iio: imu: inv_mpu6050: helpers for using i2c master on auxiliary bus

Add helper functions to use the i2c auxiliary bus with the MPU i2c
master block.

Support only register based chip, reading and 1 byte writing. These
will be useful for initializing magnetometers inside MPU9x50 chips.
Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/inv_mpu6050/Makefile

@@ -4,7 +4,8 @@
 #
 
 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-y := inv_mpu_core.o inv_mpu_ring.o inv_mpu_trigger.o \
+		 inv_mpu_aux.o
 
 obj-$(CONFIG_INV_MPU6050_I2C) += inv-mpu6050-i2c.o
 inv-mpu6050-i2c-y := inv_mpu_i2c.o inv_mpu_acpi.o

drivers/iio/imu/inv_mpu6050/inv_mpu_aux.c

+// 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 "inv_mpu_aux.h"
+#include "inv_mpu_iio.h"
+
+/*
+ * i2c master auxiliary bus transfer function.
+ * Requires the i2c operations to be correctly setup before.
+ */
+static int inv_mpu_i2c_master_xfer(const struct inv_mpu6050_state *st)
+{
+	/* use 50hz frequency for xfer */
+	const unsigned int freq = 50;
+	const unsigned int period_ms = 1000 / freq;
+	uint8_t d;
+	unsigned int user_ctrl;
+	int ret;
+
+	/* set sample rate */
+	d = INV_MPU6050_FIFO_RATE_TO_DIVIDER(freq);
+	ret = regmap_write(st->map, st->reg->sample_rate_div, d);
+	if (ret)
+		return ret;
+
+	/* start i2c master */
+	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)
+		goto error_restore_rate;
+
+	/* wait for xfer: 1 period + half-period margin */
+	msleep(period_ms + period_ms / 2);
+
+	/* stop i2c master */
+	user_ctrl = st->chip_config.user_ctrl;
+	ret = regmap_write(st->map, st->reg->user_ctrl, user_ctrl);
+	if (ret)
+		goto error_stop_i2c;
+
+	/* restore sample rate */
+	d = st->chip_config.divider;
+	ret = regmap_write(st->map, st->reg->sample_rate_div, d);
+	if (ret)
+		goto error_restore_rate;
+
+	return 0;
+
+error_stop_i2c:
+	regmap_write(st->map, st->reg->user_ctrl, st->chip_config.user_ctrl);
+error_restore_rate:
+	regmap_write(st->map, st->reg->sample_rate_div, st->chip_config.divider);
+	return ret;
+}
+
+/**
+ * inv_mpu_aux_init() - init i2c auxiliary bus
+ * @st: driver internal state
+ *
+ * Returns 0 on success, a negative error code otherwise.
+ */
+int inv_mpu_aux_init(const struct inv_mpu6050_state *st)
+{
+	unsigned int val;
+	int ret;
+
+	/* configure i2c master */
+	val = INV_MPU6050_BITS_I2C_MST_CLK_400KHZ |
+			INV_MPU6050_BIT_WAIT_FOR_ES;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_MST_CTRL, val);
+	if (ret)
+		return ret;
+
+	/* configure i2c master delay */
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV4_CTRL, 0);
+	if (ret)
+		return ret;
+
+	val = INV_MPU6050_BIT_I2C_SLV0_DLY_EN |
+			INV_MPU6050_BIT_I2C_SLV1_DLY_EN |
+			INV_MPU6050_BIT_I2C_SLV2_DLY_EN |
+			INV_MPU6050_BIT_I2C_SLV3_DLY_EN |
+			INV_MPU6050_BIT_DELAY_ES_SHADOW;
+	return regmap_write(st->map, INV_MPU6050_REG_I2C_MST_DELAY_CTRL, val);
+}
+
+/**
+ * inv_mpu_aux_read() - read register function for i2c auxiliary bus
+ * @st: driver internal state.
+ * @addr: chip i2c Address
+ * @reg: chip register address
+ * @val: buffer for storing read bytes
+ * @size: number of bytes to read
+ *
+ *  Returns 0 on success, a negative error code otherwise.
+ */
+int inv_mpu_aux_read(const struct inv_mpu6050_state *st, uint8_t addr,
+		     uint8_t reg, uint8_t *val, size_t size)
+{
+	unsigned int status;
+	int ret;
+
+	if (size > 0x0F)
+		return -EINVAL;
+
+	/* setup i2c SLV0 control: i2c addr, register, enable + size */
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_ADDR(0),
+			   INV_MPU6050_BIT_I2C_SLV_RNW | addr);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_REG(0), reg);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(0),
+			   INV_MPU6050_BIT_SLV_EN | size);
+	if (ret)
+		return ret;
+
+	/* do i2c xfer */
+	ret = inv_mpu_i2c_master_xfer(st);
+	if (ret)
+		goto error_disable_i2c;
+
+	/* disable i2c slave */
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(0), 0);
+	if (ret)
+		goto error_disable_i2c;
+
+	/* check i2c status */
+	ret = regmap_read(st->map, INV_MPU6050_REG_I2C_MST_STATUS, &status);
+	if (ret)
+		return ret;
+	if (status & INV_MPU6050_BIT_I2C_SLV0_NACK)
+		return -EIO;
+
+	/* read data in registers */
+	return regmap_bulk_read(st->map, INV_MPU6050_REG_EXT_SENS_DATA,
+				val, size);
+
+error_disable_i2c:
+	regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(0), 0);
+	return ret;
+}
+
+/**
+ * inv_mpu_aux_write() - write register function for i2c auxiliary bus
+ * @st: driver internal state.
+ * @addr: chip i2c Address
+ * @reg: chip register address
+ * @val: 1 byte value to write
+ *
+ *  Returns 0 on success, a negative error code otherwise.
+ */
+int inv_mpu_aux_write(const struct inv_mpu6050_state *st, uint8_t addr,
+		      uint8_t reg, uint8_t val)
+{
+	unsigned int status;
+	int ret;
+
+	/* setup i2c SLV0 control: i2c addr, register, value, enable + size */
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_ADDR(0), addr);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_REG(0), reg);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_DO(0), val);
+	if (ret)
+		return ret;
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(0),
+			   INV_MPU6050_BIT_SLV_EN | 1);
+	if (ret)
+		return ret;
+
+	/* do i2c xfer */
+	ret = inv_mpu_i2c_master_xfer(st);
+	if (ret)
+		goto error_disable_i2c;
+
+	/* disable i2c slave */
+	ret = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(0), 0);
+	if (ret)
+		goto error_disable_i2c;
+
+	/* check i2c status */
+	ret = regmap_read(st->map, INV_MPU6050_REG_I2C_MST_STATUS, &status);
+	if (ret)
+		return ret;
+	if (status & INV_MPU6050_BIT_I2C_SLV0_NACK)
+		return -EIO;
+
+	return 0;
+
+error_disable_i2c:
+	regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(0), 0);
+	return ret;
+}

drivers/iio/imu/inv_mpu6050/inv_mpu_aux.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 TDK-InvenSense, Inc.
+ */
+
+#ifndef INV_MPU_AUX_H_
+#define INV_MPU_AUX_H_
+
+#include "inv_mpu_iio.h"
+
+int inv_mpu_aux_init(const struct inv_mpu6050_state *st);
+
+int inv_mpu_aux_read(const struct inv_mpu6050_state *st, uint8_t addr,
+		     uint8_t reg, uint8_t *val, size_t size);
+
+int inv_mpu_aux_write(const struct inv_mpu6050_state *st, uint8_t addr,
+		      uint8_t reg, uint8_t val);
+
+#endif		/* INV_MPU_AUX_H_ */