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

BugLink: https://bugs.launchpad.net/bugs/1836117
[ Upstream commit 0a14544661fad1606cc96aece30b2950fd9c4c81 ]

[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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.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 02dcb839e467dd105217077355be2a5cffe85642..68c140ecc0814677324c0acd54b5606481c0ead3 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -484,6 +484,10 @@ static void 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