drm/vc4: Use wait_for_flip_done() instead of wait_for_vblanks()
drm_atomic_helper_wait_for_vblanks() assumes the CRTC will continuously generate VBLANK events and the vblank counter will keep increasing. While this work for a regular pipeline, it doesn't when you have the CRTC is feeding the transposer block, because this block works in oneshot mode, and, by the time we reach drm_atomic_helper_wait_for_vblanks() the only VBLANK event might have already been sent and the VBLANK counter will stay unchanged, thus triggering a timeout. Luckily, we can replace the drm_atomic_helper_wait_for_vblanks() call by drm_atomic_helper_wait_for_flip_done() because the only thing we want to check when calling drm_atomic_helper_wait_for_vblanks() from vc4_atomic_complete_commit() is that new FBs are in use and the old ones can be safely released. Signed-off-by: NBoris Brezillon <boris.brezillon@bootlin.com> Reviewed-by: NLiviu Dudau <liviu.dudau@arm.com> Reviewed-by: NEric Anholt <eric@anholt.net> Link: https://patchwork.freedesktop.org/patch/msgid/20180703075022.15138-5-boris.brezillon@bootlin.com
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