On Wed, Nov 06, 2024 at 01:34:37PM +0100, Stanislaw Gruszka wrote:
> On some Lenovo platforms, the patch workarounds problems with ov2740
> sensor initialization, which manifest themself like below:
>
> [ 4.540476] ov2740 i2c-INT3474:01: error -EIO: failed to find sensor
> [ 4.542066] ov2740 i2c-INT3474:01: probe with driver ov2740 failed with error -5
>
> or
>
> [ 7.742633] ov2740 i2c-INT3474:01: chip id mismatch: 2740 != 0
> [ 7.742638] ov2740 i2c-INT3474:01: error -ENXIO: failed to find sensor
>
> and also by random failures of video stream start.
>
> Issue can be reproduced by this script:
>
> n=0
> k=0
> while [ $n -lt 50 ] ; do
> sudo modprobe -r ov2740
> sleep `expr $RANDOM % 5`
> sudo modprobe ov2740
> if media-ctl -p | grep -q ov2740 ; then
> let k++
> fi
> let n++
> done
> echo Success rate $k/$n
>
> Without the patch, success rate is approximately 15 or 50 tries.
> With the patch it does not fail.
>
> This problem is some hardware or firmware malfunction, that can not be
> easy debug and fix. While setting small autosuspend delay is not perfect
> workaround as user can configure it to any value, it will prevent
> the failures by default.
>
> Additionally setting small autosuspend delay should have positive effect
> on power consumption as for most ljca workloads device is used for just
> a few milliseconds flowed by long periods of at least 100ms of inactivity
> (usually more).
>
> Fixes: acd6199f195d ("usb: Add support for Intel LJCA device")
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> Tested-by: Hans de Goede <hdegoede@xxxxxxxxxx> # ThinkPad X1 Yoga Gen 8, ov2740
> Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@xxxxxxxxxxxxxxx>
Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
--
Sakari Ailus
