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drm/amd/display: Add AMD color pipeline doc

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Add kernel doc for AMD color pipeline.

Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patch.msgid.link/20251115000237.3561250-48-alex.hung@amd.com
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Harry Wentland 2025-11-14 17:02:12 -07:00 committed by Simon Ser
parent 0de2b1afea
commit d1aa2a2696
1 changed files with 102 additions and 20 deletions
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122
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
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@ -33,6 +33,32 @@
/**
* DOC: overview
*
* We have three types of color management in the AMD display driver.
* 1. the legacy &drm_crtc DEGAMMA, CTM, and GAMMA properties
* 2. AMD driver private color management on &drm_plane and &drm_crtc
* 3. AMD plane color pipeline
*
* The CRTC properties are the original color management. When they were
* implemented per-plane color management was not a thing yet. Because
* of that we could get away with plumbing the DEGAMMA and CTM
* properties to pre-blending HW functions. This is incompatible with
* per-plane color management, such as via the AMD private properties or
* the new drm_plane color pipeline. The only compatible CRTC property
* with per-plane color management is the GAMMA property as it is
* applied post-blending.
*
* The AMD driver private color management properties are only exposed
* when the kernel is built explicitly with -DAMD_PRIVATE_COLOR. They
* are temporary building blocks on the path to full-fledged &drm_plane
* and &drm_crtc color pipelines and lay the driver's groundwork for the
* color pipelines.
*
* The AMD plane color pipeline describes AMD's &drm_colorops via the
* &drm_plane's COLOR_PIPELINE property.
*
* drm_crtc Properties
* -------------------
*
* The DC interface to HW gives us the following color management blocks
* per pipe (surface):
*
@ -43,33 +69,89 @@
* - Surface regamma LUT (normalized)
* - Output CSC (normalized)
*
* But these aren't a direct mapping to DRM color properties. The current DRM
* interface exposes CRTC degamma, CRTC CTM and CRTC regamma while our hardware
* is essentially giving:
* But these aren't a direct mapping to DRM color properties. The
* current DRM interface exposes CRTC degamma, CRTC CTM and CRTC regamma
* while our hardware is essentially giving:
*
* Plane CTM -> Plane degamma -> Plane CTM -> Plane regamma -> Plane CTM
*
* The input gamma LUT block isn't really applicable here since it operates
* on the actual input data itself rather than the HW fp representation. The
* input and output CSC blocks are technically available to use as part of
* the DC interface but are typically used internally by DC for conversions
* between color spaces. These could be blended together with user
* adjustments in the future but for now these should remain untouched.
* The input gamma LUT block isn't really applicable here since it
* operates on the actual input data itself rather than the HW fp
* representation. The input and output CSC blocks are technically
* available to use as part of the DC interface but are typically used
* internally by DC for conversions between color spaces. These could be
* blended together with user adjustments in the future but for now
* these should remain untouched.
*
* The pipe blending also happens after these blocks so we don't actually
* support any CRTC props with correct blending with multiple planes - but we
* can still support CRTC color management properties in DM in most single
* plane cases correctly with clever management of the DC interface in DM.
* The pipe blending also happens after these blocks so we don't
* actually support any CRTC props with correct blending with multiple
* planes - but we can still support CRTC color management properties in
* DM in most single plane cases correctly with clever management of the
* DC interface in DM.
*
* As per DRM documentation, blocks should be in hardware bypass when their
* respective property is set to NULL. A linear DGM/RGM LUT should also
* considered as putting the respective block into bypass mode.
* As per DRM documentation, blocks should be in hardware bypass when
* their respective property is set to NULL. A linear DGM/RGM LUT should
* also considered as putting the respective block into bypass mode.
*
* This means that the following
* configuration is assumed to be the default:
* This means that the following configuration is assumed to be the
* default:
*
* Plane DGM Bypass -> Plane CTM Bypass -> Plane RGM Bypass -> ... CRTC
* DGM Bypass -> CRTC CTM Bypass -> CRTC RGM Bypass
*
* AMD Private Color Management on drm_plane
* -----------------------------------------
*
* The AMD private color management properties on a &drm_plane are:
*
* - AMD_PLANE_DEGAMMA_LUT
* - AMD_PLANE_DEGAMMA_LUT_SIZE
* - AMD_PLANE_DEGAMMA_TF
* - AMD_PLANE_HDR_MULT
* - AMD_PLANE_CTM
* - AMD_PLANE_SHAPER_LUT
* - AMD_PLANE_SHAPER_LUT_SIZE
* - AMD_PLANE_SHAPER_TF
* - AMD_PLANE_LUT3D
* - AMD_PLANE_LUT3D_SIZE
* - AMD_PLANE_BLEND_LUT
* - AMD_PLANE_BLEND_LUT_SIZE
* - AMD_PLANE_BLEND_TF
*
* The AMD private color management property on a &drm_crtc is:
*
* - AMD_CRTC_REGAMMA_TF
*
* Use of these properties is discouraged.
*
* AMD plane color pipeline
* ------------------------
*
* The AMD &drm_plane color pipeline is advertised for DCN generations
* 3.0 and newer. It exposes these elements in this order:
*
* 1. 1D curve colorop
* 2. Multiplier
* 3. 3x4 CTM
* 4. 1D curve colorop
* 5. 1D LUT
* 6. 3D LUT
* 7. 1D curve colorop
* 8. 1D LUT
*
* The multiplier (#2) is a simple multiplier that is applied to all
* channels.
*
* The 3x4 CTM (#3) is a simple 3x4 matrix.
*
* #1, and #7 are non-linear to linear curves. #4 is a linear to
* non-linear curve. They support sRGB, PQ, and BT.709/BT.2020 EOTFs or
* their inverse.
*
* The 1D LUTs (#5 and #8) are plain 4096 entry LUTs.
*
* The 3DLUT (#6) is a tetrahedrally interpolated 17 cube LUT.
*
* Plane DGM Bypass -> Plane CTM Bypass -> Plane RGM Bypass -> ...
* CRTC DGM Bypass -> CRTC CTM Bypass -> CRTC RGM Bypass
*/
#define MAX_DRM_LUT_VALUE 0xFFFF