On Thu, Nov 12, 2020 at 10:27:23AM -0800, Veera Sundaram Sankaran 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 uses the retire-fences > as an alternative to vblank when frame-updates are in progress Set the > fence timestamp during send vblank event to avoid discrepancies.
I think a reference to the exact source code in android that does this would be really useful. Something in drm_hwcomposer or whatever is doing this. Aside from documenting why we want to do this I think this all looks reasonable. -Daniel > > Signed-off-by: Veera Sundaram Sankaran <vee...@codeaurora.org> > --- > drivers/gpu/drm/drm_vblank.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > index b18e1ef..b38e50c 100644 > --- a/drivers/gpu/drm/drm_vblank.c > +++ b/drivers/gpu/drm/drm_vblank.c > @@ -24,6 +24,7 @@ > * OTHER DEALINGS IN THE SOFTWARE. > */ > > +#include <linux/dma-fence.h> > #include <linux/export.h> > #include <linux/kthread.h> > #include <linux/moduleparam.h> > @@ -999,6 +1000,14 @@ static void send_vblank_event(struct drm_device *dev, > e->event.seq.time_ns = ktime_to_ns(now); > break; > } > + > + /* > + * update fence timestamp with the same vblank timestamp as both > + * are signaled by the same event > + */ > + if (e->base.fence) > + e->base.fence->timestamp = now; > + > trace_drm_vblank_event_delivered(e->base.file_priv, e->pipe, seq); > drm_send_event_locked(dev, &e->base); > } > -- > 2.7.4 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
