[PATCH 2/4] media: uvcvideo: Use hw timestaming if the clock buffer is full

[Ricardo Ribalda <ribalda@chromium.org>]

In some situations, even with a full clock buffer, it does not contain
250msec of data. This results in the driver jumping back from software
to hardware timestapsing creating a nasty artifact in the video.

If the clock buffer is full, use it to calculate the timestamp instead
of defaulting to software stamps, the reduced accuracy is less visible
than jumping from one timestamping mechanism to the other.

Fixes: 6243c83be6ee8 ("media: uvcvideo: Allow hw clock updates with buffers not full")
Cc: stable@vger.kernel.org
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 6786ca38fe5e..c7ebedb3450f 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -842,7 +842,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
 	 * dev_sof runs at 1KHz, and we have a fixed point precision of
 	 * 16 bits.
 	 */
-	if ((y2 - y1) < ((1000 / 4) << 16))
+	if (clock->size != clock->count && (y2 - y1) < ((1000 / 4) << 16))
 		goto done;
 
 	y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2

-- 
2.53.0.959.g497ff81fa9-goog