184 lines
7.0 KiB
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184 lines
7.0 KiB
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======================
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AMDgpu Display Manager
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======================
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.. contents:: Table of Contents
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:depth: 3
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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:doc: overview
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
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:internal:
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Lifecycle
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=========
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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:doc: DM Lifecycle
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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:functions: dm_hw_init dm_hw_fini
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Interrupts
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==========
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
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:doc: overview
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
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:internal:
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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:functions: register_hpd_handlers dm_crtc_high_irq dm_pflip_high_irq
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Atomic Implementation
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=====================
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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:doc: atomic
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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:functions: amdgpu_dm_atomic_check amdgpu_dm_atomic_commit_tail
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Color Management Properties
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===========================
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
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:doc: overview
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.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
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:internal:
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DC Color Capabilities between DCN generations
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---------------------------------------------
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DRM/KMS framework defines three CRTC color correction properties: degamma,
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color transformation matrix (CTM) and gamma, and two properties for degamma and
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gamma LUT sizes. AMD DC programs some of the color correction features
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pre-blending but DRM/KMS has not per-plane color correction properties.
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In general, the DRM CRTC color properties are programmed to DC, as follows:
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CRTC gamma after blending, and CRTC degamma pre-blending. Although CTM is
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programmed after blending, it is mapped to DPP hw blocks (pre-blending). Other
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color caps available in the hw is not currently exposed by DRM interface and
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are bypassed.
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.. kernel-doc:: drivers/gpu/drm/amd/display/dc/dc.h
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:doc: color-management-caps
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.. kernel-doc:: drivers/gpu/drm/amd/display/dc/dc.h
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:internal:
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The color pipeline has undergone major changes between DCN hardware
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generations. What's possible to do before and after blending depends on
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hardware capabilities, as illustrated below by the DCN 2.0 and DCN 3.0 families
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schemas.
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**DCN 2.0 family color caps and mapping**
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.. kernel-figure:: dcn2_cm_drm_current.svg
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**DCN 3.0 family color caps and mapping**
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.. kernel-figure:: dcn3_cm_drm_current.svg
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Blend Mode Properties
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=====================
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Pixel blend mode is a DRM plane composition property of :c:type:`drm_plane` used to
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describes how pixels from a foreground plane (fg) are composited with the
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background plane (bg). Here, we present main concepts of DRM blend mode to help
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to understand how this property is mapped to AMD DC interface. See more about
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this DRM property and the alpha blending equations in :ref:`DRM Plane
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Composition Properties <plane_composition_properties>`.
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Basically, a blend mode sets the alpha blending equation for plane
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composition that fits the mode in which the alpha channel affects the state of
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pixel color values and, therefore, the resulted pixel color. For
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example, consider the following elements of the alpha blending equation:
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- *fg.rgb*: Each of the RGB component values from the foreground's pixel.
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- *fg.alpha*: Alpha component value from the foreground's pixel.
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- *bg.rgb*: Each of the RGB component values from the background.
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- *plane_alpha*: Plane alpha value set by the **plane "alpha" property**, see
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more in :ref:`DRM Plane Composition Properties <plane_composition_properties>`.
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in the basic alpha blending equation::
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out.rgb = alpha * fg.rgb + (1 - alpha) * bg.rgb
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the alpha channel value of each pixel in a plane is ignored and only the plane
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alpha affects the resulted pixel color values.
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DRM has three blend mode to define the blend formula in the plane composition:
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* **None**: Blend formula that ignores the pixel alpha.
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* **Pre-multiplied**: Blend formula that assumes the pixel color values in a
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plane was already pre-multiplied by its own alpha channel before storage.
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* **Coverage**: Blend formula that assumes the pixel color values were not
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pre-multiplied with the alpha channel values.
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and pre-multiplied is the default pixel blend mode, that means, when no blend
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mode property is created or defined, DRM considers the plane's pixels has
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pre-multiplied color values. On IGT GPU tools, the kms_plane_alpha_blend test
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provides a set of subtests to verify plane alpha and blend mode properties.
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The DRM blend mode and its elements are then mapped by AMDGPU display manager
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(DM) to program the blending configuration of the Multiple Pipe/Plane Combined
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(MPC), as follows:
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.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h
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:doc: mpc-overview
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.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h
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:functions: mpcc_blnd_cfg
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Therefore, the blending configuration for a single MPCC instance on the MPC
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tree is defined by :c:type:`mpcc_blnd_cfg`, where
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:c:type:`pre_multiplied_alpha` is the alpha pre-multiplied mode flag used to
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set :c:type:`MPCC_ALPHA_MULTIPLIED_MODE`. It controls whether alpha is
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multiplied (true/false), being only true for DRM pre-multiplied blend mode.
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:c:type:`mpcc_alpha_blend_mode` defines the alpha blend mode regarding pixel
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alpha and plane alpha values. It sets one of the three modes for
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:c:type:`MPCC_ALPHA_BLND_MODE`, as described below.
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.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h
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:functions: mpcc_alpha_blend_mode
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DM then maps the elements of `enum mpcc_alpha_blend_mode` to those in the DRM
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blend formula, as follows:
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* *MPC pixel alpha* matches *DRM fg.alpha* as the alpha component value
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from the plane's pixel
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* *MPC global alpha* matches *DRM plane_alpha* when the pixel alpha should
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be ignored and, therefore, pixel values are not pre-multiplied
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* *MPC global gain* assumes *MPC global alpha* value when both *DRM
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fg.alpha* and *DRM plane_alpha* participate in the blend equation
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In short, *fg.alpha* is ignored by selecting
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:c:type:`MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA`. On the other hand, (plane_alpha *
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fg.alpha) component becomes available by selecting
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:c:type:`MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA_COMBINED_GLOBAL_GAIN`. And the
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:c:type:`MPCC_ALPHA_MULTIPLIED_MODE` defines if the pixel color values are
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pre-multiplied by alpha or not.
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Blend configuration flow
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------------------------
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The alpha blending equation is configured from DRM to DC interface by the
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following path:
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1. When updating a :c:type:`drm_plane_state <drm_plane_state>`, DM calls
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:c:type:`fill_blending_from_plane_state()` that maps
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:c:type:`drm_plane_state <drm_plane_state>` attributes to
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:c:type:`dc_plane_info <dc_plane_info>` struct to be handled in the
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OS-agnostic component (DC).
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2. On DC interface, :c:type:`struct mpcc_blnd_cfg <mpcc_blnd_cfg>` programs the
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MPCC blend configuration considering the :c:type:`dc_plane_info
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<dc_plane_info>` input from DPP.
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