[SRU][R][PATCH 0/1] amdgpu: Fix garbled display when switching workspaces

[Aaron Ma]

BugLink: https://bugs.launchpad.net/bugs/2166730

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:
48ab86360af1 ("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.

Leo Li (1):
  drm/amd/display: check GRPH_FLIP status before sending event

 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 191 ++++++++++++++----
 drivers/gpu/drm/amd/display/dc/core/dc.c      |  44 ++++
 drivers/gpu/drm/amd/display/dc/dc.h           |   1 +
 3 files changed, 196 insertions(+), 40 deletions(-)

-- 
2.53.0