drm/amd/display: support access ddc for mst branch

[Why]
Megachip dockings accesses ddc line through display driver when
installing FW. Previously, we would fail every transaction because
link attached to mst branch did not have their ddc transaction type
set.

[How]
Set ddc transaction type when mst branch is connected.

Signed-off-by: Eric Yang <Eric.Yang2@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index fa56c0fc02bf512ccc67ba15413c8521d6ad41b9..a4180ba63d824cddf38eb16007ab83883decbd15 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -498,6 +498,10 @@ static bool detect_dp(
                        sink_caps->signal = SIGNAL_TYPE_DISPLAY_PORT_MST;
                        link->type = dc_connection_mst_branch;
 
+                       dal_ddc_service_set_transaction_type(
+                                                       link->ddc,
+                                                       sink_caps->transaction_type);
+
                        /*
                         * This call will initiate MST topology discovery. Which
                         * will detect MST ports and add new DRM connector DRM