Public bug reported:
SRU Justification:
[ Impact ]
On AMD systems with DCN graphics, garbled display artifacts and horizontal
flickering occur when switching workspaces or playing video.
This is caused by a race condition where a page flip completion event is
delivered to userspace before the hardware has latched the flip.
Userspace then renders to the active display buffer, causing visual
corruption. PSR and Replay features widen this window.
[ Fix ]
Backport upstream commit 48ab86360af117123eb1b15e38f068acf3826400
("drm/amd/display: check GRPH_FLIP status before sending event"):
- Arm flip completion only after hardware programming completes.
- Query hardware flip-pending status directly via dc_get_flip_pending_on_otg().
- Only deliver completion in the VUPDATE_NO_LOCK handler once hardware confirms
the flip is complete.
- Optimistically send the event immediately if hardware latched during
programming.
[ Test Plan ]
1. On an AMD system with DCN graphics, switch repeatedly between workspaces and
play video.
2. Without the fix: Garbled display artifacts appear frequently.
3. With the fix: Workspaces switch smoothly with no screen corruption.
[ Where problems could occur ]
Changes affect the amdgpu display page flip completion path. If flip status is
misreported, page flip events could be delayed or missed, causing frame drops
or stutter.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2166730
Title:
[SRU] amdgpu: Fix garbled display when switching workspaces
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