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, 78 insertions, 0 deletions

diff --git a/Documentation/driver-api/wbrf.rst b/Documentation/driver-api/wbrf.rst
new file mode 100644
index 000000000..6b18833e2
--- /dev/null
+++ b/Documentation/driver-api/wbrf.rst
@@ -0,0 +1,78 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+=================================
+WBRF - Wifi Band RFI Mitigations
+=================================
+
+Due to electrical and mechanical constraints in certain platform designs
+there may be likely interference of relatively high-powered harmonics of
+the GPU memory clocks with local radio module frequency bands used by
+certain Wifi bands.
+
+To mitigate possible RFI interference producers can advertise the
+frequencies in use and consumers can use this information to avoid using
+these frequencies for sensitive features.
+
+When a platform is known to have this issue with any contained devices,
+the platform designer will advertise the availability of this feature via
+ACPI devices with a device specific method (_DSM).
+* Producers with this _DSM will be able to advertise the frequencies in use.
+* Consumers with this _DSM will be able to register for notifications of
+frequencies in use.
+
+Some general terms
+==================
+
+Producer: such component who can produce high-powered radio frequency
+Consumer: such component who can adjust its in-use frequency in
+response to the radio frequencies of other components to mitigate the
+possible RFI.
+
+To make the mechanism function, those producers should notify active use
+of their particular frequencies so that other consumers can make relative
+internal adjustments as necessary to avoid this resonance.
+
+ACPI interface
+==============
+
+Although initially used by for wifi + dGPU use cases, the ACPI interface
+can be scaled to any type of device that a platform designer discovers
+can cause interference.
+
+The GUID used for the _DSM is 7B7656CF-DC3D-4C1C-83E9-66E721DE3070.
+
+3 functions are available in this _DSM:
+
+* 0: discover # of functions available
+* 1: record RF bands in use
+* 2: retrieve RF bands in use
+
+Driver programming interface
+============================
+
+.. kernel-doc:: drivers/platform/x86/amd/wbrf.c
+
+Sample Usage
+=============
+
+The expected flow for the producers:
+1. During probe, call `acpi_amd_wbrf_supported_producer` to check if WBRF
+can be enabled for the device.
+2. On using some frequency band, call `acpi_amd_wbrf_add_remove` with 'add'
+param to get other consumers properly notified.
+3. Or on stopping using some frequency band, call
+`acpi_amd_wbrf_add_remove` with 'remove' param to get other consumers notified.
+
+The expected flow for the consumers:
+1. During probe, call `acpi_amd_wbrf_supported_consumer` to check if WBRF
+can be enabled for the device.
+2. Call `amd_wbrf_register_notifier` to register for notification
+of frequency band change(add or remove) from other producers.
+3. Call the `amd_wbrf_retrieve_freq_band` initially to retrieve
+current active frequency bands considering some producers may broadcast
+such information before the consumer is up.
+4. On receiving a notification for frequency band change, run
+`amd_wbrf_retrieve_freq_band` again to retrieve the latest
+active frequency bands.
+5. During driver cleanup, call `amd_wbrf_unregister_notifier` to
+unregister the notifier.