Re: [PATCH v2 0/2] drm/amd/display: Keep FreeSync flip timing across plane resets

[Harry Wentland <harry.wentland@amd.com>]

On 10/28/26 18:54, Davey Hughes via B4 Relay wrote:
> On a 48-165 Hz FreeSync panel, fullscreen clients under KWin with HDR
> enabled and color accuracy set to "Prefer efficiency" run at about 51
> fps instead of 60, with flips locked to the 13.45 ms BTR mid-point
> grid. That grid drifts upward at the rate expected if FreeSync takes
> the 32-bit microsecond timestamp itself as the last render time (3.46
> us/s measured, 3.45 predicted).
>
> KWin replaces the CRTC GAMMA_LUT blob on every commit in that mode, so
> every flip resets the plane and the new DC plane starts with zeroed
> flip timing. Patch 1 carries the timing over from the old DC plane, as
> DM already does for flip_addr
> (amdgpu_dm_plane_drm_plane_duplicate_state()) and for the BTR state
> itself (dm_irq_params.vrr_params). Patch 2 adds KUnit tests, kept
> separate so patch 1 backports to stable trees without the KUnit
> infrastructure.
>
> Tested with KUnit (UML, all AMD display suites pass; the new timing
> tests fail without the fix) and on 7.2.11 with a Navi 31, an AW3423DWF
> over DP, KWin 6.8.1 and Mesa 26.2.5: 60 fps content now flips at a
> steady 16.65 ms instead of on the 13.45 ms grid, 30 fps content still
> gets BTR (30 fps, no 13.45 ms grid), and debugfs shows
> color_mgmt_changed=1 on the CRTC in every sampled commit. Not tested:
> DCE, overlay planes, other compositors.
>
> I am not sure of the current AI disclosure policy, but I will freely
> mention that I used Claude Opus 5.5 to help debug and write this patch +
> tests. I have tried to do my best to match existing style/procedures.
>

Series is
Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> ---
> Changes in v2:
> - Copy the flip timing in amdgpu_dm_commit_planes() instead of in
>   atomic check, so it can't race with the previous commit still writing
>   it (reported by Sashiko AI review)
> - Skip the copy when the plane keeps its DC plane
> - Add dm_plane_inherit_flip_time() in patch 1; patch 2 only exposes it
>   to KUnit
> - Check the whole flip timing struct in the KUnit tests
> - Link to v1: https://patch.msgid.link/20261027-freesync-plane-reset-time-v1-0-bb43b501faf4@gmail.com
>
> ---
> Davey Hughes (2):
>       drm/amd/display: Keep FreeSync flip timing across plane resets
>       drm/amd/display: Test FreeSync flip timing across plane resets
>
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c  |  23 +++
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h  |   3 +
>  .../amd/display/amdgpu_dm/tests/amdgpu_dm_test.c   | 188 +++++++++++++++++++++
>  3 files changed, 214 insertions(+)
> ---
> base-commit: 77f548b127c6de34ce271fa09ba270cb1ef9f2da
> change-id: 20261027-freesync-plane-reset-time-5db657eebfde
>
> Best regards,
> --  
> Davey Hughes <davidralphhughes@gmail.com>