drm/amd/display: Fix for tile MST

- Set stream signal type to be SST when setting non-tile timing on MST
  tiled display.
  - Disable MST on sink after disabling MST link.
  - Enable MST on sink before enabling MST link.
Signed-off-by: Ding Wang <Ding.Wang@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1250,6 +1250,9 @@ static enum dc_status enable_link_dp_mst(struct pipe_ctx *pipe_ctx)
 	if (link->public.cur_link_settings.lane_count != LANE_COUNT_UNKNOWN)
 		return DC_OK;
 
+	/* set the sink to MST mode before enabling the link */
+	dp_enable_mst_on_sink(link, true);
+
 	return enable_link_dp(pipe_ctx);
 }
 

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

@@ -2453,3 +2453,16 @@ bool dc_link_dp_set_test_pattern(
 
 	return true;
 }
+
+void dp_enable_mst_on_sink(struct core_link *link, bool enable)
+{
+	unsigned char mstmCntl;
+
+	core_link_read_dpcd(link, DP_MSTM_CTRL, &mstmCntl, 1);
+	if (enable)
+		mstmCntl |= DP_MST_EN;
+	else
+		mstmCntl &= (~DP_MST_EN);
+
+	core_link_write_dpcd(link, DP_MSTM_CTRL, &mstmCntl, 1);
+}

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

@@ -129,6 +129,9 @@ void dp_disable_link_phy_mst(struct core_link *link, enum signal_type signal)
 		return;
 
 	dp_disable_link_phy(link, signal);
+
+	/* set the sink to SST mode after disabling the link */
+	dp_enable_mst_on_sink(link, false);
 }
 
 bool dp_set_hw_training_pattern(

drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h

@@ -57,4 +57,6 @@ void detect_dp_sink_caps(struct core_link *link);
 
 bool is_dp_active_dongle(const struct core_link *link);
 
+void dp_enable_mst_on_sink(struct core_link *link, bool enable);
+
 #endif /* __DC_LINK_DP_H__ */