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[Why] To prepare for the upcoming DRM plane color management properties we need to correct a lot of wrong behavior and assumptions made for CRTC color management. The documentation added by this commit in amdgpu_dm_color explains how the HW color pipeline works and its limitations with the DRM interface. The current implementation does the following wrong: - Implicit sRGB DGM when no CRTC DGM is set - Implicit sRGB RGM when no CRTC RGM is set - No way to specify a non-linear DGM matrix that produces correct output - No way to specify a correct RGM when a linear DGM is used We had workarounds for passing kms_color tests but not all of the behavior we had wrong was covered by these tests (especially when it comes to non-linear DGM). Testing both DGM and RGM at the same time isn't something kms_color tests well either. [How] The specifics for how color management works in AMDGPU and the new behavior can be found by reading the documentation added to amdgpu_dm_color.c from this patch. All of the incorrect cases from the old implementation have been addressed for the atomic interface, but there still a few TODOs for the legacy one. Note: this does cause regressions for kms_color@pipe-a-ctm-* over HDMI. The result looks correct from visual inspection but the CRC no longer matches. For reference, the test was previously doing the following: linear degamma -> CTM -> sRGB regamma -> RGB to YUV (709) -> ... Now the test is doing: linear degamma -> CTM -> linear regamma -> RGB to YUV (709) -> ... Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com> Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com> Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.