drm/amdgpu/display/mst: update mst_mgr relevant variable when long HPD

[Why & How]
Now the vc_start_slot is controlled at drm side. When we
service a long HPD, we still need to run
dm_helpers_dp_mst_write_payload_allocation_table() to update
drm mst_mgr's relevant variable. Otherwise, on the next plug-in,
payload will get assigned with a wrong start slot.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/2171
Signed-off-by: Wayne Lin <[e-mail]>
Signed-off-by: Harry Wentland <[e-mail]>
Fixes: 4d07b0bc4034 ("drm/display/dp_mst: Move all payload info into the atomic state")
Cc: [e-mail] # 6.1
Acked-by: Harry Wentland <[e-mail]>
Reviewed-by: Lyude Paul <[e-mail]>
Tested-by: Didier Raboud <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 	struct fixed31_32 avg_time_slots_per_mtp = dc_fixpt_from_int(0);
 	int i;
 	bool mst_mode = (link->type == dc_connection_mst_branch);
+	/* adjust for drm changes*/
+	bool update_drm_mst_state = true;
 	const struct link_hwss *link_hwss = get_link_hwss(link, &pipe_ctx->link_res);
 	const struct dc_link_settings empty_link_settings = {0};
 	DC_LOGGER_INIT(link->ctx->logger);
+
 
 	/* deallocate_mst_payload is called before disable link. When mode or
 	 * disable/enable monitor, new stream is created which is not in link
···
 				&empty_link_settings,
 				avg_time_slots_per_mtp);
 
-	if (mst_mode) {
+	if (mst_mode || update_drm_mst_state) {
 		/* when link is in mst mode, reply on mst manager to remove
 		 * payload
 		 */
···
 			stream->ctx,
 			stream);
 
+		if (!update_drm_mst_state)
+			dm_helpers_dp_mst_send_payload_allocation(
+				stream->ctx,
+				stream,
+				false);
+	}
+
+	if (update_drm_mst_state)
 		dm_helpers_dp_mst_send_payload_allocation(
 			stream->ctx,
 			stream,
 			false);
-	}
 
 	return DC_OK;
 }