On 8/24/26 22:38, Viktor Jägersküpper wrote:
> [ Adding Timur ]
>
> On 8/13/26 16:30, Melissa Wen wrote:
>> DCE can support PREMULTI and COVERAGE blend mode depending on its
>> generation, however current driver implementation either doesn't expose
>> more than primary and cursor plane, or doesn't program registers for any
>> blend mode other than PIXEL_NONE. To fix the missing-blend-mode-prop
>> warning according to current DCE plane caps, create blend mode property
>> with PIXEL_NONE only for primary planes, instead of the DRM default
>> PREMULTI.
>>
>> Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with
>> alpha exposed")
>> Reviewed-by: Leandro Ribeiro <[email protected]>
>> Signed-off-by: Melissa Wen <[email protected]>
>>
>> ---
>> v3:
>> - fix indentation (Alex H)
>> ---
>> .../amd/display/amdgpu_dm/amdgpu_dm_plane.c | 18 +++++++++++-------
>> 1 file changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
>> index ab9bbe8ca333..3b5b6943b67d 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
>> @@ -1923,14 +1923,18 @@ int amdgpu_dm_plane_init(struct
>> amdgpu_display_manager *dm,
>> if (res)
>> return res;
>>
>> - /* TODO: Check which blend modes are supported in DCE-generation
>> - * planes, i.e. DC_PLANE_TYPE_DCE_RGB/UNDERLAY and expose blend mode
>> - * property accordingly.
>> + /* Blend mode support varies on DCE generations according to HW caps
>> + * and number of planes per CRTC. However, as current driver
>> + * implementation only creates one primary and one cursor plane per
>> + * CRTC for DCE (overlay is only created if
>> + * DC_PLANE_TYPE_DCN_UNIVERSAL), the primary plane blend mode ends up
>> + * being always PIXEL_NONE across DCE versions.
>> */
>> - if ((plane->type == DRM_PLANE_TYPE_OVERLAY ||
>> - plane->type == DRM_PLANE_TYPE_PRIMARY) &&
>> - plane_cap && plane_cap->per_pixel_alpha &&
>> - plane_cap->type == DC_PLANE_TYPE_DCN_UNIVERSAL) {
>> + if (plane_cap && plane_cap->type != DC_PLANE_TYPE_DCN_UNIVERSAL) {
>> + drm_plane_create_blend_mode_property(plane,
>> BIT(DRM_MODE_BLEND_PIXEL_NONE));
>> + } else if ((plane->type == DRM_PLANE_TYPE_OVERLAY ||
>> + plane->type == DRM_PLANE_TYPE_PRIMARY) &&
>> + plane_cap && plane_cap->per_pixel_alpha) {
>> unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
>> BIT(DRM_MODE_BLEND_PREMULTI) |
>> BIT(DRM_MODE_BLEND_COVERAGE);
>
> With this patch applied to the mainline kernel, my display freezes when
> Kwin is started (either by SDDM or by launching a KDE Plasma session).
> GDM and Gnome work fine. The journal doesn't have much information, it's
> mainly this:
>
> kwin_wayland[8402]: Applying output configuration failed!
>
> and after that several KDE processes with:
>
> <kde_process>[xxxx]: There are no outputs - creating placeholder screen
>
> Any idea how I can debug this further? Maybe ask the KDE developers?
>
> With only the first two patches of this series applied, Kwin works as
> before, but I get the warnings of course.
I completely forgot that I'm observing this with AMD Pitcairn running
KDE 6.7.4 on Arch Linux. The kernel is built from source (mainline as of
today) with this patch series applied on top.
Viktor
