ACK: [SRU][J][PATCH 0/1] Black screen when booting 5.15.0-160 (on AMD Lucienne / Cezanne / Navi / Renoir / Rembrandt)

[Tim Whisonant]

On Mon, Dec 08, 2025 at 05:38:16PM +0100, Manuel Diewald wrote:
> BugLink: https://bugs.launchpad.net/bugs/2128729
> 
> SRU Justification:
> 
> [Impact]
> 
> The Ubuntu backport of e6a7df96facdc ("drm/amd/display: Fix MST Null Ptr
> for RV") to fix CVE-2024-26700 does not consider that
> compute_mst_dsc_configs_for_state() returns a boolean to
> indicate success or failure in 5.15, while it returns an integer
> in later kernel versions with 0 indicating success. This means
> we need to flip the error condition when checking whether the
> call succeeded when backporting this to 5.15 and older.
>     
> Currently, the error path is taken even though the call to
> compute_mst_dsc_configs_for_state() succeeds which causes some systems
> to have no video output or a black screen while the system is running.
> 
> This is causing loss of video output to screens on affected amdgpu
> hardware.
> 
> [Fix]
> 
> Check the return value of compute_mst_dsc_configs_for_state() in
> amdgpu_dm_atomic_check() correctly.
> 
> [Test Plan]
> 
> Without the fix, there will be no video output to the screen and the
> following messages can be found in the kernel log if the kernel is
> booted with drm.debug=0x2:
> 
> kernel: [drm:amdgpu_dm_atomic_check [amdgpu]] compute_mst_dsc_configs_for_state() failed
> kernel: [drm:amdgpu_dm_atomic_check [amdgpu]] Atomic check failed with err: -22
> 
> With the fix applied, video output should return to normal and the
> kernel warnings will disappear from the log.
> 
> [Where problems could occur]
> 
> Problems would be observed in odd behavior of the amdgpu driver,
> particularly for hardware with DSC support.
> 
> Manuel Diewald (1):
>   UBUNTU: SAUCE: drm/amd/display: Fix incorrect code path taken in
>     amdgpu_dm_atomic_check()
> 
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> -- 
> 2.34.1
> 
> 

Acked-by: Tim Whisonant <tim.whisonant at canonical.com>