media: uvcvideo: Fix dev_sof filtering in hw timestamp

To avoid filling the clock circular buffer with duplicated data we only
add it if the new value sof is different than the last added sof.

The issue is that we compare the unprocess sof with the processed sof.
If there is a sof_offset, or UVC_QUIRK_INVALID_DEVICE_SOF is enabled,
the comparison will not work as expected.

This patch moves the comparison to the right place.

Fixes: 141270bd95d4 ("media: uvcvideo: Refactor clock circular buffer")
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-v3-1-7a64838b0b02@chromium.org
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 0e691b8727017a15a8695c0a63e4ebee65d2413d..efd746dd5db01c61f46ced74a5be34deb7cc7fd1 100644 (file)
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -583,16 +583,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
        if (!has_scr)
                return;
 
-       /*
-        * To limit the amount of data, drop SCRs with an SOF identical to the
-        * previous one. This filtering is also needed to support UVC 1.5, where
-        * all the data packets of the same frame contains the same SOF. In that
-        * case only the first one will match the host_sof.
-        */
        sample.dev_sof = get_unaligned_le16(&data[header_size - 2]);
-       if (sample.dev_sof == stream->clock.last_sof)
-               return;
-
        sample.dev_stc = get_unaligned_le32(&data[header_size - 6]);
 
        /*
@@ -664,6 +655,16 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
        }
 
        sample.dev_sof = (sample.dev_sof + stream->clock.sof_offset) & 2047;
+
+       /*
+        * To limit the amount of data, drop SCRs with an SOF identical to the
+        * previous one. This filtering is also needed to support UVC 1.5, where
+        * all the data packets of the same frame contains the same SOF. In that
+        * case only the first one will match the host_sof.
+        */
+       if (sample.dev_sof == stream->clock.last_sof)
+               return;
+
        uvc_video_clock_add_sample(&stream->clock, &sample);
        stream->clock.last_sof = sample.dev_sof;
 }