Hi Ricardo,
Thank you for the patch.
On Fri, Dec 02, 2022 at 06:02:48PM +0100, Ricardo Ribalda wrote:
> In UVC 1.5, when working with FPS under 32, there is a chance that the
> circular buffer contains two dev_sof overflows,
An explanation of why this is the case would be good in the commit
message. Also, by overflow, are you talking about the SOF counter
rolling over ?
> but the clock interpolator
> is only capable of handle a single overflow.
>
> Remove all the samples from the circular buffer that are two overflows
> old.
I would rather support multiple roll-over in the clock interpolator.
Dropping older sampls will lead to less predictable behaviour and harder
to debug issues.
> Tested-by: HungNien Chen <hn.chen@xxxxxxxxxxxxx>
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
> drivers/media/usb/uvc/uvc_video.c | 15 +++++++++++++++
> drivers/media/usb/uvc/uvcvideo.h | 1 +
> 2 files changed, 16 insertions(+)
>
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index c81a8362d582..6b6bd521d6c2 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -471,6 +471,20 @@ static void uvc_video_clock_add_sample(struct uvc_clock *clock,
>
> spin_lock_irqsave(&clock->lock, flags);
>
> + /* Delete last overflows */
> + if (clock->head == clock->last_sof_overflow)
> + clock->last_sof_overflow = -1;
> +
> + /* Handle overflows */
> + if (clock->count > 0 && clock->last_sof > sample->dev_sof) {
> + /* Remove data from the last^2 overflows */
> + if (clock->last_sof_overflow != -1)
> + clock->count = (clock->head - clock->last_sof_overflow)
> + % clock->count;
> + clock->last_sof_overflow = clock->head;
> + }
> +
> + /* Add sample */
> memcpy(&clock->samples[clock->head], sample, sizeof(*sample));
> clock->last_sof = sample->dev_sof;
> clock->head = (clock->head + 1) % clock->size;
> @@ -594,6 +608,7 @@ static void uvc_video_clock_reset(struct uvc_clock *clock)
> clock->head = 0;
> clock->count = 0;
> clock->last_sof = -1;
> + clock->last_sof_overflow = -1;
> clock->sof_offset = -1;
> }
>
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index 14daa7111953..d8c520ce5a86 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -647,6 +647,7 @@ struct uvc_streaming {
> unsigned int head;
> unsigned int count;
> unsigned int size;
> + unsigned int last_sof_overflow;
>
> u16 last_sof;
> u16 sof_offset;
--
Regards,
Laurent Pinchart
