On Tue, 06 Jun 2017 13:24:33 -0700 Eric Anholt <eric@xxxxxxxxxx> wrote: > Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> writes: > > > Replace the drm_atomic_helper_wait_for_vblanks() with a call to > > drm_atomic_helper_wait_for_flip_done(). This allows better detection of > > page flip done events which what we are really waiting for in > > vc4_atomic_complete_commit(). > > > > With this approach, we also addresse the 'missed single vblank event' > > problem that can arise when the CRTC is configured in oneshot mode > > (only a single frame is generated and the CRTC is immediately paused > > after this frame). Note that this oneshot mode will be used for the > > writeback connector feature. > > Should we just use drm_atomic_helper_commit_tail() and make this change > in the core helper, instead? Hm, not sure changing the default behavior is such a good idea. I don't want to break other drivers. > > Actually, I'm confused. drm_atomic_helper_commit_cleanup_done() seems > to be waiting for the flip_done on the crtc, already. What's the > difference? Actually, drm_atomic_helper_wait_for_flip_done() is called just before drm_atomic_helper_cleanup_planes() which in turn is called before drm_atomic_helper_commit_cleanup_done(). My understanding was that it was unsafe to call plane->cleanup_fb() on FBs that are still in use, and the only thing guaranteeing that FBs are not used anymore is the flip_done event. Maybe I'm wrong, and FB refcounting is enough to make sure resources are preserved until page flip is actually done. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
