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, 123 insertions, 0 deletions

diff --git a/Documentation/sphinx/parser_yaml.py b/Documentation/sphinx/parser_yaml.py
new file mode 100755
index 000000000..634d84a20
--- /dev/null
+++ b/Documentation/sphinx/parser_yaml.py
@@ -0,0 +1,123 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright 2025 Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
+
+"""
+Sphinx extension for processing YAML files
+"""
+
+import os
+import re
+import sys
+
+from pprint import pformat
+
+from docutils import statemachine
+from docutils.parsers.rst import Parser as RSTParser
+from docutils.parsers.rst import states
+from docutils.statemachine import ViewList
+
+from sphinx.util import logging
+from sphinx.parsers import Parser
+
+srctree = os.path.abspath(os.environ["srctree"])
+sys.path.insert(0, os.path.join(srctree, "tools/net/ynl/pyynl/lib"))
+
+from doc_generator import YnlDocGenerator        # pylint: disable=C0413
+
+logger = logging.getLogger(__name__)
+
+class YamlParser(Parser):
+    """
+    Kernel parser for YAML files.
+
+    This is a simple sphinx.Parser to handle yaml files inside the
+    Kernel tree that will be part of the built documentation.
+
+    The actual parser function is not contained here: the code was
+    written in a way that parsing yaml for different subsystems
+    can be done from a single dispatcher.
+
+    All it takes to have parse YAML patches is to have an import line:
+
+            from some_parser_code import NewYamlGenerator
+
+    To this module. Then add an instance of the parser with:
+
+            new_parser = NewYamlGenerator()
+
+    and add a logic inside parse() to handle it based on the path,
+    like this:
+
+            if "/foo" in fname:
+                msg = self.new_parser.parse_yaml_file(fname)
+    """
+
+    supported = ('yaml', )
+
+    netlink_parser = YnlDocGenerator()
+
+    re_lineno = re.compile(r"\.\. LINENO ([0-9]+)$")
+
+    tab_width = 8
+
+    def rst_parse(self, inputstring, document, msg):
+        """
+        Receives a ReST content that was previously converted by the
+        YAML parser, adding it to the document tree.
+        """
+
+        self.setup_parse(inputstring, document)
+
+        result = ViewList()
+
+        self.statemachine = states.RSTStateMachine(state_classes=states.state_classes,
+                                                   initial_state='Body',
+                                                   debug=document.reporter.debug_flag)
+
+        try:
+            # Parse message with RSTParser
+            lineoffset = 0;
+
+            lines = statemachine.string2lines(msg, self.tab_width,
+                                              convert_whitespace=True)
+
+            for line in lines:
+                match = self.re_lineno.match(line)
+                if match:
+                    lineoffset = int(match.group(1))
+                    continue
+
+                result.append(line, document.current_source, lineoffset)
+
+            self.statemachine.run(result, document)
+
+        except Exception as e:
+            document.reporter.error("YAML parsing error: %s" % pformat(e))
+
+        self.finish_parse()
+
+    # Overrides docutils.parsers.Parser. See sphinx.parsers.RSTParser
+    def parse(self, inputstring, document):
+        """Check if a YAML is meant to be parsed."""
+
+        fname = document.current_source
+
+        # Handle netlink yaml specs
+        if "/netlink/specs/" in fname:
+            msg = self.netlink_parser.parse_yaml_file(fname)
+            self.rst_parse(inputstring, document, msg)
+
+        # All other yaml files are ignored
+
+def setup(app):
+    """Setup function for the Sphinx extension."""
+
+    # Add YAML parser
+    app.add_source_parser(YamlParser)
+    app.add_source_suffix('.yaml', 'yaml')
+
+    return {
+        'version': '1.0',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }