From 106b4a2a78b2a2f14885604891957b84bba502db Mon Sep 17 00:00:00 2001 From: Adrian Betschart Date: Fri, 11 Sep 2026 17:13:14 +0200 Subject: drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validation 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 Assisted-by: Claude Code:claude-fable-5-1 Signed-off-by: Adrian Betschart Reviewed-by: Fangzhi Zuo Tested-by: Adolfo Rodrigues Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7) --- rust/syn/thread.rs | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 rust/syn/thread.rs (limited to 'rust/syn/thread.rs') diff --git a/rust/syn/thread.rs b/rust/syn/thread.rs new file mode 100644 index 000000000..4165a173d --- /dev/null +++ b/rust/syn/thread.rs @@ -0,0 +1,62 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +use std::fmt::{self, Debug}; +use std::thread::{self, ThreadId}; + +/// ThreadBound is a Sync-maker and Send-maker that allows accessing a value +/// of type T only from the original thread on which the ThreadBound was +/// constructed. +pub(crate) struct ThreadBound { + value: T, + thread_id: ThreadId, +} + +unsafe impl Sync for ThreadBound {} + +// Send bound requires Copy, as otherwise Drop could run in the wrong place. +// +// Today Copy and Drop are mutually exclusive so `T: Copy` implies `T: !Drop`. +// This impl needs to be revisited if that restriction is relaxed in the future. +unsafe impl Send for ThreadBound {} + +impl ThreadBound { + pub(crate) fn new(value: T) -> Self { + ThreadBound { + value, + thread_id: thread::current().id(), + } + } + + pub(crate) fn get(&self) -> Option<&T> { + if thread::current().id() == self.thread_id { + Some(&self.value) + } else { + None + } + } +} + +impl Debug for ThreadBound { + fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { + match self.get() { + Some(value) => Debug::fmt(value, formatter), + None => formatter.write_str("unknown"), + } + } +} + +// Copy the bytes of T, even if the currently running thread is the "wrong" +// thread. This is fine as long as the original thread is not simultaneously +// mutating this value via interior mutability, which would be a data race. +// +// Currently `T: Copy` is sufficient to guarantee that T contains no interior +// mutability, because _all_ interior mutability in Rust is built on +// std::cell::UnsafeCell, which has no Copy impl. This impl needs to be +// revisited if that restriction is relaxed in the future. +impl Copy for ThreadBound {} + +impl Clone for ThreadBound { + fn clone(&self) -> Self { + *self + } +} -- cgit v1.3.1