[PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value

[PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value

[Jean-Baptiste Maneyrol via B4 Relay]

From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Clock period value is used for computing periods of sampling. There is
no need for it to be higher than the maximum odr, otherwise we are
losing precision in the computation for nothing.

Switch clock period value to maximum odr period (8kHz).

Fixes: 0ecc363ccea7 ("iio: make invensense timestamp module generic")
Cc: stable@vger.kernel.org
Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
---
 drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c | 4 ++--
 drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c  | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
index 532d5fdffaf8..7df920ef3cf0 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
@@ -1170,10 +1170,10 @@ struct iio_dev *inv_icm42600_accel_init(struct inv_icm42600_state *st)
 	accel_st->filter = INV_ICM42600_FILTER_AVG_16X;
 
 	/*
-	 * clock period is 32kHz (31250ns)
+	 * clock period is 8kHz (125000ns)
 	 * jitter is +/- 2% (20 per mille)
 	 */
-	ts_chip.clock_period = 31250;
+	ts_chip.clock_period = 125000;
 	ts_chip.jitter = 20;
 	ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
 	inv_sensors_timestamp_init(&accel_st->ts, &ts_chip);
diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
index 11339ddf1da3..a18dcac93929 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
@@ -755,10 +755,10 @@ struct iio_dev *inv_icm42600_gyro_init(struct inv_icm42600_state *st)
 	}
 
 	/*
-	 * clock period is 32kHz (31250ns)
+	 * clock period is 8kHz (125000ns)
 	 * jitter is +/- 2% (20 per mille)
 	 */
-	ts_chip.clock_period = 31250;
+	ts_chip.clock_period = 125000;
 	ts_chip.jitter = 20;
 	ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
 	inv_sensors_timestamp_init(&gyro_st->ts, &ts_chip);

---
base-commit: cc746297b23e89bd5df9f91f3a0ca209e8991763
change-id: 20260623-inv-icm42600-fix-timestamp-clock-period-931338a848c3

Best regards,
--  
Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Re: [PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value

[Jean-Baptiste Maneyrol]

>From: Jean-Baptiste Maneyrol via B4 Relay <devnull+jean-baptiste.maneyrol.tdk.com@kernel.org>
>Sent: Tuesday, June 23, 2026 16:22
>To: Jonathan Cameron; David Lechner; Nuno Sá; Andy Shevchenko
>Cc: linux-iio@vger.kernel.org; linux-kernel@vger.kernel.org; Jonathan Cameron; stable@vger.kernel.org; Jean-Baptiste Maneyrol
>Subject: [PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value
>
>From: Jean-Baptiste Maneyrol <jean-baptiste. maneyrol@ tdk. com> Clock period value is used for computing periods of sampling. There is no need for it to be higher than the maximum odr, otherwise we are losing precision in the computation
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>From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
>
>Clock period value is used for computing periods of sampling. There is
>no need for it to be higher than the maximum odr, otherwise we are
>losing precision in the computation for nothing.
>
>Switch clock period value to maximum odr period (8kHz).
>
>Fixes: 0ecc363ccea7 ("iio: make invensense timestamp module generic")
>Cc: stable@vger.kernel.org
>Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
>---
> drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c | 4 ++--
> drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c  | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
>index 532d5fdffaf8..7df920ef3cf0 100644
>--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
>+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
>@@ -1170,10 +1170,10 @@ struct iio_dev *inv_icm42600_accel_init(struct inv_icm42600_state *st)
>        accel_st->filter = INV_ICM42600_FILTER_AVG_16X;
>
>        /*
>-        * clock period is 32kHz (31250ns)
>+        * clock period is 8kHz (125000ns)
>         * jitter is +/- 2% (20 per mille)
>         */
>-       ts_chip.clock_period = 31250;
>+       ts_chip.clock_period = 125000;
>        ts_chip.jitter = 20;
>        ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
>        inv_sensors_timestamp_init(&accel_st->ts, &ts_chip);
>diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
>index 11339ddf1da3..a18dcac93929 100644
>--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
>+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
>@@ -755,10 +755,10 @@ struct iio_dev *inv_icm42600_gyro_init(struct inv_icm42600_state *st)
>        }
>
>        /*
>-        * clock period is 32kHz (31250ns)
>+        * clock period is 8kHz (125000ns)
>         * jitter is +/- 2% (20 per mille)
>         */
>-       ts_chip.clock_period = 31250;
>+       ts_chip.clock_period = 125000;
>        ts_chip.jitter = 20;
>        ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
>        inv_sensors_timestamp_init(&gyro_st->ts, &ts_chip);
>
>---
>base-commit: cc746297b23e89bd5df9f91f3a0ca209e8991763
>change-id: 20260623-inv-icm42600-fix-timestamp-clock-period-931338a848c3
>
>Best regards,
>--
>Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
>
>

Hello Jonathan,

any update about this patch?

Thanks,
JB

Re: [PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value

[Jonathan Cameron]

On Tue, 23 Jun 2026 16:22:15 +0200
Jean-Baptiste Maneyrol via B4 Relay <devnull+jean-baptiste.maneyrol.tdk.com@kernel.org> wrote:

> From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
> 
Sorry for delay - I'm finally getting back on top of my emails (for IIO anyway!)

> Clock period value is used for computing periods of sampling. There is
> no need for it to be higher than the maximum odr, otherwise we are
> losing precision in the computation for nothing.

Silly question - what are the user visible results of that precision loss?

Less accurate time stamp estimates, or something else?

Jonathan


> 
> Switch clock period value to maximum odr period (8kHz).
> 
> Fixes: 0ecc363ccea7 ("iio: make invensense timestamp module generic")
> Cc: stable@vger.kernel.org
> Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>


> ---
>  drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c | 4 ++--
>  drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c  | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> index 532d5fdffaf8..7df920ef3cf0 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> @@ -1170,10 +1170,10 @@ struct iio_dev *inv_icm42600_accel_init(struct inv_icm42600_state *st)
>  	accel_st->filter = INV_ICM42600_FILTER_AVG_16X;
>  
>  	/*
> -	 * clock period is 32kHz (31250ns)
> +	 * clock period is 8kHz (125000ns)
>  	 * jitter is +/- 2% (20 per mille)
>  	 */
> -	ts_chip.clock_period = 31250;
> +	ts_chip.clock_period = 125000;
>  	ts_chip.jitter = 20;
>  	ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
>  	inv_sensors_timestamp_init(&accel_st->ts, &ts_chip);
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> index 11339ddf1da3..a18dcac93929 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> @@ -755,10 +755,10 @@ struct iio_dev *inv_icm42600_gyro_init(struct inv_icm42600_state *st)
>  	}
>  
>  	/*
> -	 * clock period is 32kHz (31250ns)
> +	 * clock period is 8kHz (125000ns)
>  	 * jitter is +/- 2% (20 per mille)
>  	 */
> -	ts_chip.clock_period = 31250;
> +	ts_chip.clock_period = 125000;
>  	ts_chip.jitter = 20;
>  	ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
>  	inv_sensors_timestamp_init(&gyro_st->ts, &ts_chip);
> 
> ---
> base-commit: cc746297b23e89bd5df9f91f3a0ca209e8991763
> change-id: 20260623-inv-icm42600-fix-timestamp-clock-period-931338a848c3
> 
> Best regards,
> --  
> Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
> 
> 

Re: [PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value

[Jean-Baptiste Maneyrol]

>From: Jonathan Cameron <jic23@kernel.org>
>Sent: Friday, July 3, 2026 21:02
>To: Jean-Baptiste Maneyrol via B4 Relay
>Cc: Jean-Baptiste Maneyrol; David Lechner; Nuno Sá; Andy Shevchenko; linux-iio@vger.kernel.org; linux-kernel@vger.kernel.org; stable@vger.kernel.org
>Subject: Re: [PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value
>
>On Tue, 23 Jun 2026 16: 22: 15 +0200 Jean-Baptiste Maneyrol via B4 Relay <devnull+jean-baptiste. maneyrol. tdk. com@ kernel. org> wrote: > From: Jean-Baptiste Maneyrol <jean-baptiste. maneyrol@ tdk. com> > Sorry for delay - I'm finally
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>On Tue, 23 Jun 2026 16:22:15 +0200
>Jean-Baptiste Maneyrol via B4 Relay <devnull+jean-baptiste.maneyrol.tdk.com@kernel.org> wrote:
>
>> From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
>>
>Sorry for delay - I'm finally getting back on top of my emails (for IIO anyway!)
>
>> Clock period value is used for computing periods of sampling. There is
>> no need for it to be higher than the maximum odr, otherwise we are
>> losing precision in the computation for nothing.
>
>Silly question - what are the user visible results of that precision loss?
>
>Less accurate time stamp estimates, or something else?
>
>Jonathan
>
Hello Jonathan,

that's not a silly question, it will effectively lead to less accurate timestamps.

We are measuring the delta time between 2 interrupts, and for abstracting the ODR
we divide this measurement to go to the configured clock period. Then we compute timestamps by multiplying back this measured clock period. If we divide
too much, we are losing precision. Since maximum ODR is 8kHz, there is no
need to go further than this value. Internal chip clock is 32kHz, but maximum
ODR is 8kHz.

Thanks,
JB

>
>>
>> Switch clock period value to maximum odr period (8kHz).
>>
>> Fixes: 0ecc363ccea7 ("iio: make invensense timestamp module generic")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
>
>
>> ---
>>  drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c | 4 ++--
>>  drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c  | 4 ++--
>>  2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
>> index 532d5fdffaf8..7df920ef3cf0 100644
>> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
>> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
>> @@ -1170,10 +1170,10 @@ struct iio_dev *inv_icm42600_accel_init(struct inv_icm42600_state *st)
>>       accel_st->filter = INV_ICM42600_FILTER_AVG_16X;
>>
>>       /*
>> -      * clock period is 32kHz (31250ns)
>> +      * clock period is 8kHz (125000ns)
>>        * jitter is +/- 2% (20 per mille)
>>        */
>> -     ts_chip.clock_period = 31250;
>> +     ts_chip.clock_period = 125000;
>>       ts_chip.jitter = 20;
>>       ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
>>       inv_sensors_timestamp_init(&accel_st->ts, &ts_chip);
>> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
>> index 11339ddf1da3..a18dcac93929 100644
>> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
>> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
>> @@ -755,10 +755,10 @@ struct iio_dev *inv_icm42600_gyro_init(struct inv_icm42600_state *st)
>>       }
>>
>>       /*
>> -      * clock period is 32kHz (31250ns)
>> +      * clock period is 8kHz (125000ns)
>>        * jitter is +/- 2% (20 per mille)
>>        */
>> -     ts_chip.clock_period = 31250;
>> +     ts_chip.clock_period = 125000;
>>       ts_chip.jitter = 20;
>>       ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
>>       inv_sensors_timestamp_init(&gyro_st->ts, &ts_chip);
>>
>> ---
>> base-commit: cc746297b23e89bd5df9f91f3a0ca209e8991763
>> change-id: 20260623-inv-icm42600-fix-timestamp-clock-period-931338a848c3
>>
>> Best regards,
>> --
>> Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
>>
>>

Re: [PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value

[Jonathan Cameron]

On Mon, 6 Jul 2026 08:00:43 +0000
Jean-Baptiste Maneyrol <Jean-Baptiste.Maneyrol@tdk.com> wrote:

> >From: Jonathan Cameron <jic23@kernel.org>
> >Sent: Friday, July 3, 2026 21:02
> >To: Jean-Baptiste Maneyrol via B4 Relay
> >Cc: Jean-Baptiste Maneyrol; David Lechner; Nuno Sá; Andy Shevchenko; linux-iio@vger.kernel.org; linux-kernel@vger.kernel.org; stable@vger.kernel.org
> >Subject: Re: [PATCH] iio: imu: inv_icm42600: fix timestamp clock period by using lower value
> >
> >On Tue, 23 Jun 2026 16: 22: 15 +0200 Jean-Baptiste Maneyrol via B4 Relay <devnull+jean-baptiste. maneyrol. tdk. com@ kernel. org> wrote: > From: Jean-Baptiste Maneyrol <jean-baptiste. maneyrol@ tdk. com> > Sorry for delay - I'm finally
> >ZjQcmQRYFpfptBannerStart
> >This Message Is From an External Sender
> >This message came from outside your organization.
> >
> >ZjQcmQRYFpfptBannerEnd
> >
> >On Tue, 23 Jun 2026 16:22:15 +0200
> >Jean-Baptiste Maneyrol via B4 Relay <devnull+jean-baptiste.maneyrol.tdk.com@kernel.org> wrote:
> >  
> >> From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
> >>  
> >Sorry for delay - I'm finally getting back on top of my emails (for IIO anyway!)
> >  
> >> Clock period value is used for computing periods of sampling. There is
> >> no need for it to be higher than the maximum odr, otherwise we are
> >> losing precision in the computation for nothing.  
> >
> >Silly question - what are the user visible results of that precision loss?
> >
> >Less accurate time stamp estimates, or something else?
> >
> >Jonathan
> >  
> Hello Jonathan,
> 
> that's not a silly question, it will effectively lead to less accurate timestamps.
> 
> We are measuring the delta time between 2 interrupts, and for abstracting the ODR
> we divide this measurement to go to the configured clock period. Then we compute timestamps by multiplying back this measured clock period. If we divide
> too much, we are losing precision. Since maximum ODR is 8kHz, there is no
> need to go further than this value. Internal chip clock is 32kHz, but maximum
> ODR is 8kHz.
> 
Seems I applied this and forgot to say so.  Anyhow, now upstream.

Jonathan

> Thanks,
> JB
> 
> >  
> >>
> >> Switch clock period value to maximum odr period (8kHz).
> >>
> >> Fixes: 0ecc363ccea7 ("iio: make invensense timestamp module generic")
> >> Cc: stable@vger.kernel.org
> >> Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>  
> >
> >  
> >> ---
> >>  drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c | 4 ++--
> >>  drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c  | 4 ++--
> >>  2 files changed, 4 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> >> index 532d5fdffaf8..7df920ef3cf0 100644
> >> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> >> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> >> @@ -1170,10 +1170,10 @@ struct iio_dev *inv_icm42600_accel_init(struct inv_icm42600_state *st)
> >>       accel_st->filter = INV_ICM42600_FILTER_AVG_16X;
> >>
> >>       /*
> >> -      * clock period is 32kHz (31250ns)
> >> +      * clock period is 8kHz (125000ns)
> >>        * jitter is +/- 2% (20 per mille)
> >>        */
> >> -     ts_chip.clock_period = 31250;
> >> +     ts_chip.clock_period = 125000;
> >>       ts_chip.jitter = 20;
> >>       ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
> >>       inv_sensors_timestamp_init(&accel_st->ts, &ts_chip);
> >> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> >> index 11339ddf1da3..a18dcac93929 100644
> >> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> >> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> >> @@ -755,10 +755,10 @@ struct iio_dev *inv_icm42600_gyro_init(struct inv_icm42600_state *st)
> >>       }
> >>
> >>       /*
> >> -      * clock period is 32kHz (31250ns)
> >> +      * clock period is 8kHz (125000ns)
> >>        * jitter is +/- 2% (20 per mille)
> >>        */
> >> -     ts_chip.clock_period = 31250;
> >> +     ts_chip.clock_period = 125000;
> >>       ts_chip.jitter = 20;
> >>       ts_chip.init_period = inv_icm42600_odr_to_period(st->conf.accel.odr);
> >>       inv_sensors_timestamp_init(&gyro_st->ts, &ts_chip);
> >>
> >> ---
> >> base-commit: cc746297b23e89bd5df9f91f3a0ca209e8991763
> >> change-id: 20260623-inv-icm42600-fix-timestamp-clock-period-931338a848c3
> >>
> >> Best regards,
> >> --
> >> Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
> >>
> >