drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h | 18 ++++++++++++++++++ drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 19 ++++++++----------- 2 files changed, 26 insertions(+), 11 deletions(-)
The calibrated timestamp is calculated from the nominal value using the
formula:
ts_gain[ns] ≈ ts_sensitivity - (ts_trim_coeff * val) / 1000.
The values of ts_sensitivity and ts_trim_coeff are not the same for all
devices, so it is necessary to differentiate them based on the part name.
For the correct values please consult the relevant AN.
Signed-off-by: Mario Tesi <mario.tesi@st.com>
---
drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h | 18 ++++++++++++++++++
drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 19 ++++++++-----------
2 files changed, 26 insertions(+), 11 deletions(-)
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
index c225b246c8a5..f8486a1b02d0 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
@@ -192,6 +192,22 @@ struct st_lsm6dsx_fifo_ops {
* @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.
+ * @ts_sensitivity: Nominal timestamp sensitivity.
+ * @ts_trim_coeff: Coefficient for calculating the calibrated timestamp gain.
+ * This coefficient comes into play when linearizing the formula
+ * used to calculate the calibrated timestamp (please see the
+ * relevant formula in the AN for the specific IMU).
+ * For example, in the case of LSM6DSO we have:
+ *
+ * 1 / (1 + x) ~= 1 - x (Taylor’s Series)
+ * ttrim[s] = 1 / (40000 * (1 + 0.0015 * val)) (from AN5192)
+ * ttrim[ns] ~= 25000 - 37.5 * val
+ * ttrim[ns] ~= 25000 - (37500 * val) / 1000
+ *
+ * so, replacing ts_sensitivity = 25000 and
+ * ts_trim_coeff = 37500
+ *
+ * ttrim[ns] ~= ts_sensitivity - (ts_trim_coeff * val) / 1000
*/
struct st_lsm6dsx_hw_ts_settings {
struct st_lsm6dsx_reg timer_en;
@@ -199,6 +215,8 @@ struct st_lsm6dsx_hw_ts_settings {
struct st_lsm6dsx_reg fifo_en;
struct st_lsm6dsx_reg decimator;
u8 freq_fine;
+ u16 ts_sensitivity;
+ u16 ts_trim_coeff;
};
/**
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
index d8cb4b0218d5..a2daf0c14d96 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
@@ -94,8 +94,6 @@
#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),
@@ -983,6 +981,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
.mask = GENMASK(7, 6),
},
.freq_fine = 0x63,
+ .ts_sensitivity = 25000,
+ .ts_trim_coeff = 37500,
},
.shub_settings = {
.page_mux = {
@@ -1196,6 +1196,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
.mask = GENMASK(7, 6),
},
.freq_fine = 0x63,
+ .ts_sensitivity = 25000,
+ .ts_trim_coeff = 37500,
},
.event_settings = {
.enable_reg = {
@@ -1371,6 +1373,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
.mask = GENMASK(7, 6),
},
.freq_fine = 0x4f,
+ .ts_sensitivity = 21701,
+ .ts_trim_coeff = 28212,
},
.shub_settings = {
.page_mux = {
@@ -2248,20 +2252,13 @@ static int st_lsm6dsx_init_hw_timer(struct st_lsm6dsx_hw *hw)
}
/* calibrate timestamp sensitivity */
- hw->ts_gain = ST_LSM6DSX_TS_SENSITIVITY;
+ hw->ts_gain = ts_settings->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;
+ hw->ts_gain -= ((s8)val * ts_settings->ts_trim_coeff) / 1000;
}
return 0;
--
2.25.1
> The calibrated timestamp is calculated from the nominal value using the
> formula:
> ts_gain[ns] ≈ ts_sensitivity - (ts_trim_coeff * val) / 1000.
>
> The values of ts_sensitivity and ts_trim_coeff are not the same for all
> devices, so it is necessary to differentiate them based on the part name.
> For the correct values please consult the relevant AN.
>
> Signed-off-by: Mario Tesi <mario.tesi@st.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
> drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h | 18 ++++++++++++++++++
> drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 19 ++++++++-----------
> 2 files changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> index c225b246c8a5..f8486a1b02d0 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> @@ -192,6 +192,22 @@ struct st_lsm6dsx_fifo_ops {
> * @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.
> + * @ts_sensitivity: Nominal timestamp sensitivity.
> + * @ts_trim_coeff: Coefficient for calculating the calibrated timestamp gain.
> + * This coefficient comes into play when linearizing the formula
> + * used to calculate the calibrated timestamp (please see the
> + * relevant formula in the AN for the specific IMU).
> + * For example, in the case of LSM6DSO we have:
> + *
> + * 1 / (1 + x) ~= 1 - x (Taylor’s Series)
> + * ttrim[s] = 1 / (40000 * (1 + 0.0015 * val)) (from AN5192)
> + * ttrim[ns] ~= 25000 - 37.5 * val
> + * ttrim[ns] ~= 25000 - (37500 * val) / 1000
> + *
> + * so, replacing ts_sensitivity = 25000 and
> + * ts_trim_coeff = 37500
> + *
> + * ttrim[ns] ~= ts_sensitivity - (ts_trim_coeff * val) / 1000
> */
> struct st_lsm6dsx_hw_ts_settings {
> struct st_lsm6dsx_reg timer_en;
> @@ -199,6 +215,8 @@ struct st_lsm6dsx_hw_ts_settings {
> struct st_lsm6dsx_reg fifo_en;
> struct st_lsm6dsx_reg decimator;
> u8 freq_fine;
> + u16 ts_sensitivity;
> + u16 ts_trim_coeff;
> };
>
> /**
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> index d8cb4b0218d5..a2daf0c14d96 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> @@ -94,8 +94,6 @@
>
> #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),
> @@ -983,6 +981,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
> .mask = GENMASK(7, 6),
> },
> .freq_fine = 0x63,
> + .ts_sensitivity = 25000,
> + .ts_trim_coeff = 37500,
> },
> .shub_settings = {
> .page_mux = {
> @@ -1196,6 +1196,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
> .mask = GENMASK(7, 6),
> },
> .freq_fine = 0x63,
> + .ts_sensitivity = 25000,
> + .ts_trim_coeff = 37500,
> },
> .event_settings = {
> .enable_reg = {
> @@ -1371,6 +1373,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
> .mask = GENMASK(7, 6),
> },
> .freq_fine = 0x4f,
> + .ts_sensitivity = 21701,
> + .ts_trim_coeff = 28212,
> },
> .shub_settings = {
> .page_mux = {
> @@ -2248,20 +2252,13 @@ static int st_lsm6dsx_init_hw_timer(struct st_lsm6dsx_hw *hw)
> }
>
> /* calibrate timestamp sensitivity */
> - hw->ts_gain = ST_LSM6DSX_TS_SENSITIVITY;
> + hw->ts_gain = ts_settings->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;
> + hw->ts_gain -= ((s8)val * ts_settings->ts_trim_coeff) / 1000;
> }
>
> return 0;
> --
> 2.25.1
>
On Wed, 15 Oct 2025 19:50:16 +0200 Lorenzo Bianconi <lorenzo@kernel.org> wrote: > > The calibrated timestamp is calculated from the nominal value using the > > formula: > > ts_gain[ns] ≈ ts_sensitivity - (ts_trim_coeff * val) / 1000. > > > > The values of ts_sensitivity and ts_trim_coeff are not the same for all > > devices, so it is necessary to differentiate them based on the part name. > > For the correct values please consult the relevant AN. > > > > Signed-off-by: Mario Tesi <mario.tesi@st.com> > > Acked-by: Lorenzo Bianconi <lorenzo@kernel.org> Fixes tag? Just reply to this thread with one and I'll pick it up from here. No need for a new version. Otherwise seems fine to me. Thanks, Jonathan
On Sat, Oct 18, 2025 at 08:23:01PM +0100, Jonathan Cameron wrote:
> On Wed, 15 Oct 2025 19:50:16 +0200
> Lorenzo Bianconi <lorenzo@kernel.org> wrote:
>
> > > The calibrated timestamp is calculated from the nominal value using the
> > > formula:
> > > ts_gain[ns] ≈ ts_sensitivity - (ts_trim_coeff * val) / 1000.
> > >
> > > The values of ts_sensitivity and ts_trim_coeff are not the same for all
> > > devices, so it is necessary to differentiate them based on the part name.
> > > For the correct values please consult the relevant AN.
> > >
> > > Signed-off-by: Mario Tesi <mario.tesi@st.com>
> >
> > Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
>
> Fixes tag? Just reply to this thread with one and I'll pick it up from here.
> No need for a new version.
>
> Otherwise seems fine to me.
>
> Thanks,
>
> Jonathan
>
Fixes: cb3b6b8e1bc0 ("iio: imu: st_lsm6dsx: add odr calibration feature")
Thanks,
Mario
On Tue, 21 Oct 2025 13:35:44 +0200
Mario Tesi <martepisa@gmail.com> wrote:
> On Sat, Oct 18, 2025 at 08:23:01PM +0100, Jonathan Cameron wrote:
> > On Wed, 15 Oct 2025 19:50:16 +0200
> > Lorenzo Bianconi <lorenzo@kernel.org> wrote:
> >
> > > > The calibrated timestamp is calculated from the nominal value using the
> > > > formula:
> > > > ts_gain[ns] ≈ ts_sensitivity - (ts_trim_coeff * val) / 1000.
> > > >
> > > > The values of ts_sensitivity and ts_trim_coeff are not the same for all
> > > > devices, so it is necessary to differentiate them based on the part name.
> > > > For the correct values please consult the relevant AN.
> > > >
> > > > Signed-off-by: Mario Tesi <mario.tesi@st.com>
> > >
> > > Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
> >
> > Fixes tag? Just reply to this thread with one and I'll pick it up from here.
> > No need for a new version.
> >
> > Otherwise seems fine to me.
> >
> > Thanks,
> >
> > Jonathan
> >
> Fixes: cb3b6b8e1bc0 ("iio: imu: st_lsm6dsx: add odr calibration feature")
>
Thanks. Applied to the fixes-togreg branch of iio.git.
I might hold this back if I get so far as doing a pull request today or
tomorrow just to give it a little time to soak in linux-next.
Thanks,
Jonathan
> Thanks,
> Mario
>
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