Tahiti and Hawaii (without amdgpu support) skips vblanks on wayland (weston and others) on some displays.
Submitted by John Galt
Assigned to Default DRI bug account
Description
When running weston on this hardware with Shimian QHD270 displays, vblanks are skipped resulting in stuttering video playback on any framerate other than 60fps (with multiple players and vo including opengl and wayland (shm)).
System:
Mesa: git
linux: 4.4, 4.5, 4.6 from a drm-next-wip branch
wayland: git
weston: git
A few notes:
- This doesn't occur when using amdgpu (for instance building with hawaii amdgpu support.
- This bug goes back as far as a year, and another user verified they had this issue on a radeonsi card with a specific monitor.
- When utilizing amdgpu, the EDID is correctly read from these monitors. Without, the EDID read fails. I've written the EDID to a file in /lib/firmware/ and successfully loaded with no change however.
- Outside of video playback, there are no vblank skips. It was explained that each application affects the entire compositor.
- No change on video size. The issue is apparent (with no discernible change) on non-60fps 360p youtube videos on up to high bitrate x265 4K tv shows.
- By increasing repaint-window, I'm able to get consistent playback and no vblank skips. However I do run into other issues with it, showing it's clearly not a real solution for wayland support on radeon.
- During video playback, weston-presentation-shm shows the missing vblanks just as a timeline does (so including weston-presentation-shm log for readability instead).
weston-presentation-shm log with video playback at beginning: https://bpaste.net/show/f8c9b910ddc1. When vblanks are no longer skipped, the video playback has stopped.