Re: [PATCH 4/4] Documentation/gpu/amdgpu/amdgpu_dm: add DM docs for pixel blend mode
On 07/17, Tales Lelo da Aparecida wrote: > On 16/07/2022 19:25, Melissa Wen wrote: > > AMD GPU display manager (DM) maps DRM pixel blend modes (None, > > Pre-multiplied, Coverage) to MPC hw blocks through blend configuration > > options. Describe relevant elements and how to set and test them to get > > the expected DRM blend mode on DCN hw. > > > > Signed-off-by: Melissa Wen > > --- > > .../gpu/amdgpu/display/display-manager.rst| 98 +++ > > Documentation/gpu/drm-kms.rst | 2 + > > 2 files changed, 100 insertions(+) > > > > diff --git a/Documentation/gpu/amdgpu/display/display-manager.rst > > b/Documentation/gpu/amdgpu/display/display-manager.rst > > index 8960a5f1fa66..7a495ed1f69e 100644 > > --- a/Documentation/gpu/amdgpu/display/display-manager.rst > > +++ b/Documentation/gpu/amdgpu/display/display-manager.rst > > @@ -84,3 +84,101 @@ families below. > > **DCN 3.0 family color caps and mapping** > > .. kernel-figure:: dcn3_cm_drm_current.svg > > + > > +Blend Mode Properties > > += > > + > > +Pixel blend mode is a DRM plane composition property of > > :c:type:`drm_plane` used to > > +describes how pixels from a foreground plane (fg) are composited with the > > +background plane (bg). Here, we present main concepts of DRM blend mode to > > help > > +to understand how this property is mapped to AMD DC interface. See more > > about > > +this DRM property and the alpha blending equations in :ref:`DRM Plane > > +Composition Properties `. > > + > > +Basically, a blend mode sets the alpha blending equation for plane > > +composition that fits the mode in which the alpha channel affects the > > state of > > +pixel color values and, therefore, the resulted pixel color. For > > +example, consider the following elements of the alpha blending equation: > > + > > +- *fg.rgb*: Each of the RGB component values from the foreground's pixel. > > +- *fg.alpha*: Alpha component value from the foreground's pixel. > > +- *bg.rgb*: Each of the RGB component values from the background. > > +- *plane_alpha*: Plane alpha value set by the **plane "alpha" property**, > > see > > + more in `DRM Plane Composition Properties > > `. > > You forgot to use :ref: in here. > > > + > > +in the basic alpha blending equation:: > > + > > + out.rgb = alpha * fg.rgb + (1 - alpha) * bg.rgb > > + > > +the alpha channel value of each pixel in a plane is ignored and only the > > plane > > +alpha affects the resulted pixel color values. > > + > > +DRM has three blend mode to define the blend formula in the plane > > composition: > > + > > +* **None**: Blend formula that ignores the pixel alpha. > > + > > +* **Pre-multiplied**: Blend formula that assumes the pixel color values in > > a > > + plane was already pre-multiplied by its own alpha channel before storage. > > + > > +* **Coverage**: Blend formula that assumes the pixel color values were not > > + pre-multiplied with the alpha channel values. > > + > > +and pre-multiplied is the default pixel blend mode, that means, when no > > blend > > +mode property is created or defined, DRM considers the plane's pixels has > > +pre-multiplied color values. On IGT GPU tools, the kms_plane_alpha_blend > > test > > +provides a set of subtests to verify plane alpha and blend mode properties. > > + > > +The DRM blend mode and its elements are then mapped by AMDGPU display > > manager > > +(DM) to program the blending configuration of the Multiple Pipe/Plane > > Combined > > +(MPC), as follows: > > + > > +.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h > > + :doc: mpc-overview > > + > > +.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h > > + :functions: mpcc_blnd_cfg > > + > > +Therefore, the blending configuration for a single MPCC instance on the MPC > > +tree is defined by :c:type:`mpcc_blnd_cfg`, where > > +:c:type:`pre_multiplied_alpha` is the alpha pre-multiplied mode flag used > > to > > +set :c:type:`MPCC_ALPHA_MULTIPLIED_MODE`. It controls whether alpha is > > +multiplied (true/false), being only true for DRM pre-multiplied blend mode. > > +:c:type:`mpcc_alpha_blend_mode` defines the alpha blend mode regarding > > pixel > > +alpha and plane alpha values. It sets one of the three modes for > > +:c:type:`MPCC_ALPHA_BLND_MODE`, as described below. > > + > > +.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h > > + :functions: mpcc_alpha_blend_mode > > + > > +DM then maps the elements of `enum mpcc_alpha_blend_mode` to those in the > > DRM > > +blend formula, as follows: > > + > > +* *MPC pixel alpha* matches *DRM fg.alpha* as the alpha component value > > + from the plane's pixel > > +* *MPC global alpha* matches *DRM plane_alpha* when the pixel alpha should > > + be ignored and, therefore, pixel values are not pre-multiplied > > +* *MPC global gain* assumes *MPC global alpha* value when both *DRM > > + fg.alpha* and *DRM plane_alpha* participate in the blend equation > > +
Re: [PATCH 4/4] Documentation/gpu/amdgpu/amdgpu_dm: add DM docs for pixel blend mode
On 16/07/2022 19:25, Melissa Wen wrote: AMD GPU display manager (DM) maps DRM pixel blend modes (None, Pre-multiplied, Coverage) to MPC hw blocks through blend configuration options. Describe relevant elements and how to set and test them to get the expected DRM blend mode on DCN hw. Signed-off-by: Melissa Wen --- .../gpu/amdgpu/display/display-manager.rst| 98 +++ Documentation/gpu/drm-kms.rst | 2 + 2 files changed, 100 insertions(+) diff --git a/Documentation/gpu/amdgpu/display/display-manager.rst b/Documentation/gpu/amdgpu/display/display-manager.rst index 8960a5f1fa66..7a495ed1f69e 100644 --- a/Documentation/gpu/amdgpu/display/display-manager.rst +++ b/Documentation/gpu/amdgpu/display/display-manager.rst @@ -84,3 +84,101 @@ families below. **DCN 3.0 family color caps and mapping** .. kernel-figure:: dcn3_cm_drm_current.svg + +Blend Mode Properties += + +Pixel blend mode is a DRM plane composition property of :c:type:`drm_plane` used to +describes how pixels from a foreground plane (fg) are composited with the +background plane (bg). Here, we present main concepts of DRM blend mode to help +to understand how this property is mapped to AMD DC interface. See more about +this DRM property and the alpha blending equations in :ref:`DRM Plane +Composition Properties `. + +Basically, a blend mode sets the alpha blending equation for plane +composition that fits the mode in which the alpha channel affects the state of +pixel color values and, therefore, the resulted pixel color. For +example, consider the following elements of the alpha blending equation: + +- *fg.rgb*: Each of the RGB component values from the foreground's pixel. +- *fg.alpha*: Alpha component value from the foreground's pixel. +- *bg.rgb*: Each of the RGB component values from the background. +- *plane_alpha*: Plane alpha value set by the **plane "alpha" property**, see + more in `DRM Plane Composition Properties `. You forgot to use :ref: in here. + +in the basic alpha blending equation:: + + out.rgb = alpha * fg.rgb + (1 - alpha) * bg.rgb + +the alpha channel value of each pixel in a plane is ignored and only the plane +alpha affects the resulted pixel color values. + +DRM has three blend mode to define the blend formula in the plane composition: + +* **None**: Blend formula that ignores the pixel alpha. + +* **Pre-multiplied**: Blend formula that assumes the pixel color values in a + plane was already pre-multiplied by its own alpha channel before storage. + +* **Coverage**: Blend formula that assumes the pixel color values were not + pre-multiplied with the alpha channel values. + +and pre-multiplied is the default pixel blend mode, that means, when no blend +mode property is created or defined, DRM considers the plane's pixels has +pre-multiplied color values. On IGT GPU tools, the kms_plane_alpha_blend test +provides a set of subtests to verify plane alpha and blend mode properties. + +The DRM blend mode and its elements are then mapped by AMDGPU display manager +(DM) to program the blending configuration of the Multiple Pipe/Plane Combined +(MPC), as follows: + +.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h + :doc: mpc-overview + +.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h + :functions: mpcc_blnd_cfg + +Therefore, the blending configuration for a single MPCC instance on the MPC +tree is defined by :c:type:`mpcc_blnd_cfg`, where +:c:type:`pre_multiplied_alpha` is the alpha pre-multiplied mode flag used to +set :c:type:`MPCC_ALPHA_MULTIPLIED_MODE`. It controls whether alpha is +multiplied (true/false), being only true for DRM pre-multiplied blend mode. +:c:type:`mpcc_alpha_blend_mode` defines the alpha blend mode regarding pixel +alpha and plane alpha values. It sets one of the three modes for +:c:type:`MPCC_ALPHA_BLND_MODE`, as described below. + +.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h + :functions: mpcc_alpha_blend_mode + +DM then maps the elements of `enum mpcc_alpha_blend_mode` to those in the DRM +blend formula, as follows: + +* *MPC pixel alpha* matches *DRM fg.alpha* as the alpha component value + from the plane's pixel +* *MPC global alpha* matches *DRM plane_alpha* when the pixel alpha should + be ignored and, therefore, pixel values are not pre-multiplied +* *MPC global gain* assumes *MPC global alpha* value when both *DRM + fg.alpha* and *DRM plane_alpha* participate in the blend equation + +In short, *fg.alpha* is ignored by selecting +:c:type:`MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA`. On the other hand, (plane_alpha * +fg.alpha) component becomes available by selecting +:c:type:`MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA_COMBINED_GLOBAL_GAIN`. And the +:c:type:`MPCC_ALPHA_MULTIPLIED_MODE` defines if the pixel color values are +pre-multiplied by alpha or not. + +Blend configuration flow + + +The alpha blending equation is configured from DRM to DC interface by the
