drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validationgrafted

amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and
uses the first encoding that validates. YCbCr 4:4:4 is listed before
RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the
"color format" property is left at AUTO, even though RGB fits the same
link.

That contradicts the documented AUTO behaviour for HDMI in enum
drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when
the bandwidth is not available or the mode is 4:2:0-only), which the
amdgpu implementation of the property also describes. It also leaves
the "Broadcast RGB" property without effect on such sinks, since the
quantization range it selects only applies to RGB output.

Try RGB first. The mask still holds every encoding the sink supports,
so a mode that cannot carry RGB falls back exactly as before.

For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced
through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI
sink that advertised it.

Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation")
Suggested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Assisted-by: Claude Code:claude-fable-5-1
Signed-off-by: Adrian Betschart <adrian.betschart@cinemaone.ch>
Reviewed-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7)

1 files changed, 28 insertions, 0 deletions

diff --git a/Documentation/Kconfig b/Documentation/Kconfig
new file mode 100644
index 000000000..8b6c4b84b
--- /dev/null
+++ b/Documentation/Kconfig
@@ -0,0 +1,28 @@
+if COMPILE_TEST
+
+menu "Documentation"
+
+config WARN_MISSING_DOCUMENTS
+	bool "Warn if there's a missing documentation file"
+	help
+	  It is not uncommon that a document gets renamed.
+	  This option makes the Kernel to check for missing dependencies,
+	  warning when something is missing. Works only if the Kernel
+	  is built from a git tree.
+
+	  If unsure, select 'N'.
+
+config WARN_ABI_ERRORS
+	bool "Warn if there are errors at ABI files"
+	help
+	  The files under Documentation/ABI should follow what's
+	  described at Documentation/ABI/README. Yet, as they're manually
+	  written, it would be possible that some of those files would
+	  have errors that would break them for being parsed by
+	  tools/docs/get_abi.py. Add a check to verify them.
+
+	  If unsure, select 'N'.
+
+endmenu
+
+endif