From a78e7a51d2fa9d2f482b462be4299784c884d988 Mon Sep 17 00:00:00 2001 From: Veera Sundaram Sankaran Date: Fri, 15 Jan 2021 16:31:47 -0800 Subject: drm/drm_vblank: set the dma-fence timestamp during send_vblank_event 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 Changes in v4: - remove WARN_ON from drm_send_event_timestamp_locked Signed-off-by: Veera Sundaram Sankaran Reviewed-by: John Stultz Signed-off-by: Sumit Semwal [sumits: minor parenthesis alignment correction] Link: https://patchwork.freedesktop.org/patch/msgid/1610757107-11892-2-git-send-email-veeras@codeaurora.org --- drivers/gpu/drm/drm_vblank.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/drm_vblank.c') diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 30912d8f82a5..893165eeddf3 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1006,7 +1006,14 @@ static void send_vblank_event(struct drm_device *dev, break; } trace_drm_vblank_event_delivered(e->base.file_priv, e->pipe, seq); - drm_send_event_locked(dev, &e->base); + /* + * Use the same timestamp for any associated fence signal to avoid + * mismatch in timestamps for vsync & fence events triggered by the + * same HW event. Frameworks like SurfaceFlinger in Android expects the + * retire-fence timestamp to match exactly with HW vsync as it uses it + * for its software vsync modeling. + */ + drm_send_event_timestamp_locked(dev, &e->base, now); } /** -- cgit v1.2.3