[PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Melissa Wen]

PREMULTI was the default DRM blend mode until 9813e158d13d
("drm/drm_blend: allow blend mode property without PREMULTI") introduced
the possibility of exposing the blend mode property without PREMULTI
being supported. However, __drm_atomic_helper_plane_state_init() still
resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
mode in this property. In the same series, 860e748bddcc ("drm: ensure
blend mode supported if pixel format with alpha exposed") starts warning
drivers that supports alpha formats in a given planes but doesn't
support blend mode property, which includes AMD primary and cursor
planes.

For AMD DCN families, overlay and primary planes support the three blend
modes, and therefore PREMULTI is still the default mode. So the warning
can be fixed by just creating blend mode properties for primary planes
too. PREMULTI is the default/unique mode for cursor planes in DCN and
DCE driver. However, looks like PIXEL_NONE is the unique blend mode
supported by DCE-generation driver. I don't have the hardware to check
it out, but looking at the code I understand that, even if the hardware
can do PREMULTI or COVERAGE, the way it programs registers doesn't make
these other blend modes actually available.

Bearing this in mind, this series is organized as follow:

- Patch 1 fixes the pixel_blend_mode reset when the blend mode property
  is advertised without PREMULTI support. It's needed for AMD
  DCE-generation (patch 3) and I think with this we can also remove a
  workaround in nouveau nv50_wndw_default_state() caused by the
  hardcoded PREMULTI default value [1].

- Patch 2 fixes the missing-blend-mode-property warning for DCN primary
  plane and for DCN+DCE cursor plane. The alpha property keeps only on
  overlay planes because looks like this is not supported by AMD primary
  planes and it doesn't affect the blend mode warning we are targetting.
  Enabling alpha properties to primary was also causing -EINVAL on IGT
  alpha tests because it started testing primary planes and disabling it
  (which is not allowed by the AMD display driver).

- Patch 3 fixes the warning for DCE primary plane, but I detached this
  solution from the previous patch because I don't have hardware to
  validate if my assumption about PIXEL_NONE-only is correct. Also, I
  added PREMULTI to the list of supported blend mode to avoid uAPI
  regressions since it was the required/default mode for many years and,
  without overlay plane, PIXEL_NONE and PREMULTI are equivalent for
  primary on top of a black blackground.

[1] https://lore.kernel.org/dri-devel/20260720215058.398210-3-lyude@redhat.com/

[v1]: https://lore.kernel.org/dri-devel/20260722183240.626522-1-mwen@igalia.com/
Changes:
- new patch for pixel_blend_mode default value other than PREMULTI.
- remove DCE11 which supports per_pixel_alpha but doesn't support DCN_UNIVERSAL_PLANE.
- new patch for the primary plane blend mode on DCE-generations

[v2]: https://lore.kernel.org/dri-devel/20260804140758.107683-1-mwen@igalia.com/
Changes:
- keep alpha property only for overlay planes (looks like primary plane
  doesn't actually support it) - alpha prop in primary planes causes IGT
  test failures with RX 7900 XT on a 4k60 HP U27 as reported by Daniel
  Wheeler.
- improve readability of if conditions (Alex H)
- add Leandro's r-b tags.

[v3]: https://lore.kernel.org/dri-devel/20260813143605.106104-1-mwen@igalia.com/
Changes:
- add Daniel's, Mikhail's and Viktor's tested-by tag, accordingly
- add Alex H r-b tag
- add PREMULTI to the DCE list of supported blend modes to avoid
  uAPI regression reported by Viktor.

Best Regards,

Melissa

Melissa Wen (3):
  drm/atomic-state-helper: set pixel_blend_mode to prop default on reset
  drm/amd/display: fix missing blend-mode-prop warning for DCN
  drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE

 .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 31 +++++++++++++++++--
 drivers/gpu/drm/drm_atomic_state_helper.c     |  7 +++++
 2 files changed, 35 insertions(+), 3 deletions(-)

-- 
2.53.0

[PATCH v4 1/3] drm/atomic-state-helper: set pixel_blend_mode to prop default on reset

[Melissa Wen]

In __drm_atomic_helper_plane_state_init(), pixel_blend_mode is always
reset to DRM_MODE_BLEND_PREMULTI. That was consistent while
drm_plane_create_blend_mode_property() required PREMULTI in the
supported modes, but it now falls back to COVERAGE or PIXEL_NONE when
the driver doesn't support PREMULTI. The hardcoded default may therefore
not be a blend mode the hardware can do, nor one the property
advertises.

Initialize pixel_blend_mode from the blend mode property default
instead, keeping DRM_MODE_BLEND_PREMULTI for planes without the
property.

Fixes: 9813e158d13d ("drm/drm_blend: allow blend mode property without PREMULTI")
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Reviewed-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Signed-off-by: Melissa Wen <mwen@igalia.com>
---
 drivers/gpu/drm/drm_atomic_state_helper.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
index d90d1d7c9cf9..a2ef272e9f27 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -278,7 +278,14 @@ void __drm_atomic_helper_plane_state_init(struct drm_plane_state *plane_state,
 	plane_state->rotation = DRM_MODE_ROTATE_0;
 
 	plane_state->alpha = DRM_BLEND_ALPHA_OPAQUE;
+
 	plane_state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
+	if (plane->blend_mode_property) {
+		if (!drm_object_property_get_default_value(&plane->base,
+							   plane->blend_mode_property,
+							   &val))
+			plane_state->pixel_blend_mode = val;
+	}
 
 	if (plane->color_encoding_property) {
 		if (!drm_object_property_get_default_value(&plane->base,
-- 
2.53.0

[PATCH v4 2/3] drm/amd/display: fix missing blend-mode-prop warning for DCN

[Melissa Wen]

validate_blend_mode_for_alpha_formats() warns when a plane supports
formats with alpha but doesn't expose the blend mode property. Fix this
by adding the same overlay plane blend modes to primary plane, since
they are all universal planes in DCN-generation. Cursor planes support
ARGB8888 format and CURSOR_MODE_COLOR_PRE_MULTIPLIED_ALPHA is set by
default (other color formats are not implemented), so only expose
support to PREMULTI, which is the default blend mode on DRM.

Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Reviewed-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Signed-off-by: Melissa Wen <mwen@igalia.com>

---
v3:
- keep primary planes w/o alpha property
- re-order if-conditions for readability
---
 .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 21 ++++++++++++++++---
 1 file changed, 18 insertions(+), 3 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 1b564cfe2120..ab9bbe8ca333 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
@@ -1923,16 +1923,31 @@ int amdgpu_dm_plane_init(struct amdgpu_display_manager *dm,
 	if (res)
 		return res;
 
-	if (plane->type == DRM_PLANE_TYPE_OVERLAY &&
-	    plane_cap && plane_cap->per_pixel_alpha) {
+	/* 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.
+	 */
+	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) {
 		unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
 					  BIT(DRM_MODE_BLEND_PREMULTI) |
 					  BIT(DRM_MODE_BLEND_COVERAGE);
 
-		drm_plane_create_alpha_property(plane);
 		drm_plane_create_blend_mode_property(plane, blend_caps);
+
+		if (plane->type == DRM_PLANE_TYPE_OVERLAY)
+			drm_plane_create_alpha_property(plane);
 	}
 
+	/* Cursor color format is set to CURSOR_MODE_COLOR_PRE_MULTIPLIED_ALPHA
+	 * by default, so only advertise DRM_MODE_BLEND_PREMULTI blend mode for
+	 * this type of plane.
+	 */
+	if (plane->type == DRM_PLANE_TYPE_CURSOR)
+		drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_PREMULTI));
+
 	if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
 		/*
 		 * Allow OVERLAY planes to be used as underlays by assigning an
-- 
2.53.0

[PATCH v4 3/3] drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE

[Melissa Wen]

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 and PREMULTI for primary planes. As long as the
background is black and there is no overlay plane, PIXEL_NONE and
PREMULTI are equivalent, and PREMULTI has been the mandatory/default
mode for years, so keep it to avoid regressions.

Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
Tested-by: Viktor Jägersküpper <viktor_jaegerskuepper@freenet.de>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com> #v3
Reviewed-by: Alex Hung <alex.hung@amd.com> #v3
Reviewed-by: Leandro Ribeiro <leandro.ribeiro@collabora.com> #v2
Signed-off-by: Melissa Wen <mwen@igalia.com>

---
v3:
- fix indentation (Alex H)
v4:
- add PREMULTI to avoid regression (reported by Viktor)
---
 .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 24 +++++++++++++------
 1 file changed, 17 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..402f0d333150 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 +1923,24 @@ 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 is
+	 * ignored across DCE versions. Keep PREMULTI to avoid uAPI
+	 * regressions: it was the default/mandatory mode for many years and,
+	 * with no overlay plane, primary composes on top of a black
+	 * background, where PREMULTI and PIXEL_NONE are equivalent.
 	 */
-	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) {
+		unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
+					  BIT(DRM_MODE_BLEND_PREMULTI);
+
+		drm_plane_create_blend_mode_property(plane, blend_caps);
+	} 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);
-- 
2.53.0

Re: [PATCH v4 3/3] drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE

[Melissa Wen]

On 26/08/2026 12:37, 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 and PREMULTI for primary planes. As long as the
> background is black and there is no overlay plane, PIXEL_NONE and
> PREMULTI are equivalent, and PREMULTI has been the mandatory/default
> mode for years, so keep it to avoid regressions.
>
> Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
> Tested-by: Viktor Jägersküpper <viktor_jaegerskuepper@freenet.de>
> Tested-by: Dan Wheeler <daniel.wheeler@amd.com> #v3
> Reviewed-by: Alex Hung <alex.hung@amd.com> #v3
> Reviewed-by: Leandro Ribeiro <leandro.ribeiro@collabora.com> #v2

Hi,

Only this patch changed in this v4, and it was only tested by Viktor.
As r-b tags came from previous version, can I get an ack/r-b to this one 
too?

Thanks,

Melissa

> Signed-off-by: Melissa Wen <mwen@igalia.com>
>
> ---
> v3:
> - fix indentation (Alex H)
> v4:
> - add PREMULTI to avoid regression (reported by Viktor)
> ---
>   .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 24 +++++++++++++------
>   1 file changed, 17 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..402f0d333150 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 +1923,24 @@ 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 is
> +	 * ignored across DCE versions. Keep PREMULTI to avoid uAPI
> +	 * regressions: it was the default/mandatory mode for many years and,
> +	 * with no overlay plane, primary composes on top of a black
> +	 * background, where PREMULTI and PIXEL_NONE are equivalent.
>   	 */
> -	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) {
> +		unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
> +					  BIT(DRM_MODE_BLEND_PREMULTI);
> +
> +		drm_plane_create_blend_mode_property(plane, blend_caps);
> +	} 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);

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Timur Kristóf]

On Wednesday, August 26, 2026 12:37:04 PM Central European Summer Time Melissa 
Wen wrote:
> PREMULTI was the default DRM blend mode until 9813e158d13d
> ("drm/drm_blend: allow blend mode property without PREMULTI") introduced
> the possibility of exposing the blend mode property without PREMULTI
> being supported. However, __drm_atomic_helper_plane_state_init() still
> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
> mode in this property. In the same series, 860e748bddcc ("drm: ensure
> blend mode supported if pixel format with alpha exposed") starts warning
> drivers that supports alpha formats in a given planes but doesn't
> support blend mode property, which includes AMD primary and cursor
> planes.
> 
> For AMD DCN families, overlay and primary planes support the three blend
> modes, and therefore PREMULTI is still the default mode. So the warning
> can be fixed by just creating blend mode properties for primary planes
> too. PREMULTI is the default/unique mode for cursor planes in DCN and
> DCE driver. However, looks like PIXEL_NONE is the unique blend mode
> supported by DCE-generation driver. I don't have the hardware to check
> it out, but looking at the code I understand that, even if the hardware
> can do PREMULTI or COVERAGE, the way it programs registers doesn't make
> these other blend modes actually available.

Hi Melissa,

Thanks for noticing and fixing this.
To make the code a bit easier to follow, I recommend moving the consideration 
for blending and alpha properties to a smaller helper function. That's just my 
personal preference though. The way you wrote it in the series is also good.

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>

> 
> Bearing this in mind, this series is organized as follow:
> 
> - Patch 1 fixes the pixel_blend_mode reset when the blend mode property
>   is advertised without PREMULTI support. It's needed for AMD
>   DCE-generation (patch 3) and I think with this we can also remove a
>   workaround in nouveau nv50_wndw_default_state() caused by the
>   hardcoded PREMULTI default value [1].
> 
> - Patch 2 fixes the missing-blend-mode-property warning for DCN primary
>   plane and for DCN+DCE cursor plane. The alpha property keeps only on
>   overlay planes because looks like this is not supported by AMD primary
>   planes and it doesn't affect the blend mode warning we are targetting.
>   Enabling alpha properties to primary was also causing -EINVAL on IGT
>   alpha tests because it started testing primary planes and disabling it
>   (which is not allowed by the AMD display driver).
> 
> - Patch 3 fixes the warning for DCE primary plane, but I detached this
>   solution from the previous patch because I don't have hardware to
>   validate if my assumption about PIXEL_NONE-only is correct. Also, I
>   added PREMULTI to the list of supported blend mode to avoid uAPI
>   regressions since it was the required/default mode for many years and,
>   without overlay plane, PIXEL_NONE and PREMULTI are equivalent for
>   primary on top of a black blackground.
> 
> [1]
> https://lore.kernel.org/dri-devel/20260720215058.398210-3-lyude@redhat.com/
> 
> [v1]:
> https://lore.kernel.org/dri-devel/20260722183240.626522-1-mwen@igalia.com/
> Changes:
> - new patch for pixel_blend_mode default value other than PREMULTI.
> - remove DCE11 which supports per_pixel_alpha but doesn't support
> DCN_UNIVERSAL_PLANE. - new patch for the primary plane blend mode on
> DCE-generations
> 
> [v2]:
> https://lore.kernel.org/dri-devel/20260804140758.107683-1-mwen@igalia.com/
> Changes:
> - keep alpha property only for overlay planes (looks like primary plane
>   doesn't actually support it) - alpha prop in primary planes causes IGT
>   test failures with RX 7900 XT on a 4k60 HP U27 as reported by Daniel
>   Wheeler.
> - improve readability of if conditions (Alex H)
> - add Leandro's r-b tags.
> 
> [v3]:
> https://lore.kernel.org/dri-devel/20260813143605.106104-1-mwen@igalia.com/
> Changes:
> - add Daniel's, Mikhail's and Viktor's tested-by tag, accordingly
> - add Alex H r-b tag
> - add PREMULTI to the DCE list of supported blend modes to avoid
>   uAPI regression reported by Viktor.
> 
> Best Regards,
> 
> Melissa
> 
> Melissa Wen (3):
>   drm/atomic-state-helper: set pixel_blend_mode to prop default on reset
>   drm/amd/display: fix missing blend-mode-prop warning for DCN
>   drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE
> 
>  .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 31 +++++++++++++++++--
>  drivers/gpu/drm/drm_atomic_state_helper.c     |  7 +++++
>  2 files changed, 35 insertions(+), 3 deletions(-)

Re: [PATCH v4 3/3] drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE

[Alex Hung]

Reviewed-by: Alex Hung <alex.hung@amd.com>

On 8/26/26 04:37, 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 and PREMULTI for primary planes. As long as the
> background is black and there is no overlay plane, PIXEL_NONE and
> PREMULTI are equivalent, and PREMULTI has been the mandatory/default
> mode for years, so keep it to avoid regressions.
> 
> Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
> Tested-by: Viktor Jägersküpper <viktor_jaegerskuepper@freenet.de>
> Tested-by: Dan Wheeler <daniel.wheeler@amd.com> #v3
> Reviewed-by: Alex Hung <alex.hung@amd.com> #v3
> Reviewed-by: Leandro Ribeiro <leandro.ribeiro@collabora.com> #v2
> Signed-off-by: Melissa Wen <mwen@igalia.com>
> 
> ---
> v3:
> - fix indentation (Alex H)
> v4:
> - add PREMULTI to avoid regression (reported by Viktor)
> ---
>   .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 24 +++++++++++++------
>   1 file changed, 17 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..402f0d333150 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 +1923,24 @@ 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 is
> +	 * ignored across DCE versions. Keep PREMULTI to avoid uAPI
> +	 * regressions: it was the default/mandatory mode for many years and,
> +	 * with no overlay plane, primary composes on top of a black
> +	 * background, where PREMULTI and PIXEL_NONE are equivalent.
>   	 */
> -	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) {
> +		unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
> +					  BIT(DRM_MODE_BLEND_PREMULTI);
> +
> +		drm_plane_create_blend_mode_property(plane, blend_caps);
> +	} 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);

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Alex Deucher]

On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
>
> PREMULTI was the default DRM blend mode until 9813e158d13d
> ("drm/drm_blend: allow blend mode property without PREMULTI") introduced
> the possibility of exposing the blend mode property without PREMULTI
> being supported. However, __drm_atomic_helper_plane_state_init() still
> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
> mode in this property. In the same series, 860e748bddcc ("drm: ensure
> blend mode supported if pixel format with alpha exposed") starts warning
> drivers that supports alpha formats in a given planes but doesn't
> support blend mode property, which includes AMD primary and cursor
> planes.
>
> For AMD DCN families, overlay and primary planes support the three blend
> modes, and therefore PREMULTI is still the default mode. So the warning
> can be fixed by just creating blend mode properties for primary planes
> too. PREMULTI is the default/unique mode for cursor planes in DCN and
> DCE driver. However, looks like PIXEL_NONE is the unique blend mode
> supported by DCE-generation driver. I don't have the hardware to check
> it out, but looking at the code I understand that, even if the hardware
> can do PREMULTI or COVERAGE, the way it programs registers doesn't make
> these other blend modes actually available.
>
> Bearing this in mind, this series is organized as follow:
>
> - Patch 1 fixes the pixel_blend_mode reset when the blend mode property
>   is advertised without PREMULTI support. It's needed for AMD
>   DCE-generation (patch 3) and I think with this we can also remove a
>   workaround in nouveau nv50_wndw_default_state() caused by the
>   hardcoded PREMULTI default value [1].
>
> - Patch 2 fixes the missing-blend-mode-property warning for DCN primary
>   plane and for DCN+DCE cursor plane. The alpha property keeps only on
>   overlay planes because looks like this is not supported by AMD primary
>   planes and it doesn't affect the blend mode warning we are targetting.
>   Enabling alpha properties to primary was also causing -EINVAL on IGT
>   alpha tests because it started testing primary planes and disabling it
>   (which is not allowed by the AMD display driver).
>
> - Patch 3 fixes the warning for DCE primary plane, but I detached this
>   solution from the previous patch because I don't have hardware to
>   validate if my assumption about PIXEL_NONE-only is correct. Also, I
>   added PREMULTI to the list of supported blend mode to avoid uAPI
>   regressions since it was the required/default mode for many years and,
>   without overlay plane, PIXEL_NONE and PREMULTI are equivalent for
>   primary on top of a black blackground.
>

I presume you are planning to apply this directly to drm-misc for 7.3?

Thanks,

Alex

> [1] https://lore.kernel.org/dri-devel/20260720215058.398210-3-lyude@redhat.com/
>
> [v1]: https://lore.kernel.org/dri-devel/20260722183240.626522-1-mwen@igalia.com/
> Changes:
> - new patch for pixel_blend_mode default value other than PREMULTI.
> - remove DCE11 which supports per_pixel_alpha but doesn't support DCN_UNIVERSAL_PLANE.
> - new patch for the primary plane blend mode on DCE-generations
>
> [v2]: https://lore.kernel.org/dri-devel/20260804140758.107683-1-mwen@igalia.com/
> Changes:
> - keep alpha property only for overlay planes (looks like primary plane
>   doesn't actually support it) - alpha prop in primary planes causes IGT
>   test failures with RX 7900 XT on a 4k60 HP U27 as reported by Daniel
>   Wheeler.
> - improve readability of if conditions (Alex H)
> - add Leandro's r-b tags.
>
> [v3]: https://lore.kernel.org/dri-devel/20260813143605.106104-1-mwen@igalia.com/
> Changes:
> - add Daniel's, Mikhail's and Viktor's tested-by tag, accordingly
> - add Alex H r-b tag
> - add PREMULTI to the DCE list of supported blend modes to avoid
>   uAPI regression reported by Viktor.
>
> Best Regards,
>
> Melissa
>
> Melissa Wen (3):
>   drm/atomic-state-helper: set pixel_blend_mode to prop default on reset
>   drm/amd/display: fix missing blend-mode-prop warning for DCN
>   drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE
>
>  .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 31 +++++++++++++++++--
>  drivers/gpu/drm/drm_atomic_state_helper.c     |  7 +++++
>  2 files changed, 35 insertions(+), 3 deletions(-)
>
> --
> 2.53.0
>

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Melissa Wen]

On 27/08/2026 15:34, Alex Deucher wrote:
> On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
>> PREMULTI was the default DRM blend mode until 9813e158d13d
>> ("drm/drm_blend: allow blend mode property without PREMULTI") introduced
>> the possibility of exposing the blend mode property without PREMULTI
>> being supported. However, __drm_atomic_helper_plane_state_init() still
>> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
>> mode in this property. In the same series, 860e748bddcc ("drm: ensure
>> blend mode supported if pixel format with alpha exposed") starts warning
>> drivers that supports alpha formats in a given planes but doesn't
>> support blend mode property, which includes AMD primary and cursor
>> planes.
>>
>> For AMD DCN families, overlay and primary planes support the three blend
>> modes, and therefore PREMULTI is still the default mode. So the warning
>> can be fixed by just creating blend mode properties for primary planes
>> too. PREMULTI is the default/unique mode for cursor planes in DCN and
>> DCE driver. However, looks like PIXEL_NONE is the unique blend mode
>> supported by DCE-generation driver. I don't have the hardware to check
>> it out, but looking at the code I understand that, even if the hardware
>> can do PREMULTI or COVERAGE, the way it programs registers doesn't make
>> these other blend modes actually available.
>>
>> Bearing this in mind, this series is organized as follow:
>>
>> - Patch 1 fixes the pixel_blend_mode reset when the blend mode property
>>    is advertised without PREMULTI support. It's needed for AMD
>>    DCE-generation (patch 3) and I think with this we can also remove a
>>    workaround in nouveau nv50_wndw_default_state() caused by the
>>    hardcoded PREMULTI default value [1].
>>
>> - Patch 2 fixes the missing-blend-mode-property warning for DCN primary
>>    plane and for DCN+DCE cursor plane. The alpha property keeps only on
>>    overlay planes because looks like this is not supported by AMD primary
>>    planes and it doesn't affect the blend mode warning we are targetting.
>>    Enabling alpha properties to primary was also causing -EINVAL on IGT
>>    alpha tests because it started testing primary planes and disabling it
>>    (which is not allowed by the AMD display driver).
>>
>> - Patch 3 fixes the warning for DCE primary plane, but I detached this
>>    solution from the previous patch because I don't have hardware to
>>    validate if my assumption about PIXEL_NONE-only is correct. Also, I
>>    added PREMULTI to the list of supported blend mode to avoid uAPI
>>    regressions since it was the required/default mode for many years and,
>>    without overlay plane, PIXEL_NONE and PREMULTI are equivalent for
>>    primary on top of a black blackground.
>>
> I presume you are planning to apply this directly to drm-misc for 7.3?

Right, I'll apply to drm-misc-fixes, just doing it now.

Best Regards,

Melissa

>
> Thanks,
>
> Alex
>
>> [1] https://lore.kernel.org/dri-devel/20260720215058.398210-3-lyude@redhat.com/
>>
>> [v1]: https://lore.kernel.org/dri-devel/20260722183240.626522-1-mwen@igalia.com/
>> Changes:
>> - new patch for pixel_blend_mode default value other than PREMULTI.
>> - remove DCE11 which supports per_pixel_alpha but doesn't support DCN_UNIVERSAL_PLANE.
>> - new patch for the primary plane blend mode on DCE-generations
>>
>> [v2]: https://lore.kernel.org/dri-devel/20260804140758.107683-1-mwen@igalia.com/
>> Changes:
>> - keep alpha property only for overlay planes (looks like primary plane
>>    doesn't actually support it) - alpha prop in primary planes causes IGT
>>    test failures with RX 7900 XT on a 4k60 HP U27 as reported by Daniel
>>    Wheeler.
>> - improve readability of if conditions (Alex H)
>> - add Leandro's r-b tags.
>>
>> [v3]: https://lore.kernel.org/dri-devel/20260813143605.106104-1-mwen@igalia.com/
>> Changes:
>> - add Daniel's, Mikhail's and Viktor's tested-by tag, accordingly
>> - add Alex H r-b tag
>> - add PREMULTI to the DCE list of supported blend modes to avoid
>>    uAPI regression reported by Viktor.
>>
>> Best Regards,
>>
>> Melissa
>>
>> Melissa Wen (3):
>>    drm/atomic-state-helper: set pixel_blend_mode to prop default on reset
>>    drm/amd/display: fix missing blend-mode-prop warning for DCN
>>    drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE
>>
>>   .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 31 +++++++++++++++++--
>>   drivers/gpu/drm/drm_atomic_state_helper.c     |  7 +++++
>>   2 files changed, 35 insertions(+), 3 deletions(-)
>>
>> --
>> 2.53.0
>>

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Melissa Wen]

On 27/08/2026 18:37, Melissa Wen wrote:
>
>
> On 27/08/2026 15:34, Alex Deucher wrote:
>> On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
>>> PREMULTI was the default DRM blend mode until 9813e158d13d
>>> ("drm/drm_blend: allow blend mode property without PREMULTI") 
>>> introduced
>>> the possibility of exposing the blend mode property without PREMULTI
>>> being supported. However, __drm_atomic_helper_plane_state_init() still
>>> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
>>> mode in this property. In the same series, 860e748bddcc ("drm: ensure
>>> blend mode supported if pixel format with alpha exposed") starts 
>>> warning
>>> drivers that supports alpha formats in a given planes but doesn't
>>> support blend mode property, which includes AMD primary and cursor
>>> planes.
>>>
>>> For AMD DCN families, overlay and primary planes support the three 
>>> blend
>>> modes, and therefore PREMULTI is still the default mode. So the warning
>>> can be fixed by just creating blend mode properties for primary planes
>>> too. PREMULTI is the default/unique mode for cursor planes in DCN and
>>> DCE driver. However, looks like PIXEL_NONE is the unique blend mode
>>> supported by DCE-generation driver. I don't have the hardware to check
>>> it out, but looking at the code I understand that, even if the hardware
>>> can do PREMULTI or COVERAGE, the way it programs registers doesn't make
>>> these other blend modes actually available.
>>>
>>> Bearing this in mind, this series is organized as follow:
>>>
>>> - Patch 1 fixes the pixel_blend_mode reset when the blend mode property
>>>    is advertised without PREMULTI support. It's needed for AMD
>>>    DCE-generation (patch 3) and I think with this we can also remove a
>>>    workaround in nouveau nv50_wndw_default_state() caused by the
>>>    hardcoded PREMULTI default value [1].
>>>
>>> - Patch 2 fixes the missing-blend-mode-property warning for DCN primary
>>>    plane and for DCN+DCE cursor plane. The alpha property keeps only on
>>>    overlay planes because looks like this is not supported by AMD 
>>> primary
>>>    planes and it doesn't affect the blend mode warning we are 
>>> targetting.
>>>    Enabling alpha properties to primary was also causing -EINVAL on IGT
>>>    alpha tests because it started testing primary planes and 
>>> disabling it
>>>    (which is not allowed by the AMD display driver).
>>>
>>> - Patch 3 fixes the warning for DCE primary plane, but I detached this
>>>    solution from the previous patch because I don't have hardware to
>>>    validate if my assumption about PIXEL_NONE-only is correct. Also, I
>>>    added PREMULTI to the list of supported blend mode to avoid uAPI
>>>    regressions since it was the required/default mode for many years 
>>> and,
>>>    without overlay plane, PIXEL_NONE and PREMULTI are equivalent for
>>>    primary on top of a black blackground.
>>>
>> I presume you are planning to apply this directly to drm-misc for 7.3?
>
> Right, I'll apply to drm-misc-fixes, just doing it now.

Or not now. I have to wait for -rc1.
I'll keep it on my radar.

Melissa

>
> Best Regards,
>
> Melissa
>
>>
>> Thanks,
>>
>> Alex
>>
>>> [1] 
>>> https://lore.kernel.org/dri-devel/20260720215058.398210-3-lyude@redhat.com/
>>>
>>> [v1]: 
>>> https://lore.kernel.org/dri-devel/20260722183240.626522-1-mwen@igalia.com/
>>> Changes:
>>> - new patch for pixel_blend_mode default value other than PREMULTI.
>>> - remove DCE11 which supports per_pixel_alpha but doesn't support 
>>> DCN_UNIVERSAL_PLANE.
>>> - new patch for the primary plane blend mode on DCE-generations
>>>
>>> [v2]: 
>>> https://lore.kernel.org/dri-devel/20260804140758.107683-1-mwen@igalia.com/
>>> Changes:
>>> - keep alpha property only for overlay planes (looks like primary plane
>>>    doesn't actually support it) - alpha prop in primary planes 
>>> causes IGT
>>>    test failures with RX 7900 XT on a 4k60 HP U27 as reported by Daniel
>>>    Wheeler.
>>> - improve readability of if conditions (Alex H)
>>> - add Leandro's r-b tags.
>>>
>>> [v3]: 
>>> https://lore.kernel.org/dri-devel/20260813143605.106104-1-mwen@igalia.com/
>>> Changes:
>>> - add Daniel's, Mikhail's and Viktor's tested-by tag, accordingly
>>> - add Alex H r-b tag
>>> - add PREMULTI to the DCE list of supported blend modes to avoid
>>>    uAPI regression reported by Viktor.
>>>
>>> Best Regards,
>>>
>>> Melissa
>>>
>>> Melissa Wen (3):
>>>    drm/atomic-state-helper: set pixel_blend_mode to prop default on 
>>> reset
>>>    drm/amd/display: fix missing blend-mode-prop warning for DCN
>>>    drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for 
>>> DCE
>>>
>>>   .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 31 
>>> +++++++++++++++++--
>>>   drivers/gpu/drm/drm_atomic_state_helper.c     |  7 +++++
>>>   2 files changed, 35 insertions(+), 3 deletions(-)
>>>
>>> -- 
>>> 2.53.0
>>>
>

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Melissa Wen]

On 26/08/2026 18:49, Timur Kristóf wrote:
> On Wednesday, August 26, 2026 12:37:04 PM Central European Summer Time Melissa
> Wen wrote:
>> PREMULTI was the default DRM blend mode until 9813e158d13d
>> ("drm/drm_blend: allow blend mode property without PREMULTI") introduced
>> the possibility of exposing the blend mode property without PREMULTI
>> being supported. However, __drm_atomic_helper_plane_state_init() still
>> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
>> mode in this property. In the same series, 860e748bddcc ("drm: ensure
>> blend mode supported if pixel format with alpha exposed") starts warning
>> drivers that supports alpha formats in a given planes but doesn't
>> support blend mode property, which includes AMD primary and cursor
>> planes.
>>
>> For AMD DCN families, overlay and primary planes support the three blend
>> modes, and therefore PREMULTI is still the default mode. So the warning
>> can be fixed by just creating blend mode properties for primary planes
>> too. PREMULTI is the default/unique mode for cursor planes in DCN and
>> DCE driver. However, looks like PIXEL_NONE is the unique blend mode
>> supported by DCE-generation driver. I don't have the hardware to check
>> it out, but looking at the code I understand that, even if the hardware
>> can do PREMULTI or COVERAGE, the way it programs registers doesn't make
>> these other blend modes actually available.
> Hi Melissa,
>
> Thanks for noticing and fixing this.
> To make the code a bit easier to follow, I recommend moving the consideration
> for blending and alpha properties to a smaller helper function. That's just my
> personal preference though. The way you wrote it in the series is also good.

Hey,

I agree with your recommendation.
I'll do this helper in a follow-up patch, and ask you to help me testing 
it :)

Thanks!

Melissa


>
> Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
>
>> Bearing this in mind, this series is organized as follow:
>>
>> - Patch 1 fixes the pixel_blend_mode reset when the blend mode property
>>    is advertised without PREMULTI support. It's needed for AMD
>>    DCE-generation (patch 3) and I think with this we can also remove a
>>    workaround in nouveau nv50_wndw_default_state() caused by the
>>    hardcoded PREMULTI default value [1].
>>
>> - Patch 2 fixes the missing-blend-mode-property warning for DCN primary
>>    plane and for DCN+DCE cursor plane. The alpha property keeps only on
>>    overlay planes because looks like this is not supported by AMD primary
>>    planes and it doesn't affect the blend mode warning we are targetting.
>>    Enabling alpha properties to primary was also causing -EINVAL on IGT
>>    alpha tests because it started testing primary planes and disabling it
>>    (which is not allowed by the AMD display driver).
>>
>> - Patch 3 fixes the warning for DCE primary plane, but I detached this
>>    solution from the previous patch because I don't have hardware to
>>    validate if my assumption about PIXEL_NONE-only is correct. Also, I
>>    added PREMULTI to the list of supported blend mode to avoid uAPI
>>    regressions since it was the required/default mode for many years and,
>>    without overlay plane, PIXEL_NONE and PREMULTI are equivalent for
>>    primary on top of a black blackground.
>>
>> [1]
>> https://lore.kernel.org/dri-devel/20260720215058.398210-3-lyude@redhat.com/
>>
>> [v1]:
>> https://lore.kernel.org/dri-devel/20260722183240.626522-1-mwen@igalia.com/
>> Changes:
>> - new patch for pixel_blend_mode default value other than PREMULTI.
>> - remove DCE11 which supports per_pixel_alpha but doesn't support
>> DCN_UNIVERSAL_PLANE. - new patch for the primary plane blend mode on
>> DCE-generations
>>
>> [v2]:
>> https://lore.kernel.org/dri-devel/20260804140758.107683-1-mwen@igalia.com/
>> Changes:
>> - keep alpha property only for overlay planes (looks like primary plane
>>    doesn't actually support it) - alpha prop in primary planes causes IGT
>>    test failures with RX 7900 XT on a 4k60 HP U27 as reported by Daniel
>>    Wheeler.
>> - improve readability of if conditions (Alex H)
>> - add Leandro's r-b tags.
>>
>> [v3]:
>> https://lore.kernel.org/dri-devel/20260813143605.106104-1-mwen@igalia.com/
>> Changes:
>> - add Daniel's, Mikhail's and Viktor's tested-by tag, accordingly
>> - add Alex H r-b tag
>> - add PREMULTI to the DCE list of supported blend modes to avoid
>>    uAPI regression reported by Viktor.
>>
>> Best Regards,
>>
>> Melissa
>>
>> Melissa Wen (3):
>>    drm/atomic-state-helper: set pixel_blend_mode to prop default on reset
>>    drm/amd/display: fix missing blend-mode-prop warning for DCN
>>    drm/amd/display: advertise PIXEL_NONE and PREMULTI blend mode for DCE
>>
>>   .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   | 31 +++++++++++++++++--
>>   drivers/gpu/drm/drm_atomic_state_helper.c     |  7 +++++
>>   2 files changed, 35 insertions(+), 3 deletions(-)
>
>
>

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Thorsten Leemhuis]

On 8/27/26 19:14, Melissa Wen wrote:
> On 27/08/2026 18:37, Melissa Wen wrote:
>> On 27/08/2026 15:34, Alex Deucher wrote:
>>> On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
>>>> PREMULTI was the default DRM blend mode until 9813e158d13d
>>>> ("drm/drm_blend: allow blend mode property without PREMULTI")
>>>> introduced
>>>> the possibility of exposing the blend mode property without PREMULTI
>>>> being supported. However, __drm_atomic_helper_plane_state_init() still
>>>> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
>>>> mode in this property. In the same series, 860e748bddcc ("drm: ensure
>>>> blend mode supported if pixel format with alpha exposed") starts
>>>> warning
>>>> drivers that supports alpha formats in a given planes but doesn't
>>>> support blend mode property, which includes AMD primary and cursor
>>>> planes.
> [...]
>>> I presume you are planning to apply this directly to drm-misc for 7.3?
>>
>> Right, I'll apply to drm-misc-fixes, just doing it now.
> 
> Or not now. I have to wait for -rc1.
> I'll keep it on my radar.
Hmmm, that sounds like these fixes will miss -rc1. But wouldn't it be
good to get them included there, as they afaik (please correct me if I'm
wrong, is easy to mix something up from the outside!) the warnings that
Greg described as ""It's not good to boot and have a bunch of warnings
already happening, resulting in a "tainted" kernel before I have the
chance to break anything manually myself...""[1], as more people then
will likely encounter this (and then waste time on bisecting an issue
known for weeks for which a fix exists).

Ciao, Thorsten

[1]
https://lore.kernel.org/all/2026082651-spinning-cornbread-33ba@gregkh/

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Viktor Jägersküpper]

On 8/28/26 09:22, Thorsten Leemhuis wrote:
> On 8/27/26 19:14, Melissa Wen wrote:
>> On 27/08/2026 18:37, Melissa Wen wrote:
>>> On 27/08/2026 15:34, Alex Deucher wrote:
>>>> On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
>>>>> PREMULTI was the default DRM blend mode until 9813e158d13d
>>>>> ("drm/drm_blend: allow blend mode property without PREMULTI")
>>>>> introduced
>>>>> the possibility of exposing the blend mode property without PREMULTI
>>>>> being supported. However, __drm_atomic_helper_plane_state_init() still
>>>>> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
>>>>> mode in this property. In the same series, 860e748bddcc ("drm: ensure
>>>>> blend mode supported if pixel format with alpha exposed") starts
>>>>> warning
>>>>> drivers that supports alpha formats in a given planes but doesn't
>>>>> support blend mode property, which includes AMD primary and cursor
>>>>> planes.
>> [...]
>>>> I presume you are planning to apply this directly to drm-misc for 7.3?
>>>
>>> Right, I'll apply to drm-misc-fixes, just doing it now.
>>
>> Or not now. I have to wait for -rc1.
>> I'll keep it on my radar.
> Hmmm, that sounds like these fixes will miss -rc1. But wouldn't it be
> good to get them included there, as they afaik (please correct me if I'm
> wrong, is easy to mix something up from the outside!) the warnings that
> Greg described as ""It's not good to boot and have a bunch of warnings
> already happening, resulting in a "tainted" kernel before I have the
> chance to break anything manually myself...""[1], as more people then
> will likely encounter this (and then waste time on bisecting an issue
> known for weeks for which a fix exists).
> 
> Ciao, Thorsten
> 
> [1]
> https://lore.kernel.org/all/2026082651-spinning-cornbread-33ba@gregkh/

If I understand correctly, the *actual* fix (for all affected drivers)
will make it into 7.3-rc1, see this answer to my question:
https://lore.kernel.org/dri-devel/20260826-brave-nyala-of-elevation-d23aea@houat/

This fix is queued in drm-next:
https://gitlab.freedesktop.org/drm/kernel/-/commit/271e90eb5f9ff34951647e5ed33c1775eebcca50

It seems the drm-next branch is used for fixes arriving during the
merge window, which might be confusing for outsiders.

I hope that clears up the confusion.

Viktor

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Thorsten Leemhuis]

On 8/28/26 14:19, Viktor Jägersküpper wrote:
> On 8/28/26 09:22, Thorsten Leemhuis wrote:
>> On 8/27/26 19:14, Melissa Wen wrote:
>>> On 27/08/2026 18:37, Melissa Wen wrote:
>>>> On 27/08/2026 15:34, Alex Deucher wrote:
>>>>> On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
>>>>>> PREMULTI was the default DRM blend mode until 9813e158d13d
>>>>>> ("drm/drm_blend: allow blend mode property without PREMULTI")
>>>>>> introduced
>>>>>> the possibility of exposing the blend mode property without PREMULTI
>>>>>> being supported. However, __drm_atomic_helper_plane_state_init() still
>>>>>> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
>>>>>> mode in this property. In the same series, 860e748bddcc ("drm: ensure
>>>>>> blend mode supported if pixel format with alpha exposed") starts
>>>>>> warning
>>>>>> drivers that supports alpha formats in a given planes but doesn't
>>>>>> support blend mode property, which includes AMD primary and cursor
>>>>>> planes.
>>> [...]
>>>>> I presume you are planning to apply this directly to drm-misc for 7.3?
>>>>
>>>> Right, I'll apply to drm-misc-fixes, just doing it now.
>>>
>>> Or not now. I have to wait for -rc1.
>>> I'll keep it on my radar.
>> Hmmm, that sounds like these fixes will miss -rc1. But wouldn't it be
>> good to get them included there, as they afaik (please correct me if I'm
>> wrong, is easy to mix something up from the outside!) the warnings that
>> Greg described as ""It's not good to boot and have a bunch of warnings
>> already happening, resulting in a "tainted" kernel before I have the
>> chance to break anything manually myself...""[1], as more people then
>> will likely encounter this (and then waste time on bisecting an issue
>> known for weeks for which a fix exists).
>>
>> [1]
>> https://lore.kernel.org/all/2026082651-spinning-cornbread-33ba@gregkh/
> 
> If I understand correctly, the *actual* fix (for all affected drivers)
> will make it into 7.3-rc1, see this answer to my question:
> https://lore.kernel.org/dri-devel/20260826-brave-nyala-of-elevation-d23aea@houat/
>
> This fix is queued in drm-next:
> https://gitlab.freedesktop.org/drm/kernel/-/commit/271e90eb5f9ff34951647e5ed33c1775eebcca50

Ahh, yeah, many thx, I had see this downgrade to drm_warn() (which made
it to -rc1, yeah \o/), but had not made the right connections. :-/

FWIW, even with that done there is now one amdgpu regression report
about this already post-rc1:
https://lore.kernel.org/all/CANkdJ2VvJQSBzyOq=LgSW1=Z8-YiN_r9Py2iJ0UJDo55+dbfuA@mail.gmail.com/

"""
[...] After updating from kernel v7.2.2 to v7.3-rc1, several DRM plane
warnings regarding unset blend modes for pixel formats with alpha
channels started appearing in dmesg during initialization.

[drm] [PLANE:44:plane-0] pixel format with alpha exposed but blend
mode not setup. Please fix. [...]
"""

Will reply there now. Wondering if we need to do something about that if
more reports like that show up, but let's wait if that's the case.

Ciao, Thorsten

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Melissa Wen]

On 01/09/2026 09:12, Thorsten Leemhuis wrote:
> On 8/28/26 14:19, Viktor Jägersküpper wrote:
>> On 8/28/26 09:22, Thorsten Leemhuis wrote:
>>> On 8/27/26 19:14, Melissa Wen wrote:
>>>> On 27/08/2026 18:37, Melissa Wen wrote:
>>>>> On 27/08/2026 15:34, Alex Deucher wrote:
>>>>>> On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
>>>>>>> PREMULTI was the default DRM blend mode until 9813e158d13d
>>>>>>> ("drm/drm_blend: allow blend mode property without PREMULTI")
>>>>>>> introduced
>>>>>>> the possibility of exposing the blend mode property without PREMULTI
>>>>>>> being supported. However, __drm_atomic_helper_plane_state_init() still
>>>>>>> resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
>>>>>>> mode in this property. In the same series, 860e748bddcc ("drm: ensure
>>>>>>> blend mode supported if pixel format with alpha exposed") starts
>>>>>>> warning
>>>>>>> drivers that supports alpha formats in a given planes but doesn't
>>>>>>> support blend mode property, which includes AMD primary and cursor
>>>>>>> planes.
>>>> [...]
>>>>>> I presume you are planning to apply this directly to drm-misc for 7.3?
>>>>> Right, I'll apply to drm-misc-fixes, just doing it now.
>>>> Or not now. I have to wait for -rc1.
>>>> I'll keep it on my radar.
>>> Hmmm, that sounds like these fixes will miss -rc1. But wouldn't it be
>>> good to get them included there, as they afaik (please correct me if I'm
>>> wrong, is easy to mix something up from the outside!) the warnings that
>>> Greg described as ""It's not good to boot and have a bunch of warnings
>>> already happening, resulting in a "tainted" kernel before I have the
>>> chance to break anything manually myself...""[1], as more people then
>>> will likely encounter this (and then waste time on bisecting an issue
>>> known for weeks for which a fix exists).
>>>
>>> [1]
>>> https://lore.kernel.org/all/2026082651-spinning-cornbread-33ba@gregkh/
>> If I understand correctly, the *actual* fix (for all affected drivers)
>> will make it into 7.3-rc1, see this answer to my question:
>> https://lore.kernel.org/dri-devel/20260826-brave-nyala-of-elevation-d23aea@houat/
>>
>> This fix is queued in drm-next:
>> https://gitlab.freedesktop.org/drm/kernel/-/commit/271e90eb5f9ff34951647e5ed33c1775eebcca50
> Ahh, yeah, many thx, I had see this downgrade to drm_warn() (which made
> it to -rc1, yeah \o/), but had not made the right connections. :-/
>
> FWIW, even with that done there is now one amdgpu regression report
> about this already post-rc1:
> https://lore.kernel.org/all/CANkdJ2VvJQSBzyOq=LgSW1=Z8-YiN_r9Py2iJ0UJDo55+dbfuA@mail.gmail.com/
>
> """
> [...] After updating from kernel v7.2.2 to v7.3-rc1, several DRM plane
> warnings regarding unset blend modes for pixel formats with alpha
> channels started appearing in dmesg during initialization.
>
> [drm] [PLANE:44:plane-0] pixel format with alpha exposed but blend
> mode not setup. Please fix. [...]
> """
>
> Will reply there now. Wondering if we need to do something about that if
> more reports like that show up, but let's wait if that's the case.

I just applied this series to drm-misc-fixes:
- c3080b58d81d ("drm/atomic-state-helper: set pixel_blend_mode to prop 
default on reset")
- f0c75da0a6b4 ("drm/amd/display: fix missing blend-mode-prop warning 
for DCN")
- 332ad707e38f ("drm/amd/display: advertise PIXEL_NONE and PREMULTI 
blend mode for DCE")

With this, the dmesg message will no longer appear on the AMD driver.

Melissa

>
> Ciao, Thorsten

Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Greg KH]

On Wed, Sep 02, 2026 at 08:58:37PM +0200, Melissa Wen wrote:
> 
> 
> On 01/09/2026 09:12, Thorsten Leemhuis wrote:
> > On 8/28/26 14:19, Viktor Jägersküpper wrote:
> > > On 8/28/26 09:22, Thorsten Leemhuis wrote:
> > > > On 8/27/26 19:14, Melissa Wen wrote:
> > > > > On 27/08/2026 18:37, Melissa Wen wrote:
> > > > > > On 27/08/2026 15:34, Alex Deucher wrote:
> > > > > > > On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
> > > > > > > > PREMULTI was the default DRM blend mode until 9813e158d13d
> > > > > > > > ("drm/drm_blend: allow blend mode property without PREMULTI")
> > > > > > > > introduced
> > > > > > > > the possibility of exposing the blend mode property without PREMULTI
> > > > > > > > being supported. However, __drm_atomic_helper_plane_state_init() still
> > > > > > > > resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
> > > > > > > > mode in this property. In the same series, 860e748bddcc ("drm: ensure
> > > > > > > > blend mode supported if pixel format with alpha exposed") starts
> > > > > > > > warning
> > > > > > > > drivers that supports alpha formats in a given planes but doesn't
> > > > > > > > support blend mode property, which includes AMD primary and cursor
> > > > > > > > planes.
> > > > > [...]
> > > > > > > I presume you are planning to apply this directly to drm-misc for 7.3?
> > > > > > Right, I'll apply to drm-misc-fixes, just doing it now.
> > > > > Or not now. I have to wait for -rc1.
> > > > > I'll keep it on my radar.
> > > > Hmmm, that sounds like these fixes will miss -rc1. But wouldn't it be
> > > > good to get them included there, as they afaik (please correct me if I'm
> > > > wrong, is easy to mix something up from the outside!) the warnings that
> > > > Greg described as ""It's not good to boot and have a bunch of warnings
> > > > already happening, resulting in a "tainted" kernel before I have the
> > > > chance to break anything manually myself...""[1], as more people then
> > > > will likely encounter this (and then waste time on bisecting an issue
> > > > known for weeks for which a fix exists).
> > > > 
> > > > [1]
> > > > https://lore.kernel.org/all/2026082651-spinning-cornbread-33ba@gregkh/
> > > If I understand correctly, the *actual* fix (for all affected drivers)
> > > will make it into 7.3-rc1, see this answer to my question:
> > > https://lore.kernel.org/dri-devel/20260826-brave-nyala-of-elevation-d23aea@houat/
> > > 
> > > This fix is queued in drm-next:
> > > https://gitlab.freedesktop.org/drm/kernel/-/commit/271e90eb5f9ff34951647e5ed33c1775eebcca50
> > Ahh, yeah, many thx, I had see this downgrade to drm_warn() (which made
> > it to -rc1, yeah \o/), but had not made the right connections. :-/
> > 
> > FWIW, even with that done there is now one amdgpu regression report
> > about this already post-rc1:
> > https://lore.kernel.org/all/CANkdJ2VvJQSBzyOq=LgSW1=Z8-YiN_r9Py2iJ0UJDo55+dbfuA@mail.gmail.com/
> > 
> > """
> > [...] After updating from kernel v7.2.2 to v7.3-rc1, several DRM plane
> > warnings regarding unset blend modes for pixel formats with alpha
> > channels started appearing in dmesg during initialization.
> > 
> > [drm] [PLANE:44:plane-0] pixel format with alpha exposed but blend
> > mode not setup. Please fix. [...]
> > """
> > 
> > Will reply there now. Wondering if we need to do something about that if
> > more reports like that show up, but let's wait if that's the case.
> 
> I just applied this series to drm-misc-fixes:
> - c3080b58d81d ("drm/atomic-state-helper: set pixel_blend_mode to prop
> default on reset")
> - f0c75da0a6b4 ("drm/amd/display: fix missing blend-mode-prop warning for
> DCN")
> - 332ad707e38f ("drm/amd/display: advertise PIXEL_NONE and PREMULTI blend
> mode for DCE")
> 
> With this, the dmesg message will no longer appear on the AMD driver.

Great, thanks!