Is drmWaitVBlank() or drmModePageFlip necessary after drmModeSetPlane()

[Randy Li]

Hello all,
   Recently, I meet a performance problem with drmModeSetPlane(), it 
works quite slow with drm_atomic_commit(), I have to force it use 
drm_atomic_async_commit() for drmModeSetPlane() which modifies the drm 
base system. I want to optimize the performance in standard way, so I 
think I could move those sync job to one of drmWaitVBlank() or 
drmModePageFlip.
   But I found most of atomic_commit() would have a sync internal, 
waiting vbank. So those functions like drmWaitVBlank() or 
drmModePageFlip are not necessary after drmModeSetPlane()?
-- 
Randy Li
The third produce department