[PATCH AUTOSEL 6.10 077/121] drm/amd/display: use preferred link settings for dp signal only

[Sasha Levin]

From: Wenjing Liu <wenjing.liu at amd.com>

[ Upstream commit abf34ca465f5cd182b07701d3f3d369c0fc04723 ]

[why]
We set preferred link settings for virtual signal. However we don't support
virtual signal for UHBR link rate. If preferred is set to UHBR link rate, we
will allow virtual signal with UHBR link rate which causes system crashes.

Reviewed-by: Dillon Varone <dillon.varone at amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed at amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu at amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler at amd.com>
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 .../dc/link/protocols/link_dp_capability.c    | 24 ++++++++-----------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
index b26faed3bb206..a3df1b55e48b7 100644
--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
@@ -914,21 +914,17 @@ bool link_decide_link_settings(struct dc_stream_state *stream,
 
 	memset(link_setting, 0, sizeof(*link_setting));
 
-	/* if preferred is specified through AMDDP, use it, if it's enough
-	 * to drive the mode
-	 */
-	if (link->preferred_link_setting.lane_count !=
-			LANE_COUNT_UNKNOWN &&
-			link->preferred_link_setting.link_rate !=
-					LINK_RATE_UNKNOWN) {
+	if (dc_is_dp_signal(stream->signal)  &&
+			link->preferred_link_setting.lane_count != LANE_COUNT_UNKNOWN &&
+			link->preferred_link_setting.link_rate != LINK_RATE_UNKNOWN) {
+		/* if preferred is specified through AMDDP, use it, if it's enough
+		 * to drive the mode
+		 */
 		*link_setting = link->preferred_link_setting;
-		return true;
-	}
-
-	/* MST doesn't perform link training for now
-	 * TODO: add MST specific link training routine
-	 */
-	if (stream->signal == SIGNAL_TYPE_DISPLAY_PORT_MST) {
+	} else if (stream->signal == SIGNAL_TYPE_DISPLAY_PORT_MST) {
+		/* MST doesn't perform link training for now
+		 * TODO: add MST specific link training routine
+		 */
 		decide_mst_link_settings(link, link_setting);
 	} else if (link->connector_signal == SIGNAL_TYPE_EDP) {
 		/* enable edp link optimization for DSC eDP case */
-- 
2.43.0