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drm/amd/display: dce100: skip non-DP stream encoders for DP MST

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On DCE8-class ASICs (e.g. Bonaire), the resource pool contains digital
DIG stream encoders plus one analog DAC encoder. When assigning a stream
encoder for a second DisplayPort MST stream, if the preferred digital
encoder is already acquired, dce100_find_first_free_match_stream_enc_for_link()
falls back to the first free pool entry. That entry may be the analog
encoder, whose funcs table lacks DP hooks such as dp_set_stream_attribute.
The subsequent atomic commit then dereferences NULL function pointers in
link_set_dpms_on() and crashes.

Skip encoders without dp_set_stream_attribute when the stream uses a DP
signal (including MST). Use dc_is_dp_signal(stream->signal) for the MST
fallback path instead of checking only the link connector signal.

Tested on:
- GPU: AMD Radeon R7 260X (Bonaire / DCE8)
- Board: Supermicro C9X299-PG300
- Setup: DP MST daisy chain, hotplug second monitor or have it connected on boot
- Kernel: 7.1.3 (issue observed since 6.19)
- Result: kernel oops without patch; dual monitors stable with patch

Signed-off-by: Andriy Korud <a.korud@gmail.com>
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5162
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 28ec64943e3ee4d9b8d30cea61e380f1429953a8)
Cc: stable@vger.kernel.org
This commit is contained in:
Andriy Korud 2026-07-10 12:52:26 +02:00 committed by Alex Deucher
parent cea54c52d8
commit d340cba0df
1 changed files with 6 additions and 1 deletions
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7
drivers/gpu/drm/amd/display/dc/resource/dce100/dce100_resource.c
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@ -992,6 +992,11 @@ struct stream_encoder *dce100_find_first_free_match_stream_enc_for_link(
for (i = 0; i < pool->stream_enc_count; i++) {
if (!res_ctx->is_stream_enc_acquired[i] &&
pool->stream_enc[i]) {
/* DP/MST needs a digital encoder; skip analog/no-DP encoders */
if (dc_is_dp_signal(stream->signal) &&
(!pool->stream_enc[i]->funcs ||
!pool->stream_enc[i]->funcs->dp_set_stream_attribute))
continue;
/* Store first available for MST second display
* in daisy chain use case
*/
@ -1014,7 +1019,7 @@ struct stream_encoder *dce100_find_first_free_match_stream_enc_for_link(
* required for non DP connectors.
*/
if (j >= 0 && link->connector_signal == SIGNAL_TYPE_DISPLAY_PORT)
if (j >= 0 && dc_is_dp_signal(stream->signal))
return pool->stream_enc[j];
return NULL;