drm/amd/display: Poll pending DOWN_REP before enabling the link

[Why]
With special monitor combination on MST, the UP_REQ could come
after clear payload table. It makes the pending DOWN_REP fail
to be handled after link training and the new DOWN_REQ will be queued
until time out .

[How]
To move the current polling pending DOWN_REP procedure to after
clear payload table to make sure the pending DOWN_REP can be
done before enabling the link.
Signed-off-by: Martin Tsai <martin.tsai@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c

@@ -264,7 +264,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 }
 
 /*
- * poll pending down reply before clear payload allocation table
+ * poll pending down reply
  */
 void dm_helpers_dp_mst_poll_pending_down_reply(
 	struct dc_context *ctx,

drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -1466,14 +1466,14 @@ static enum dc_status enable_link_dp_mst(
 	if (link->cur_link_settings.lane_count != LANE_COUNT_UNKNOWN)
 		return DC_OK;
 
+	/* clear payload table */
+	dm_helpers_dp_mst_clear_payload_allocation_table(link->ctx, link);
+
 	/* to make sure the pending down rep can be processed
-	 * before clear payload table
+	 * before enabling the link
 	 */
 	dm_helpers_dp_mst_poll_pending_down_reply(link->ctx, link);
 
-	/* clear payload table */
-	dm_helpers_dp_mst_clear_payload_allocation_table(link->ctx, link);
-
 	/* set the sink to MST mode before enabling the link */
 	dp_enable_mst_on_sink(link, true);
 

drivers/gpu/drm/amd/display/dc/dm_helpers.h

@@ -58,7 +58,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 		bool enable);
 
 /*
- * poll pending down reply before clear payload allocation table
+ * poll pending down reply
  */
 void dm_helpers_dp_mst_poll_pending_down_reply(
 	struct dc_context *ctx,