drm/amd/display: fix wrong color value mapping on MCM shaper LUT

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[ Upstream commit 8f959d37c1 ]

Some shimmer/colorful points appears when using the steamOS color
pipeline for HDR on gaming with DCN32. These points look like black
values being wrongly mapped to red/blue/green values. It was caused
because the number of hw points in regular LUTs and in a shaper LUT was
treated as the same.

DCN3+ regular LUTs have 257 bases and implicit deltas (i.e. HW
calculates them), but shaper LUT is a special case: it has 256 bases and
256 deltas, as in DCN1-2 regular LUTs, and outputs 14-bit values.

Fix that by setting by decreasing in 1 the number of HW points computed
in the LUT segmentation so that shaper LUT (i.e. fixpoint == true) keeps
the same DCN10 CM logic and regular LUTs go with `hw_points + 1`.

CC: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Fixes: 4d5fd3d08e ("drm/amd/display: PQ tail accuracy")
Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 5006505b19)
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Melissa Wen 2026-01-22 12:20:29 -03:00 • committed by Greg Kroah-Hartman

parent 5003e92af2

commit d4d5d152d9

1 changed files with 5 additions and 2 deletions

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drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c

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