On Wed, Jan 13, 2021 at 11:52 AM Veera Sundaram Sankaran veeras@codeaurora.org wrote:
The explicit out-fences in crtc are signaled as part of vblank event, indicating all framebuffers present on the Atomic Commit request are scanned out on the screen. Though the fence signal and the vblank event notification happens at the same time, triggered by the same hardware vsync event, the timestamp set in both are different. With drivers supporting precise vblank timestamp the difference between the two timestamps would be even higher. This might have an impact on use-mode frameworks using these fence timestamps for purposes other than simple buffer usage. For instance, the Android framework [1] uses the retire-fences as an alternative to vblank when frame-updates are in progress. Set the fence timestamp during send vblank event using a new drm_send_event_timestamp_locked variant to avoid discrepancies.
[1] https://android.googlesource.com/platform/frameworks/native/+/master/ services/surfaceflinger/Scheduler/Scheduler.cpp#397
Changes in v2:
- Use drm_send_event_timestamp_locked to update fence timestamp
- add more information to commit text
Changes in v3:
- use same backend helper function for variants of drm_send_event to
avoid code duplications
Signed-off-by: Veera Sundaram Sankaran veeras@codeaurora.org
Looks good. I appreciate you addressing my earlier comments and sending this out again!
Reviewed-by: John Stultz john.stultz@linaro.org
thanks -john