From: Andriy Korud Date: Fri, 10 Jul 2026 10:52:26 +0000 (+0200) Subject: drm/amd/display: dce100: skip non-DP stream encoders for DP MST X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d340cba0df4cf327c7e89c7c1a4e79d4771d7dd5;p=thirdparty%2Fkernel%2Flinux.git drm/amd/display: dce100: skip non-DP stream encoders for DP MST 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 Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5162 Signed-off-by: Alex Deucher (cherry picked from commit 28ec64943e3ee4d9b8d30cea61e380f1429953a8) Cc: stable@vger.kernel.org --- diff --git a/drivers/gpu/drm/amd/display/dc/resource/dce100/dce100_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dce100/dce100_resource.c index b92d4f378d602..97ea22af5d2b5 100644 --- a/drivers/gpu/drm/amd/display/dc/resource/dce100/dce100_resource.c +++ b/drivers/gpu/drm/amd/display/dc/resource/dce100/dce100_resource.c @@ -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;