[PATCH 6/8] iio: imu: inv_mpu6050: add magnetometer implementation for MPU925x

[Jean-Baptiste Maneyrol <JManeyrol@invensense.com>]

Add implementation for driving MPU9250 magnetometer connected on
i2c auxiliary bus using the MPU i2c master. This is currently not
wired inside the main mpu driver.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
---
 drivers/iio/imu/inv_mpu6050/Makefile          |   2 +-
 .../iio/imu/inv_mpu6050/inv_mpu9250_magn.c    | 239 ++++++++++++++++++
 .../iio/imu/inv_mpu6050/inv_mpu9250_magn.h    |  27 ++
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h     |   4 +
 4 files changed, 271 insertions(+), 1 deletion(-)
 create mode 100644 drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.c
 create mode 100644 drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.h

diff --git a/drivers/iio/imu/inv_mpu6050/Makefile b/drivers/iio/imu/inv_mpu6050/Makefile
index 187f003c81f2..fee41415ebdb 100644
--- a/drivers/iio/imu/inv_mpu6050/Makefile
+++ b/drivers/iio/imu/inv_mpu6050/Makefile
@@ -5,7 +5,7 @@
 
 obj-$(CONFIG_INV_MPU6050_IIO) += inv-mpu6050.o
 inv-mpu6050-y := inv_mpu_core.o inv_mpu_ring.o inv_mpu_trigger.o
-inv-mpu6050-$(CONFIG_INV_MPU6050_MAGN) += inv_mpu_aux.o
+inv-mpu6050-$(CONFIG_INV_MPU6050_MAGN) += inv_mpu_aux.o inv_mpu9250_magn.o
 
 obj-$(CONFIG_INV_MPU6050_I2C) += inv-mpu6050-i2c.o
 inv-mpu6050-i2c-y := inv_mpu_i2c.o inv_mpu_acpi.o
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.c b/drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.c
new file mode 100644
index 000000000000..0c2230247557
--- /dev/null
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 TDK-InvenSense, Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/regmap.h>
+#include <linux/delay.h>
+#include <linux/string.h>
+#include <asm/unaligned.h>
+
+#include "inv_mpu_iio.h"
+#include "inv_mpu_aux.h"
+#include "inv_mpu9250_magn.h"
+
+/*
+ * MPU9250 magnetometer is an AKM AK8963 chip on I2C aux bus
+ */
+#define INV_MPU9250_MAGN_I2C_ADDR		0x0C
+
+#define INV_MPU9250_MAGN_REG_WIA		0x00
+#define INV_MPU9250_MAGN_BITS_WIA		0x48
+
+#define INV_MPU9250_MAGN_REG_ST1		0x02
+#define INV_MPU9250_MAGN_BIT_DRDY		0x01
+#define INV_MPU9250_MAGN_BIT_DOR		0x02
+
+#define INV_MPU9250_MAGN_REG_DATA		0x03
+
+#define INV_MPU9250_MAGN_REG_ST2		0x09
+#define INV_MPU9250_MAGN_BIT_HOFL		0x08
+#define INV_MPU9250_MAGN_BIT_BITM		0x10
+
+#define INV_MPU9250_MAGN_REG_CNTL1		0x0A
+#define INV_MPU9250_MAGN_BITS_MODE_PWDN		0x00
+#define INV_MPU9250_MAGN_BITS_MODE_SINGLE	0x01
+#define INV_MPU9250_MAGN_BITS_MODE_FUSE		0x0F
+#define INV_MPU9250_MAGN_BIT_OUTPUT_BIT		0x10
+
+#define INV_MPU9250_MAGN_REG_CNTL2		0x0B
+#define INV_MPU9250_MAGN_BIT_SRST		0x01
+
+#define INV_MPU9250_MAGN_REG_ASAX		0x10
+#define INV_MPU9250_MAGN_REG_ASAY		0x11
+#define INV_MPU9250_MAGN_REG_ASAZ		0x12
+
+/* init magnetometer chip */
+static int inv_magn_init(struct inv_mpu6050_state *st)
+{
+	uint8_t val;
+	uint8_t asa[3];
+	int ret;
+
+	/* check whoami */
+	ret = inv_mpu_aux_read(st, INV_MPU9250_MAGN_I2C_ADDR,
+			       INV_MPU9250_MAGN_REG_WIA, &val, sizeof(val));
+	if (ret)
+		return ret;
+	if (val != INV_MPU9250_MAGN_BITS_WIA)
+		return -ENODEV;
+
+	/* reset chip */
+	ret = inv_mpu_aux_write(st, INV_MPU9250_MAGN_I2C_ADDR,
+				INV_MPU9250_MAGN_REG_CNTL2,
+				INV_MPU9250_MAGN_BIT_SRST);
+	if (ret)
+		return ret;
+
+	/* read fuse ROM data */
+	ret = inv_mpu_aux_write(st, INV_MPU9250_MAGN_I2C_ADDR,
+				INV_MPU9250_MAGN_REG_CNTL1,
+				INV_MPU9250_MAGN_BITS_MODE_FUSE);
+	if (ret)
+		return ret;
+	ret = inv_mpu_aux_read(st, INV_MPU9250_MAGN_I2C_ADDR,
+			       INV_MPU9250_MAGN_REG_ASAX, asa, sizeof(asa));
+	if (ret)
+		return ret;
+
+	/* switch back to power-down */
+	ret = inv_mpu_aux_write(st, INV_MPU9250_MAGN_I2C_ADDR,
+				INV_MPU9250_MAGN_REG_CNTL1,
+				INV_MPU9250_MAGN_BITS_MODE_PWDN);
+	if (ret)
+		return ret;
+
+	/*
+	 * Sensitivity adjustement and scale to Gauss
+	 *
+	 * Hadj = H * (((ASA - 128) * 0.5 / 128) + 1)
+	 * Factor simplification:
+	 * Hadj = H * ((ASA + 128) / 256)
+	 *
+	 * sensor sensitivity: 0.15 uT (16 bits)
+	 * 1 uT = 0.01 G and value is in micron (1e6)
+	 *
+	 * Hadj = H * ((ASA + 128) / 256) * 0.15 * 0.01 * 1e6
+	 * Hadj = H * ((ASA + 128) / 256) * 1500
+	 */
+	st->magn_raw_to_gauss[0] = (((int32_t)asa[0] + 128) * 1500) / 256;
+	st->magn_raw_to_gauss[1] = (((int32_t)asa[1] + 128) * 1500) / 256;
+	st->magn_raw_to_gauss[2] = (((int32_t)asa[2] + 128) * 1500) / 256;
+
+	return 0;
+}
+
+/**
+ * Probe magnetometer chip and setup all i2c transfers.
+ * SLV0: read sensor data
+ * SLV1: launch sensor single measurement
+ *
+ * Sampling data requires 2 cycles to read after measurement.
+ * A measurement can take up to ~10ms.
+ */
+int inv_mpu9250_magn_probe(struct inv_mpu6050_state *st)
+{
+	int ret;
+
+	/* check and init mag chip */
+	ret = inv_magn_init(st);
+	if (ret)
+		return ret;
+
+	/*
+	 * configure mpu i2c master accesses
+	 * i2c SLV0: read sensor data, 7 bytes data(6)-ST2
+	 * Byte swap data to store them in big-endian in impair address groups
+	 */
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_ADDR(0),
+			   INV_MPU6050_BIT_I2C_SLV_RNW |
+			   INV_MPU9250_MAGN_I2C_ADDR);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_REG(0),
+			   INV_MPU9250_MAGN_REG_DATA);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(0),
+			   INV_MPU6050_BIT_SLV_EN |
+			   INV_MPU6050_BIT_SLV_BYTE_SW |
+			   INV_MPU6050_BIT_SLV_GRP |
+			   INV_MPU9X50_BYTES_MAGN);
+	if (ret)
+		return ret;
+
+	/* i2c SLV1: launch single measurement */
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_ADDR(1),
+			   INV_MPU9250_MAGN_I2C_ADDR);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_REG(1),
+			   INV_MPU9250_MAGN_REG_CNTL1);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_DO(1),
+			   INV_MPU9250_MAGN_BITS_MODE_SINGLE |
+			   INV_MPU9250_MAGN_BIT_OUTPUT_BIT);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(1),
+			   INV_MPU6050_BIT_SLV_EN | 1);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/**
+ * Read magnetometer data from MPU fifo.
+ * Sampling data requires running the i2c master for 2 cycles.
+ * Use magnetometer maximal supported frequency.
+ */
+int inv_mpu9250_magn_read(const struct inv_mpu6050_state *st, int axis,
+			  int *val)
+{
+	unsigned int user_ctrl, status;
+	__be16 data[3];
+	uint8_t addr;
+	uint8_t d;
+	unsigned int period_ms;
+	int ret;
+
+	/* Mag data: X - Y - Z */
+	switch (axis) {
+	case IIO_MOD_X:
+		addr = 0;
+		break;
+	case IIO_MOD_Y:
+		addr = 1;
+		break;
+	case IIO_MOD_Z:
+		addr = 2;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* set sample rate to max mag freq */
+	d = INV_MPU6050_FIFO_RATE_TO_DIVIDER(INV_MPU9250_MAGN_FREQ_HZ_MAX);
+	ret = regmap_write(st->map, st->reg->sample_rate_div, d);
+	if (ret)
+		return ret;
+
+	/* start i2c master, wait for xfer, stop */
+	user_ctrl = st->chip_config.user_ctrl | INV_MPU6050_BIT_I2C_MST_EN;
+	ret = regmap_write(st->map, st->reg->user_ctrl, user_ctrl);
+	if (ret)
+		return ret;
+	/* need to wait 2 periods + half-period margin */
+	period_ms = 1000 / INV_MPU9250_MAGN_FREQ_HZ_MAX;
+	msleep(period_ms * 2 + period_ms / 2);
+	user_ctrl = st->chip_config.user_ctrl;
+	ret = regmap_write(st->map, st->reg->user_ctrl, user_ctrl);
+	if (ret)
+		return ret;
+
+	/* restore sample rate */
+	d = st->chip_config.divider;
+	ret = regmap_write(st->map, st->reg->sample_rate_div, d);
+	if (ret)
+		return ret;
+
+	/* check i2c status and read raw data */
+	ret = regmap_read(st->map, INV_MPU6050_REG_I2C_MST_STATUS, &status);
+	if (ret)
+		return ret;
+	if (status & INV_MPU6050_BIT_I2C_SLV0_NACK ||
+			status & INV_MPU6050_BIT_I2C_SLV1_NACK)
+		return -EIO;
+	ret = regmap_bulk_read(st->map, INV_MPU6050_REG_EXT_SENS_DATA,
+			       data, sizeof(data));
+	if (ret)
+		return ret;
+
+	*val = (int16_t)be16_to_cpu(data[addr]);
+
+	return IIO_VAL_INT;
+}
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.h b/drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.h
new file mode 100644
index 000000000000..9899dd6c560c
--- /dev/null
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu9250_magn.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 TDK-InvenSense, Inc.
+ */
+
+#ifndef INV_MPU9250_MAGN_H_
+#define INV_MPU9250_MAGN_H_
+
+#include <linux/kernel.h>
+
+#include "inv_mpu_iio.h"
+
+/* Magnetometer maximum frequency */
+#define INV_MPU9250_MAGN_FREQ_HZ_MAX		50
+
+/**
+ * inv_mpu9250_magn_probe() - MPU9250 implementation
+ */
+int inv_mpu9250_magn_probe(struct inv_mpu6050_state *st);
+
+/**
+ * inv_mpu9250_magn_read() - MPU9250 implementation
+ */
+int inv_mpu9250_magn_read(const struct inv_mpu6050_state *st, int axis,
+			  int *val);
+
+#endif
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
index 82669ecb4735..5b462672bbcb 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
@@ -129,6 +129,7 @@ struct inv_mpu6050_hw {
  *  @it_timestamp:	timestamp from previous interrupt.
  *  @data_timestamp:	timestamp for next data sample.
  *  @vddio_supply	voltage regulator for the chip.
+ *  @magn_raw_to_gauss:	coefficient to convert mag raw value to Gauss.
  */
 struct inv_mpu6050_state {
 	struct mutex lock;
@@ -150,6 +151,9 @@ struct inv_mpu6050_state {
 	s64 it_timestamp;
 	s64 data_timestamp;
 	struct regulator *vddio_supply;
+#ifdef CONFIG_INV_MPU6050_MAGN
+	s32 magn_raw_to_gauss[3];
+#endif
 };
 
 /*register and associated bit definition*/
-- 
2.17.1