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, 22 insertions, 0 deletions

diff --git a/include/net/aligned_data.h b/include/net/aligned_data.h
new file mode 100644
index 000000000..e1a1c8aed
--- /dev/null
+++ b/include/net/aligned_data.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _NET_ALIGNED_DATA_H
+#define _NET_ALIGNED_DATA_H
+
+#include <linux/atomic.h>
+#include <linux/types.h>
+
+/* Structure holding cacheline aligned fields on SMP builds.
+ * Each field or group should have an ____cacheline_aligned_in_smp
+ * attribute to ensure no accidental false sharing can happen.
+ */
+struct net_aligned_data {
+	atomic64_t	net_cookie ____cacheline_aligned_in_smp;
+#if defined(CONFIG_INET)
+	atomic_long_t tcp_memory_allocated ____cacheline_aligned_in_smp;
+	atomic_long_t udp_memory_allocated ____cacheline_aligned_in_smp;
+#endif
+};
+
+extern struct net_aligned_data net_aligned_data;
+
+#endif /* _NET_ALIGNED_DATA_H */