github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-28 10:09:10 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

media: uvcvideo: Relax the constrains for interpolating the hw clock

Browse Source 
In the initial version we set the min value to 250msec. Looks like
100msec can also provide a good value.

Now that we are at it, add a macro to make it cleaner.

Fixes: 6243c83be6 ("media: uvcvideo: Allow hw clock updates with buffers not full")
Cc: stable@vger.kernel.org
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Tested-by: Yunke Cao <yunkec@google.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Link: https://patch.msgid.link/20260513-uvc-hwtimestamp-v3-3-7a64838b0b02@chromium.org
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
This commit is contained in:
Ricardo Ribalda 2026-05-13 11:49:22 +00:00 committed by Hans Verkuil
parent ede7de6e6b
commit 1719d78f83
1 changed files with 12 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/media/usb/uvc/uvc_video.c
View File

@ -494,6 +494,13 @@ static int uvc_commit_video(struct uvc_streaming *stream,
* Clocks and timestamps
*/
/*
* The accuracy of the hardware timestamping depends on having enough data to
* interpolate between the different clock domains. This value is sof cycles,
* this is, milliseconds.
*/
#define UVC_MIN_HW_TIMESTAMP_DIFF 100
static inline ktime_t uvc_video_get_time(void)
{
if (uvc_clock_param == CLOCK_MONOTONIC)
@ -843,13 +850,13 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
* buffer, but RAM is expensive these days, specially the infinitely
* big.
*
* The value of 1/4th of a second was determined by running Android's
* CTS on different devices.
* The value of UVC_MIN_HW_TIMESTAMP_DIFF was determined by running
* Android's CTS on different devices.
*
* dev_sof runs at 1KHz, and we have a fixed point precision of
* 16 bits.
* y1 and y2 are dev_sof with a fixed point precision of 16 bits.
*/
if (clock->size != clock->count && (y2 - y1) < ((1000 / 4) << 16))
if (clock->size != clock->count &&
(y2 - y1) < (UVC_MIN_HW_TIMESTAMP_DIFF << 16))
goto done;
y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2