3 files changed, 29 insertions, 3 deletions

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
index b766c2218f4b..3dfd21f5d2a4 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
@@ -153,12 +153,14 @@ struct st_lsm6dsx_fifo_ops {
  * @hr_timer: Hw timer resolution register info (addr + mask).
  * @fifo_en: Hw timer FIFO enable register info (addr + mask).
  * @decimator: Hw timer FIFO decimator register info (addr + mask).
+ * @freq_fine: Difference in % of ODR with respect to the typical.
  */
 struct st_lsm6dsx_hw_ts_settings {
 	struct st_lsm6dsx_reg timer_en;
 	struct st_lsm6dsx_reg hr_timer;
 	struct st_lsm6dsx_reg fifo_en;
 	struct st_lsm6dsx_reg decimator;
+	u8 freq_fine;
 };
 
 /**
@@ -346,6 +348,7 @@ struct st_lsm6dsx_sensor {
  * @fifo_mode: FIFO operating mode supported by the device.
  * @suspend_mask: Suspended sensor bitmask.
  * @enable_mask: Enabled sensor bitmask.
+ * @ts_gain: Hw timestamp rate after internal calibration.
  * @ts_sip: Total number of timestamp samples in a given pattern.
  * @sip: Total number of samples (acc/gyro/ts) in a given pattern.
  * @buff: Device read buffer.
@@ -367,6 +370,7 @@ struct st_lsm6dsx_hw {
 	enum st_lsm6dsx_fifo_mode fifo_mode;
 	u8 suspend_mask;
 	u8 enable_mask;
+	s64 ts_gain;
 	u8 ts_sip;
 	u8 sip;
 
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
index 1f6873441aa0..ffeb2596b97b 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
@@ -50,7 +50,6 @@
 
 #define ST_LSM6DSX_MAX_FIFO_ODR_VAL		0x08
 
-#define ST_LSM6DSX_TS_SENSITIVITY		25000UL /* 25us */
 #define ST_LSM6DSX_TS_RESET_VAL			0xaa
 
 struct st_lsm6dsx_decimator_entry {
@@ -423,7 +422,7 @@ int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
 				 */
 				if (!reset_ts && ts >= 0xff0000)
 					reset_ts = true;
-				ts *= ST_LSM6DSX_TS_SENSITIVITY;
+				ts *= hw->ts_gain;
 
 				offset += ST_LSM6DSX_SAMPLE_SIZE;
 			}
@@ -572,7 +571,7 @@ int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw)
 				 */
 				if (!reset_ts && ts >= 0xffff0000)
 					reset_ts = true;
-				ts *= ST_LSM6DSX_TS_SENSITIVITY;
+				ts *= hw->ts_gain;
 			} else {
 				st_lsm6dsx_push_tagged_data(hw, tag, iio_buff,
 							    ts);
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
index 4f2a787f63f4..b0f525066237 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
@@ -63,6 +63,8 @@
 
 #define ST_LSM6DSX_REG_WHOAMI_ADDR		0x0f
 
+#define ST_LSM6DSX_TS_SENSITIVITY		25000UL /* 25us */
+
 static const struct iio_chan_spec st_lsm6dsx_acc_channels[] = {
 	ST_LSM6DSX_CHANNEL_ACC(IIO_ACCEL, 0x28, IIO_MOD_X, 0),
 	ST_LSM6DSX_CHANNEL_ACC(IIO_ACCEL, 0x2a, IIO_MOD_Y, 1),
@@ -843,6 +845,7 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
 				.addr = 0x0a,
 				.mask = GENMASK(7, 6),
 			},
+			.freq_fine = 0x63,
 		},
 		.shub_settings = {
 			.page_mux = {
@@ -1037,6 +1040,7 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
 				.addr = 0x0a,
 				.mask = GENMASK(7, 6),
 			},
+			.freq_fine = 0x63,
 		},
 		.event_settings = {
 			.enable_reg = {
@@ -1208,6 +1212,7 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
 				.addr = 0x0a,
 				.mask = GENMASK(7, 6),
 			},
+			.freq_fine = 0x63,
 		},
 		.shub_settings = {
 			.page_mux = {
@@ -1893,6 +1898,24 @@ static int st_lsm6dsx_init_hw_timer(struct st_lsm6dsx_hw *hw)
 		if (err < 0)
 			return err;
 	}
+
+	/* calibrate timestamp sensitivity */
+	hw->ts_gain = ST_LSM6DSX_TS_SENSITIVITY;
+	if (ts_settings->freq_fine) {
+		err = regmap_read(hw->regmap, ts_settings->freq_fine, &val);
+		if (err < 0)
+			return err;
+
+		/*
+		 * linearize the AN5192 formula:
+		 * 1 / (1 + x) ~= 1 - x (Taylor’s Series)
+		 * ttrim[s] = 1 / (40000 * (1 + 0.0015 * val))
+		 * ttrim[ns] ~= 25000 - 37.5 * val
+		 * ttrim[ns] ~= 25000 - (37500 * val) / 1000
+		 */
+		hw->ts_gain -= ((s8)val * 37500) / 1000;
+	}
+
 	return 0;
 }