1====================== 2AMDgpu Display Manager 3====================== 4 5.. contents:: Table of Contents 6 :depth: 3 7 8.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 9 :doc: overview 10 11.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h 12 :internal: 13 14Lifecycle 15========= 16 17.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 18 :doc: DM Lifecycle 19 20.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 21 :functions: dm_hw_init dm_hw_fini 22 23Interrupts 24========== 25 26.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c 27 :doc: overview 28 29.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c 30 :internal: 31 32.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 33 :functions: register_hpd_handlers dm_crtc_high_irq dm_pflip_high_irq 34 35Atomic Implementation 36===================== 37 38.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 39 :doc: atomic 40 41.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 42 :functions: amdgpu_dm_atomic_check amdgpu_dm_atomic_commit_tail 43 44Color Management Properties 45=========================== 46 47.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c 48 :doc: overview 49 50.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c 51 :internal: 52 53 54DC Color Capabilities between DCN generations 55--------------------------------------------- 56 57DRM/KMS framework defines three CRTC color correction properties: degamma, 58color transformation matrix (CTM) and gamma, and two properties for degamma and 59gamma LUT sizes. AMD DC programs some of the color correction features 60pre-blending but DRM/KMS has not per-plane color correction properties. 61 62In general, the DRM CRTC color properties are programmed to DC, as follows: 63CRTC gamma after blending, and CRTC degamma pre-blending. Although CTM is 64programmed after blending, it is mapped to DPP hw blocks (pre-blending). Other 65color caps available in the hw is not currently exposed by DRM interface and 66are bypassed. 67 68.. kernel-doc:: drivers/gpu/drm/amd/display/dc/dc.h 69 :doc: color-management-caps 70 71.. kernel-doc:: drivers/gpu/drm/amd/display/dc/dc.h 72 :internal: 73 74The color pipeline has undergone major changes between DCN hardware 75generations. What's possible to do before and after blending depends on 76hardware capabilities, as illustrated below by the DCN 2.0 and DCN 3.0 families 77schemas. 78 79**DCN 2.0 family color caps and mapping** 80 81.. kernel-figure:: dcn2_cm_drm_current.svg 82 83**DCN 3.0 family color caps and mapping** 84 85.. kernel-figure:: dcn3_cm_drm_current.svg 86 87Blend Mode Properties 88===================== 89 90Pixel blend mode is a DRM plane composition property of :c:type:`drm_plane` used to 91describes how pixels from a foreground plane (fg) are composited with the 92background plane (bg). Here, we present main concepts of DRM blend mode to help 93to understand how this property is mapped to AMD DC interface. See more about 94this DRM property and the alpha blending equations in :ref:`DRM Plane 95Composition Properties <plane_composition_properties>`. 96 97Basically, a blend mode sets the alpha blending equation for plane 98composition that fits the mode in which the alpha channel affects the state of 99pixel color values and, therefore, the resulted pixel color. For 100example, consider the following elements of the alpha blending equation: 101 102- *fg.rgb*: Each of the RGB component values from the foreground's pixel. 103- *fg.alpha*: Alpha component value from the foreground's pixel. 104- *bg.rgb*: Each of the RGB component values from the background. 105- *plane_alpha*: Plane alpha value set by the **plane "alpha" property**, see 106 more in :ref:`DRM Plane Composition Properties <plane_composition_properties>`. 107 108in the basic alpha blending equation:: 109 110 out.rgb = alpha * fg.rgb + (1 - alpha) * bg.rgb 111 112the alpha channel value of each pixel in a plane is ignored and only the plane 113alpha affects the resulted pixel color values. 114 115DRM has three blend mode to define the blend formula in the plane composition: 116 117* **None**: Blend formula that ignores the pixel alpha. 118 119* **Pre-multiplied**: Blend formula that assumes the pixel color values in a 120 plane was already pre-multiplied by its own alpha channel before storage. 121 122* **Coverage**: Blend formula that assumes the pixel color values were not 123 pre-multiplied with the alpha channel values. 124 125and pre-multiplied is the default pixel blend mode, that means, when no blend 126mode property is created or defined, DRM considers the plane's pixels has 127pre-multiplied color values. On IGT GPU tools, the kms_plane_alpha_blend test 128provides a set of subtests to verify plane alpha and blend mode properties. 129 130The DRM blend mode and its elements are then mapped by AMDGPU display manager 131(DM) to program the blending configuration of the Multiple Pipe/Plane Combined 132(MPC), as follows: 133 134.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h 135 :doc: mpc-overview 136 137.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h 138 :functions: mpcc_blnd_cfg 139 140Therefore, the blending configuration for a single MPCC instance on the MPC 141tree is defined by :c:type:`mpcc_blnd_cfg`, where 142:c:type:`pre_multiplied_alpha` is the alpha pre-multiplied mode flag used to 143set :c:type:`MPCC_ALPHA_MULTIPLIED_MODE`. It controls whether alpha is 144multiplied (true/false), being only true for DRM pre-multiplied blend mode. 145:c:type:`mpcc_alpha_blend_mode` defines the alpha blend mode regarding pixel 146alpha and plane alpha values. It sets one of the three modes for 147:c:type:`MPCC_ALPHA_BLND_MODE`, as described below. 148 149.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h 150 :functions: mpcc_alpha_blend_mode 151 152DM then maps the elements of `enum mpcc_alpha_blend_mode` to those in the DRM 153blend formula, as follows: 154 155* *MPC pixel alpha* matches *DRM fg.alpha* as the alpha component value 156 from the plane's pixel 157* *MPC global alpha* matches *DRM plane_alpha* when the pixel alpha should 158 be ignored and, therefore, pixel values are not pre-multiplied 159* *MPC global gain* assumes *MPC global alpha* value when both *DRM 160 fg.alpha* and *DRM plane_alpha* participate in the blend equation 161 162In short, *fg.alpha* is ignored by selecting 163:c:type:`MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA`. On the other hand, (plane_alpha * 164fg.alpha) component becomes available by selecting 165:c:type:`MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA_COMBINED_GLOBAL_GAIN`. And the 166:c:type:`MPCC_ALPHA_MULTIPLIED_MODE` defines if the pixel color values are 167pre-multiplied by alpha or not. 168 169Blend configuration flow 170------------------------ 171 172The alpha blending equation is configured from DRM to DC interface by the 173following path: 174 1751. When updating a :c:type:`drm_plane_state <drm_plane_state>`, DM calls 176 :c:type:`fill_blending_from_plane_state()` that maps 177 :c:type:`drm_plane_state <drm_plane_state>` attributes to 178 :c:type:`dc_plane_info <dc_plane_info>` struct to be handled in the 179 OS-agnostic component (DC). 180 1812. On DC interface, :c:type:`struct mpcc_blnd_cfg <mpcc_blnd_cfg>` programs the 182 MPCC blend configuration considering the :c:type:`dc_plane_info 183 <dc_plane_info>` input from DPP. 184
