media: uvcvideo: Do not add clock samples with small sof delta

media: uvcvideo: Do not add clock samples with small sof delta

Some UVC 1.1 cameras running in fast isochronous mode tend to spam the
USB host with a lot of empty packets. These packets contain clock
information and are added to the clock buffer but do not add any
accuracy to the calculation. In fact, it is quite the opposite, in our
calculations, only the first and the last timestamp is used, and we only
have 32 slots.

Ignore the samples that will produce less than MIN_HW_TIMESTAMP_DIFF
data.

Fixes: 141270bd95d4 ("media: uvcvideo: Refactor clock circular buffer")
Cc: stable@vger.kernel.org
Tested-by: Yunke Cao <yunkec@google.com>
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Link: https://patch.msgid.link/20260513-uvc-hwtimestamp-v3-4-7a64838b0b02@chromium.org
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>