iio: imu: inv_mpu6050: fix data polling interface

When reading data with the polling interface, we need to wait
at 1 sampling period to have a sample.
For gyroscope and magnetometer, we need to wait for 2 periods
before having a correct sample.

Not suitable for stable or backporting.
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

@@ -563,9 +563,14 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev,
 					 int *val)
 {
 	struct inv_mpu6050_state *st = iio_priv(indio_dev);
+	unsigned int freq_hz, period_us, min_sleep_us, max_sleep_us;
 	int result;
 	int ret;
 
+	/* compute sample period */
+	freq_hz = INV_MPU6050_DIVIDER_TO_FIFO_RATE(st->chip_config.divider);
+	period_us = 1000000 / freq_hz;
+
 	result = inv_mpu6050_set_power_itg(st, true);
 	if (result)
 		return result;
@@ -576,6 +581,10 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev,
 				INV_MPU6050_SENSOR_GYRO);
 		if (result)
 			goto error_power_off;
+		/* need to wait 2 periods to have first valid sample */
+		min_sleep_us = 2 * period_us;
+		max_sleep_us = 2 * (period_us + period_us / 2);
+		usleep_range(min_sleep_us, max_sleep_us);
 		ret = inv_mpu6050_sensor_show(st, st->reg->raw_gyro,
 					      chan->channel2, val);
 		result = inv_mpu6050_switch_engine(st, false,
@@ -588,6 +597,10 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev,
 				INV_MPU6050_SENSOR_ACCL);
 		if (result)
 			goto error_power_off;
+		/* wait 1 period for first sample availability */
+		min_sleep_us = period_us;
+		max_sleep_us = period_us + period_us / 2;
+		usleep_range(min_sleep_us, max_sleep_us);
 		ret = inv_mpu6050_sensor_show(st, st->reg->raw_accl,
 					      chan->channel2, val);
 		result = inv_mpu6050_switch_engine(st, false,
@@ -600,8 +613,10 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev,
 				INV_MPU6050_SENSOR_TEMP);
 		if (result)
 			goto error_power_off;
-		/* wait for stablization */
-		msleep(INV_MPU6050_TEMP_UP_TIME);
+		/* wait 1 period for first sample availability */
+		min_sleep_us = period_us;
+		max_sleep_us = period_us + period_us / 2;
+		usleep_range(min_sleep_us, max_sleep_us);
 		ret = inv_mpu6050_sensor_show(st, st->reg->temperature,
 					      IIO_MOD_X, val);
 		result = inv_mpu6050_switch_engine(st, false,
@@ -610,7 +625,24 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev,
 			goto error_power_off;
 		break;
 	case IIO_MAGN:
+		result = inv_mpu6050_switch_engine(st, true,
+				INV_MPU6050_SENSOR_MAGN);
+		if (result)
+			goto error_power_off;
+		/* frequency is limited for magnetometer */
+		if (freq_hz > INV_MPU_MAGN_FREQ_HZ_MAX) {
+			freq_hz = INV_MPU_MAGN_FREQ_HZ_MAX;
+			period_us = 1000000 / freq_hz;
+		}
+		/* need to wait 2 periods to have first valid sample */
+		min_sleep_us = 2 * period_us;
+		max_sleep_us = 2 * (period_us + period_us / 2);
+		usleep_range(min_sleep_us, max_sleep_us);
 		ret = inv_mpu_magn_read(st, chan->channel2, val);
+		result = inv_mpu6050_switch_engine(st, false,
+				INV_MPU6050_SENSOR_MAGN);
+		if (result)
+			goto error_power_off;
 		break;
 	default:
 		ret = -EINVAL;

drivers/iio/imu/inv_mpu6050/inv_mpu_magn.c

@@ -44,9 +44,6 @@
 #define INV_MPU_MAGN_REG_ASAY		0x11
 #define INV_MPU_MAGN_REG_ASAZ		0x12
 
-/* Magnetometer maximum frequency */
-#define INV_MPU_MAGN_FREQ_HZ_MAX	50
-
 static bool inv_magn_supported(const struct inv_mpu6050_state *st)
 {
 	switch (st->chip_type) {
@@ -321,7 +318,6 @@ int inv_mpu_magn_read(struct inv_mpu6050_state *st, int axis, int *val)
 	unsigned int status;
 	__be16 data;
 	uint8_t addr;
-	unsigned int freq_hz, period_ms;
 	int ret;
 
 	/* quit if chip is not supported */
@@ -344,23 +340,6 @@ int inv_mpu_magn_read(struct inv_mpu6050_state *st, int axis, int *val)
 	}
 	addr += INV_MPU6050_REG_EXT_SENS_DATA;
 
-	/* compute period depending on current sampling rate */
-	freq_hz = INV_MPU6050_DIVIDER_TO_FIFO_RATE(st->chip_config.divider);
-	if (freq_hz > INV_MPU_MAGN_FREQ_HZ_MAX)
-		freq_hz = INV_MPU_MAGN_FREQ_HZ_MAX;
-	period_ms = 1000 / freq_hz;
-
-	ret = inv_mpu6050_switch_engine(st, true, INV_MPU6050_SENSOR_MAGN);
-	if (ret)
-		return ret;
-
-	/* need to wait 2 periods + half-period margin */
-	msleep(period_ms * 2 + period_ms / 2);
-
-	ret = inv_mpu6050_switch_engine(st, false, INV_MPU6050_SENSOR_MAGN);
-	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)

drivers/iio/imu/inv_mpu6050/inv_mpu_magn.h

@@ -10,6 +10,9 @@
 
 #include "inv_mpu_iio.h"
 
+/* Magnetometer maximum frequency */
+#define INV_MPU_MAGN_FREQ_HZ_MAX	50
+
 int inv_mpu_magn_probe(struct inv_mpu6050_state *st);
 
 /**