+	ret = regmap_read(ak8974->map, AK8974_STATUS, &val);
+	if (ret < 0) {
+		dev_err(&ak8974->i2c->dev, "error reading DRDY status\n");
+		return IRQ_HANDLED;
+	}
+	if (val & AK8974_STATUS_DRDY) {
+		/* Yes this was our IRQ */
+		complete(&ak8974->drdy_complete);
+		return IRQ_HANDLED;
+	}
+
+	/* We may be on a shared IRQ, let the next client check */
+	return IRQ_NONE;
+}
+
+static int ak8974_selftest(struct ak8974 *ak8974)
+{
+	struct device *dev = &ak8974->i2c->dev;
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(ak8974->map, AK8974_SELFTEST, &val);
+	if (ret)
+		return ret;
+	if (val != AK8974_SELFTEST_IDLE) {
+		dev_err(dev, "selftest not idle before test\n");
+		return -EIO;
+	}
+
+	/* Trigger self-test */
+	ret = regmap_update_bits(ak8974->map,
+			AK8974_CTRL3,
+			AK8974_CTRL3_SELFTEST,
+			AK8974_CTRL3_SELFTEST);
+	if (ret) {
+		dev_err(dev, "could not write CTRL3\n");
+		return ret;
+	}
+
+	msleep(AK8974_SELFTEST_DELAY);
+
+	ret = regmap_read(ak8974->map, AK8974_SELFTEST, &val);
+	if (ret)
+		return ret;
+	if (val != AK8974_SELFTEST_OK) {
+		dev_err(dev, "selftest result NOT OK (%02x)\n", val);
+		return -EIO;
+	}
+
+	ret = regmap_read(ak8974->map, AK8974_SELFTEST, &val);
+	if (ret)
+		return ret;
+	if (val != AK8974_SELFTEST_IDLE) {
+		dev_err(dev, "selftest not idle after test (%02x)\n", val);
+		return -EIO;
+	}
+	dev_dbg(dev, "passed self-test\n");
+
+	return 0;
+}
+
+static int ak8974_get_u16_val(struct ak8974 *ak8974, u8 reg, u16 *val)
+{
+	int ret;
+	u16 bulk;
+
+	ret = regmap_bulk_read(ak8974->map, reg, &bulk, 2);
+	if (ret)
+		return ret;
+	*val = le16_to_cpu(bulk);
+
+	return 0;
+}
+
+static int ak8974_detect(struct ak8974 *ak8974)
+{
+	unsigned int whoami;
+	const char *name;
+	int ret;
+	unsigned int fw;
+	u16 sn;
+
+	ret = regmap_read(ak8974->map, AK8974_WHOAMI, &whoami);
+	if (ret)
+		return ret;
+
+	switch (whoami) {
+	case AK8974_WHOAMI_VALUE_AMI305:
+		name = "ami305";
+		ret = regmap_read(ak8974->map, AMI305_VER, &fw);
+		if (ret)
+			return ret;
+		fw &= 0x7f; /* only bits 0 thru 6 valid */
+		ret = ak8974_get_u16_val(ak8974, AMI305_SN, &sn);
+		if (ret)
+			return ret;
+		dev_info(&ak8974->i2c->dev,
+			 "detected %s, FW ver %02x, S/N: %04x\n",
+			 name, fw, sn);
+		break;
+	case AK8974_WHOAMI_VALUE_AK8974:
+		name = "ak8974";
+		dev_info(&ak8974->i2c->dev, "detected AK8974\n");
+		break;
+	default:
+		dev_err(&ak8974->i2c->dev, "unsupported device (%02x) ",
+			whoami);
+		return -ENODEV;
+	}
+
+	ak8974->name = name;
+	ak8974->variant = whoami;
+
+	return 0;
+}
+
+static int ak8974_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2,
+			   long mask)
+{
+	struct ak8974 *ak8974 = iio_priv(indio_dev);
+	s16 hw_values[3];
+	int ret = -EINVAL;
+
+	pm_runtime_get_sync(&ak8974->i2c->dev);
+	mutex_lock(&ak8974->lock);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (chan->address > 2) {
+			dev_err(&ak8974->i2c->dev, "faulty channel address\n");
+			ret = -EIO;
+			goto out_unlock;
+		}
+		ret = ak8974_trigmeas(ak8974);
+		if (ret)
+			goto out_unlock;
+		ret = ak8974_getresult(ak8974, hw_values);
+		if (ret)
+			goto out_unlock;
+
+		/*
+		 * We read all axes and discard all but one, for optimized
+		 * reading, use the triggered buffer.
+		 */
+		*val = le16_to_cpu(hw_values[chan->address]);
+
+		ret = IIO_VAL_INT;
+	}
+
+ out_unlock:
+	mutex_unlock(&ak8974->lock);
+	pm_runtime_mark_last_busy(&ak8974->i2c->dev);
+	pm_runtime_put_autosuspend(&ak8974->i2c->dev);
+
+	return ret;
+}
+
+static void ak8974_fill_buffer(struct iio_dev *indio_dev)
+{
+	struct ak8974 *ak8974 = iio_priv(indio_dev);
+	int ret;
+	s16 hw_values[8]; /* Three axes + 64bit padding */
+
+	pm_runtime_get_sync(&ak8974->i2c->dev);
+	mutex_lock(&ak8974->lock);
+
+	ret = ak8974_trigmeas(ak8974);
+	if (ret) {
+		dev_err(&ak8974->i2c->dev, "error triggering measure\n");
+		goto out_unlock;
+	}
+	ret = ak8974_getresult(ak8974, hw_values);
+	if (ret) {
+		dev_err(&ak8974->i2c->dev, "error getting measures\n");
+		goto out_unlock;
+	}
+
+	iio_push_to_buffers_with_timestamp(indio_dev, hw_values,
+					   iio_get_time_ns(indio_dev));
+
+ out_unlock:
+	mutex_unlock(&ak8974->lock);
+	pm_runtime_mark_last_busy(&ak8974->i2c->dev);
+	pm_runtime_put_autosuspend(&ak8974->i2c->dev);
+}
+
+static irqreturn_t ak8974_handle_trigger(int irq, void *p)
+{
+	const struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+
+	ak8974_fill_buffer(indio_dev);
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static const struct iio_mount_matrix *
+ak8974_get_mount_matrix(const struct iio_dev *indio_dev,
+			const struct iio_chan_spec *chan)
+{
+	struct ak8974 *ak8974 = iio_priv(indio_dev);
+
+	return &ak8974->orientation;
+}
+
+static const struct iio_chan_spec_ext_info ak8974_ext_info[] = {
+	IIO_MOUNT_MATRIX(IIO_SHARED_BY_DIR, ak8974_get_mount_matrix),
+	{ },
+};
+
+#define AK8974_AXIS_CHANNEL(axis, index)				\
+	{								\
+		.type = IIO_MAGN,					\
+		.modified = 1,						\
+		.channel2 = IIO_MOD_##axis,				\
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+		.ext_info = ak8974_ext_info,				\
+		.address = index,					\
+		.scan_index = index,					\
+		.scan_type = {						\
+			.sign = 's',					\
+			.realbits = 16,					\
+			.storagebits = 16,				\
+			.endianness = IIO_LE				\
+		},							\
+	}
+
+static const struct iio_chan_spec ak8974_channels[] = {
+	AK8974_AXIS_CHANNEL(X, 0),
+	AK8974_AXIS_CHANNEL(Y, 1),
+	AK8974_AXIS_CHANNEL(Z, 2),
+	IIO_CHAN_SOFT_TIMESTAMP(3),
+};
+
+static const unsigned long ak8974_scan_masks[] = { 0x7, 0 };
+
+static const struct iio_info ak8974_info = {
+	.read_raw = &ak8974_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static bool ak8974_writeable_reg(struct device *dev, unsigned int reg)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct iio_dev *indio_dev = i2c_get_clientdata(i2c);
+	struct ak8974 *ak8974 = iio_priv(indio_dev);
+
+	switch (reg) {
+	case AK8974_CTRL1:
+	case AK8974_CTRL2:
+	case AK8974_CTRL3:
+	case AK8974_INT_CTRL:
+	case AK8974_INT_THRES:
+	case AK8974_INT_THRES + 1:
+	case AK8974_PRESET:
+	case AK8974_PRESET + 1:
+		return true;
+	case AK8974_OFFSET_X:
+	case AK8974_OFFSET_X + 1:
+	case AK8974_OFFSET_Y:
+	case AK8974_OFFSET_Y + 1:
+	case AK8974_OFFSET_Z:
+	case AK8974_OFFSET_Z + 1:
+		if (ak8974->variant == AK8974_WHOAMI_VALUE_AK8974)
+			return true;
+		return false;
+	case AMI305_OFFSET_X:
+	case AMI305_OFFSET_X + 1:
+	case AMI305_OFFSET_Y:
+	case AMI305_OFFSET_Y + 1:
+	case AMI305_OFFSET_Z:
+	case AMI305_OFFSET_Z + 1:
+		if (ak8974->variant == AK8974_WHOAMI_VALUE_AMI305)
+			return true;
+		return false;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config ak8974_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0xff,
+	.writeable_reg = ak8974_writeable_reg,
+};
+
+static int ak8974_probe(struct i2c_client *i2c,
+			const struct i2c_device_id *id)
+{
+	struct iio_dev *indio_dev;
+	struct ak8974 *ak8974;
+	unsigned long irq_trig;
+	int irq = i2c->irq;
+	int ret;
+
+	/* Register with IIO */
+	indio_dev = devm_iio_device_alloc(&i2c->dev, sizeof(*ak8974));
+	if (indio_dev == NULL)
+		return -ENOMEM;
+
+	ak8974 = iio_priv(indio_dev);
+	i2c_set_clientdata(i2c, indio_dev);
+	ak8974->i2c = i2c;
+	mutex_init(&ak8974->lock);
+
+	ret = of_iio_read_mount_matrix(&i2c->dev,
+				       "mount-matrix",
+				       &ak8974->orientation);
+	if (ret)
+		return ret;
+
+	ak8974->regs[0].supply = ak8974_reg_avdd;
+	ak8974->regs[1].supply = ak8974_reg_dvdd;
+
+	ret = devm_regulator_bulk_get(&i2c->dev,
+				      ARRAY_SIZE(ak8974->regs),
+				      ak8974->regs);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "cannot get regulators\n");
+		return ret;
+	}
+
+	ret = regulator_bulk_enable(ARRAY_SIZE(ak8974->regs), ak8974->regs);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "cannot enable regulators\n");
+		return ret;
+	}
+
+	/* Take runtime PM online */
+	pm_runtime_get_noresume(&i2c->dev);
+	pm_runtime_set_active(&i2c->dev);
+	pm_runtime_enable(&i2c->dev);
+
+	ak8974->map = devm_regmap_init_i2c(i2c, &ak8974_regmap_config);
+	if (IS_ERR(ak8974->map)) {
+		dev_err(&i2c->dev, "failed to allocate register map\n");
+		return PTR_ERR(ak8974->map);
+	}
+
+	ret = ak8974_set_power(ak8974, AK8974_PWR_ON);
+	if (ret) {
+		dev_err(&i2c->dev, "could not power on\n");
+		goto power_off;
+	}
+
+	ret = ak8974_detect(ak8974);
+	if (ret) {
+		dev_err(&i2c->dev, "neither AK8974 nor AMI305 found\n");
+		goto power_off;
+	}
+
+	ret = ak8974_selftest(ak8974);
+	if (ret)
+		dev_err(&i2c->dev, "selftest failed (continuing anyway)\n");
+
+	ret = ak8974_reset(ak8974);
+	if (ret) {
+		dev_err(&i2c->dev, "AK8974 reset failed\n");
+		goto power_off;
+	}
+
+	pm_runtime_set_autosuspend_delay(&i2c->dev,
+					 AK8974_AUTOSUSPEND_DELAY);
+	pm_runtime_use_autosuspend(&i2c->dev);
+	pm_runtime_put(&i2c->dev);
+
+	indio_dev->dev.parent = &i2c->dev;
+	indio_dev->channels = ak8974_channels;
+	indio_dev->num_channels = ARRAY_SIZE(ak8974_channels);
+	indio_dev->info = &ak8974_info;
+	indio_dev->available_scan_masks = ak8974_scan_masks;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->name = ak8974->name;
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+					 ak8974_handle_trigger,
+					 NULL);
+	if (ret) {
+		dev_err(&i2c->dev, "triggered buffer setup failed\n");
+		goto disable_pm;
+	}
+
+	/* If we have a valid DRDY IRQ, make use of it */
+	if (irq > 0) {
+		irq_trig = irqd_get_trigger_type(irq_get_irq_data(irq));
+		if (irq_trig == IRQF_TRIGGER_RISING) {
+			dev_info(&i2c->dev, "enable rising edge DRDY IRQ\n");
+		} else if (irq_trig == IRQF_TRIGGER_FALLING) {
+			ak8974->drdy_active_low = true;
+			dev_info(&i2c->dev, "enable falling edge DRDY IRQ\n");
+		} else {
+			irq_trig = IRQF_TRIGGER_RISING;
+		}
+		irq_trig |= IRQF_ONESHOT;
+		irq_trig |= IRQF_SHARED;
+
+		ret = devm_request_threaded_irq(&i2c->dev,
+						irq,
+						ak8974_drdy_irq,
+						ak8974_drdy_irq_thread,
+						irq_trig,
+						ak8974->name,
+						ak8974);
+		if (ret) {
+			dev_err(&i2c->dev, "unable to request DRDY IRQ "
+				"- proceeding without IRQ\n");
+			goto no_irq;
+		}
+		ak8974->drdy_irq = true;
+	}
+
+no_irq:
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(&i2c->dev, "device register failed\n");
+		goto cleanup_buffer;
+	}
+
+	return 0;
+
+cleanup_buffer:
+	iio_triggered_buffer_cleanup(indio_dev);
+disable_pm:
+	pm_runtime_put_noidle(&i2c->dev);
+	pm_runtime_disable(&i2c->dev);
+	ak8974_set_power(ak8974, AK8974_PWR_OFF);
+power_off:
+	regulator_bulk_disable(ARRAY_SIZE(ak8974->regs), ak8974->regs);
+
+	return ret;
+}
+
+static int __exit ak8974_remove(struct i2c_client *i2c)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(i2c);
+	struct ak8974 *ak8974 = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	iio_triggered_buffer_cleanup(indio_dev);
+	pm_runtime_get_sync(&i2c->dev);
+	pm_runtime_put_noidle(&i2c->dev);
+	pm_runtime_disable(&i2c->dev);
+	ak8974_set_power(ak8974, AK8974_PWR_OFF);
+	regulator_bulk_disable(ARRAY_SIZE(ak8974->regs), ak8974->regs);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int ak8974_runtime_suspend(struct device *dev)
+{
+	struct ak8974 *ak8974 =
+		iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
+
+	ak8974_set_power(ak8974, AK8974_PWR_OFF);
+	regulator_bulk_disable(ARRAY_SIZE(ak8974->regs), ak8974->regs);
+
+	return 0;
+}
+
+static int ak8974_runtime_resume(struct device *dev)
+{
+	struct ak8974 *ak8974 =
+		iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
+	int ret;
+
+	ret = regulator_bulk_enable(ARRAY_SIZE(ak8974->regs), ak8974->regs);
+	if (ret)
+		return ret;
+	msleep(AK8974_POWERON_DELAY);
+	ret = ak8974_set_power(ak8974, AK8974_PWR_ON);
+	if (ret)
+		goto out_regulator_disable;
+
+	ret = ak8974_configure(ak8974);
+	if (ret)
+		goto out_disable_power;
+
+	return 0;
+
+out_disable_power:
+	ak8974_set_power(ak8974, AK8974_PWR_OFF);
+out_regulator_disable:
+	regulator_bulk_disable(ARRAY_SIZE(ak8974->regs), ak8974->regs);
+
+	return ret;
+}
+#endif /* CONFIG_PM */
+
+static const struct dev_pm_ops ak8974_dev_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+	SET_RUNTIME_PM_OPS(ak8974_runtime_suspend,
+			   ak8974_runtime_resume, NULL)
+};
+
+static const struct i2c_device_id ak8974_id[] = {
+	{"ami305", 0 },
+	{"ak8974", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, ak8974_id);
+
+static const struct of_device_id ak8974_of_match[] = {
+	{ .compatible = "asahi-kasei,ak8974", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, ak8974_of_match);
+
+static struct i2c_driver ak8974_driver = {
+	.driver	 = {
+		.name	= "ak8974",
+		.owner	= THIS_MODULE,
+		.pm = &ak8974_dev_pm_ops,
+		.of_match_table = of_match_ptr(ak8974_of_match),
+	},
+	.probe	  = ak8974_probe,
+	.remove	  = __exit_p(ak8974_remove),
+	.id_table = ak8974_id,
+};
+module_i2c_driver(ak8974_driver);
+
+MODULE_DESCRIPTION("AK8974 and AMI305 3-axis magnetometer driver");
+MODULE_AUTHOR("Samu Onkalo");
+MODULE_AUTHOR("Linus Walleij");
+MODULE_LICENSE("GPL v2");