[PATCH AUTOSEL 6.6 06/11] drm/amd/display: fix link_set_dpms_off multi-display MST corner case

Sasha Levin
2025-05-19T21:22:48Z

From: George Shen <george.shen@amd.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@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 1561782686ccc36af844d55d31b44c938dd412dc)
Signed-off-by: Sasha Levin <sashal@kernel.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