[PATCH 4/7] drm/vc4: Use drm_atomic_helper_wait_for_flip_done()

[Eric Anholt]

Boris Brezillon <boris.brezillon at free-electrons.com> 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?

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?
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