Documentation/amdgpu/display: add DC color caps info

Add details about color correction capabilities and explain a bit about
differences between DC hw generations and also how they are mapped
between DRM and DC interface. Two schemas for DCN 2.0 and 3.0 (converted
to svg from the original png) is included to illustrate it. They were
obtained from a discussion[1] in the amd-gfx mailing list.

[1] https://lore.kernel.org/amd-gfx/20220422142811.dm6vtk6v64jcwydk@mail.igalia.com/

v1:
- remove redundant comments (Harry)
- fix typos (Harry)

v2:
- reword introduction of color section
- add co-dev tag for Harry - who provided most of the info
- fix typos (Tales)
- describe missing struct parameters (Tales and Siqueira)

Co-developed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Tales Aparecida <tales.aparecida@gmail.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/Documentation/gpu/amdgpu/display/display-manager.rst b/Documentation/gpu/amdgpu/display/display-manager.rst
index b1b0f11aed83..88e2c08c7014 100644
--- a/Documentation/gpu/amdgpu/display/display-manager.rst
+++ b/Documentation/gpu/amdgpu/display/display-manager.rst
@@ -49,3 +49,37 @@ Color Management Properties
 
 .. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
    :internal:
+
+
+DC Color Capabilities between DCN generations
+---------------------------------------------
+
+DRM/KMS framework defines three CRTC color correction properties: degamma,
+color transformation matrix (CTM) and gamma, and two properties for degamma and
+gamma LUT sizes. AMD DC programs some of the color correction features
+pre-blending but DRM/KMS has not per-plane color correction properties.
+
+In general, the DRM CRTC color properties are programmed to DC, as follows:
+CRTC gamma after blending, and CRTC degamma pre-blending. Although CTM is
+programmed after blending, it is mapped to DPP hw blocks (pre-blending). Other
+color caps available in the hw is not currently exposed by DRM interface and
+are bypassed.
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/dc/dc.h
+   :doc: color-management-caps
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/dc/dc.h
+   :internal:
+
+The color pipeline has undergone major changes between DCN hardware
+generations. What's possible to do before and after blending depends on
+hardware capabilities, as illustrated below by the DCN 2.0 and DCN 3.0 families
+schemas.
+
+**DCN 2.0 family color caps and mapping**
+
+.. kernel-figure:: dcn2_cm_drm_current.svg
+
+**DCN 3.0 family color caps and mapping**
+
+.. kernel-figure:: dcn3_cm_drm_current.svg