drm/amd/display: Default HDMI RGB output to limited range on CTA modes

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With the Broadcast RGB property at Automatic,
amdgpu_dm_get_output_color_space() selects COLOR_SPACE_SRGB for RGB
output, so DC neither compresses the pixels nor, without a QS-capable
sink, signals full range in the AVI InfoFrame. A sink that follows
CTA-861 treats the default quantization of a CTA video format as limited
and expands 16-235 to 0-255: everything below 16 is crushed to black,
everything above 235 clips.

Follow the CTA-861 default for Automatic instead, as the DRM HDMI state
helper (hdmi_is_limited_range()) and i915 do: limited range on an HDMI
sink for CTA modes other than 640x480, full range elsewhere. Full and
Limited keep their explicit meaning. The same rule applies to the
BT.2020 RGB branch. With commit 892659399f ("drm/amd/display:
Propagate HDMI RGB quantization selectability") the AVI InfoFrame then
carries the matching Q value on sinks that support selection.

Measured on a Radeon RX 7600 (DCN 3.2.1) driving a JVC DLA-RS4100 at
1920x1080p24 RGB 12 bpc: the sink reports the signal as limited range
while the picture shows crushed shadows; rendering limited range in the
client makes it match a reference source.

The KUnit fixtures that reach amdgpu_dm_get_output_color_space() now
carry a connector, since Automatic reads its display_info, and five
cases cover the new rule.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/5796
Reviewed-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Adrian Betschart <adrian.betschart@cinemaone.ch>
Assisted-by: Claude Code:claude-fable-5-1
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit d23f735d0e)

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Adrian Betschart 2026-09-10 20:56:48 +02:00 • committed by Alex Deucher

parent 015e72cde5

commit eb5650d1f3

2 changed files with 137 additions and 2 deletions

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22

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c

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117

drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_connector_test.c

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