linux-kernel - [PATCH AUTOSEL 6.6 06/11] drm/amd/display: fix link_set_dpms

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Message-Id: <20250519212237.1986368-6-sashal@kernel.org>
Date: Mon, 19 May 2025 17:22:32 -0400
From: Sasha Levin <sashal@...nel.org>
To: patches@...ts.linux.dev,
	stable@...r.kernel.org
Cc: George Shen <george.shen@....com>,
	Wenjing Liu <wenjing.liu@....com>,
	Ray Wu <ray.wu@....com>,
	Daniel Wheeler <daniel.wheeler@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	harry.wentland@....com,
	sunpeng.li@....com,
	christian.koenig@....com,
	David1.Zhou@....com,
	airlied@...ux.ie,
	daniel@...ll.ch,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 06/11] drm/amd/display: fix link_set_dpms_off multi-display MST corner case

From: George Shen <george.shen@....com>

[ Upstream commit 3c1a467372e0c356b1d3c59f6d199ed5a6612dd1 ]

[Why & How]
When MST config is unplugged/replugged too quickly, it can potentially
result in a scenario where previous DC state has not been reset before
the HPD link detection sequence begins. In this case, driver will
disable the streams/link prior to re-enabling the link for link
training.

There is a bug in the current logic that does not account for the fact
that current_state can be released and cleared prior to swapping to a
new state (resulting in the pipe_ctx stream pointers to be cleared) in
between disabling streams.

To resolve this, cache the original streams prior to committing any
stream updates.

Reviewed-by: Wenjing Liu <wenjing.liu@....com>
Signed-off-by: George Shen <george.shen@....com>
Signed-off-by: Ray Wu <ray.wu@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
(cherry picked from commit 1561782686ccc36af844d55d31b44c938dd412dc)
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/link/link_dpms.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c
index 4901e27f678bc..9b470812d96a5 100644
--- a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c
+++ b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c
@@ -145,6 +145,7 @@ void link_blank_dp_stream(struct dc_link *link, bool hw_init)
 void link_set_all_streams_dpms_off_for_link(struct dc_link *link)
 {
 	struct pipe_ctx *pipes[MAX_PIPES];
+	struct dc_stream_state *streams[MAX_PIPES];
 	struct dc_state *state = link->dc->current_state;
 	uint8_t count;
 	int i;
@@ -157,10 +158,18 @@ void link_set_all_streams_dpms_off_for_link(struct dc_link *link)
 
 	link_get_master_pipes_with_dpms_on(link, state, &count, pipes);
 
+	/* The subsequent call to dc_commit_updates_for_stream for a full update
+	 * will release the current state and swap to a new state. Releasing the
+	 * current state results in the stream pointers in the pipe_ctx structs
+	 * to be zero'd. Hence, cache all streams prior to dc_commit_updates_for_stream.
+	 */
+	for (i = 0; i < count; i++)
+		streams[i] = pipes[i]->stream;
+
 	for (i = 0; i < count; i++) {
-		stream_update.stream = pipes[i]->stream;
+		stream_update.stream = streams[i];
 		dc_commit_updates_for_stream(link->ctx->dc, NULL, 0,
-				pipes[i]->stream, &stream_update,
+				streams[i], &stream_update,
 				state);
 	}
 
-- 
2.39.5