iio: imu: inv_mpu6050: add all signal path resets at init

Old chips using spi require for a full reset to manually reset
all signal path. This does not harm when using i2c so do it
inconditionally. Exclude i2c only chips.
Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c

@@ -1146,6 +1146,24 @@ static int inv_check_and_setup_chip(struct inv_mpu6050_state *st)
 	if (result)
 		return result;
 	msleep(INV_MPU6050_POWER_UP_TIME);
+	switch (st->chip_type) {
+	case INV_MPU6000:
+	case INV_MPU6500:
+	case INV_MPU6515:
+	case INV_MPU9250:
+	case INV_MPU9255:
+		/* reset signal path (required for spi connection) */
+		regval = INV_MPU6050_BIT_TEMP_RST | INV_MPU6050_BIT_ACCEL_RST |
+			 INV_MPU6050_BIT_GYRO_RST;
+		result = regmap_write(st->map, INV_MPU6050_REG_SIGNAL_PATH_RESET,
+				      regval);
+		if (result)
+			return result;
+		msleep(INV_MPU6050_POWER_UP_TIME);
+		break;
+	default:
+		break;
+	}
 
 	/*
 	 * Turn power on. After reset, the sleep bit could be on

drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h

@@ -245,7 +245,13 @@ struct inv_mpu6050_state {
 #define INV_MPU6050_BIT_I2C_SLV3_DLY_EN     0x08
 #define INV_MPU6050_BIT_DELAY_ES_SHADOW     0x80
 
+#define INV_MPU6050_REG_SIGNAL_PATH_RESET   0x68
+#define INV_MPU6050_BIT_TEMP_RST            BIT(0)
+#define INV_MPU6050_BIT_ACCEL_RST           BIT(1)
+#define INV_MPU6050_BIT_GYRO_RST            BIT(2)
+
 #define INV_MPU6050_REG_USER_CTRL           0x6A
+#define INV_MPU6050_BIT_SIG_COND_RST        0x01
 #define INV_MPU6050_BIT_FIFO_RST            0x04
 #define INV_MPU6050_BIT_DMP_RST             0x08
 #define INV_MPU6050_BIT_I2C_MST_EN          0x20