diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
index 6e93a39a6fec..69a0430c4638 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic.c
@@ -206,6 +206,20 @@ intel_digital_connector_needs_modeset(struct intel_atomic_state *state,
 	       (new_crtc && drm_atomic_crtc_needs_modeset(&new_crtc_state->uapi));
 }
 
+struct intel_digital_connector_state *
+intel_atomic_get_digital_connector_state(struct intel_atomic_state *state,
+					 struct intel_connector *connector)
+{
+	struct drm_connector_state *connector_state;
+
+	connector_state = drm_atomic_get_connector_state(&state->base,
+							 &connector->base);
+	if (IS_ERR(connector_state))
+		return ERR_CAST(connector_state);
+
+	return to_intel_digital_connector_state(connector_state);
+}
+
 /**
  * intel_crtc_duplicate_state - duplicate crtc state
  * @crtc: drm crtc
diff --git a/drivers/gpu/drm/i915/display/intel_atomic.h b/drivers/gpu/drm/i915/display/intel_atomic.h
index ba9cc29a5865..6e8638d83d28 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic.h
+++ b/drivers/gpu/drm/i915/display/intel_atomic.h
@@ -35,6 +35,9 @@ struct drm_connector_state *
 intel_digital_connector_duplicate_state(struct drm_connector *connector);
 bool intel_digital_connector_needs_modeset(struct intel_atomic_state *state,
 					   struct intel_connector *connector);
+struct intel_digital_connector_state *
+intel_atomic_get_digital_connector_state(struct intel_atomic_state *state,
+					 struct intel_connector *connector);
 
 struct drm_crtc_state *intel_crtc_duplicate_state(struct drm_crtc *crtc);
 void intel_crtc_destroy_state(struct drm_crtc *crtc,
diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index 3e81c54c349e..e29bde21066e 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -1903,8 +1903,13 @@ intel_ddi_transcoder_func_reg_val_get(const struct intel_crtc_state *crtc_state)
 		temp |= TRANS_DDI_MODE_SELECT_DP_MST;
 		temp |= DDI_PORT_WIDTH(crtc_state->lane_count);
 
-		if (INTEL_GEN(dev_priv) >= 12)
-			temp |= TRANS_DDI_MST_TRANSPORT_SELECT(crtc_state->cpu_transcoder);
+		if (INTEL_GEN(dev_priv) >= 12) {
+			enum transcoder master;
+
+			master = crtc_state->mst_master_transcoder;
+			WARN_ON(master == INVALID_TRANSCODER);
+			temp |= TRANS_DDI_MST_TRANSPORT_SELECT(master);
+		}
 	} else {
 		temp |= TRANS_DDI_MODE_SELECT_DP_SST;
 		temp |= DDI_PORT_WIDTH(crtc_state->lane_count);
@@ -4375,6 +4380,11 @@ void intel_ddi_get_config(struct intel_encoder *encoder,
 		pipe_config->output_types |= BIT(INTEL_OUTPUT_DP_MST);
 		pipe_config->lane_count =
 			((temp & DDI_PORT_WIDTH_MASK) >> DDI_PORT_WIDTH_SHIFT) + 1;
+
+		if (INTEL_GEN(dev_priv) >= 12)
+			pipe_config->mst_master_transcoder =
+					REG_FIELD_GET(TRANS_DDI_MST_TRANSPORT_SELECT_MASK, temp);
+
 		intel_dp_get_m_n(intel_crtc, pipe_config);
 		break;
 	default:
diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index fe863f961067..d059948eec9a 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -46,6 +46,7 @@
 #include "display/intel_crt.h"
 #include "display/intel_ddi.h"
 #include "display/intel_dp.h"
+#include "display/intel_dp_mst.h"
 #include "display/intel_dsi.h"
 #include "display/intel_dvo.h"
 #include "display/intel_gmbus.h"
@@ -11667,6 +11668,7 @@ static void intel_crtc_state_reset(struct intel_crtc_state *crtc_state,
 	crtc_state->hsw_workaround_pipe = INVALID_PIPE;
 	crtc_state->output_format = INTEL_OUTPUT_FORMAT_INVALID;
 	crtc_state->scaler_state.scaler_id = -1;
+	crtc_state->mst_master_transcoder = INVALID_TRANSCODER;
 }
 
 /* Returns the currently programmed mode of the given encoder. */
@@ -12514,6 +12516,9 @@ static void intel_dump_pipe_config(const struct intel_crtc_state *pipe_config,
 			      pipe_config->csc_mode, pipe_config->gamma_mode,
 			      pipe_config->gamma_enable, pipe_config->csc_enable);
 
+	DRM_DEBUG_KMS("MST master transcoder: %s\n",
+		      transcoder_name(pipe_config->mst_master_transcoder));
+
 dump_planes:
 	if (!state)
 		return;
@@ -12655,6 +12660,7 @@ intel_crtc_prepare_cleared_state(struct intel_crtc_state *crtc_state)
 	memcpy(saved_state->icl_port_dplls, crtc_state->icl_port_dplls,
 	       sizeof(saved_state->icl_port_dplls));
 	saved_state->crc_enabled = crtc_state->crc_enabled;
+	saved_state->mst_master_transcoder = INVALID_TRANSCODER;
 	if (IS_G4X(dev_priv) ||
 	    IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
 		saved_state->wm = crtc_state->wm;
@@ -13290,6 +13296,8 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
 	PIPE_CONF_CHECK_I(sync_mode_slaves_mask);
 	PIPE_CONF_CHECK_I(master_transcoder);
 
+	PIPE_CONF_CHECK_I(mst_master_transcoder);
+
 #undef PIPE_CONF_CHECK_X
 #undef PIPE_CONF_CHECK_I
 #undef PIPE_CONF_CHECK_BOOL
@@ -14374,7 +14382,7 @@ static void intel_commit_modeset_disables(struct intel_atomic_state *state)
 	u32 handled = 0;
 	int i;
 
-	/* Only disable port sync slaves */
+	/* Only disable port sync and MST slaves */
 	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
 					    new_crtc_state, i) {
 		if (!needs_modeset(new_crtc_state))
@@ -14388,7 +14396,8 @@ static void intel_commit_modeset_disables(struct intel_atomic_state *state)
 		 * slave CRTCs are disabled first and then master CRTC since
 		 * Slave vblanks are masked till Master Vblanks.
 		 */
-		if (!is_trans_port_sync_slave(old_crtc_state))
+		if (!is_trans_port_sync_slave(old_crtc_state) &&
+		    !intel_dp_mst_is_slave_trans(old_crtc_state))
 			continue;
 
 		intel_pre_plane_update(state, crtc);
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 83ea04149b77..630a94892b7b 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1054,6 +1054,9 @@ struct intel_crtc_state {
 
 	/* Bitmask to indicate slaves attached */
 	u8 sync_mode_slaves_mask;
+
+	/* Only valid on TGL+ */
+	enum transcoder mst_master_transcoder;
 };
 
 struct intel_crtc {
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 926e49f449a6..12f5e799d91f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -87,6 +87,49 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
 	return 0;
 }
 
+/*
+ * Iterate over all connectors and set mst_master_transcoder to the smallest
+ * transcoder id that shares the same MST connector.
+ */
+static int
+intel_dp_mst_master_trans_compute(struct intel_encoder *encoder,
+				  struct intel_crtc_state *crtc_state,
+				  struct drm_connector_state *connector_state)
+{
+	struct intel_atomic_state *state = to_intel_atomic_state(crtc_state->uapi.state);
+	struct intel_connector *connector = to_intel_connector(connector_state->connector);
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct intel_digital_connector_state *iter_connector_state;
+	struct intel_connector *iter_connector;
+	int i;
+
+	if (INTEL_GEN(dev_priv) < 12)
+		return 0;
+
+	crtc_state->mst_master_transcoder = I915_MAX_TRANSCODERS;
+
+	for_each_new_intel_connector_in_state(state, iter_connector,
+					      iter_connector_state, i) {
+		struct intel_crtc_state *iter_crtc_state;
+		struct intel_crtc *iter_crtc;
+
+		if (connector->mst_port != iter_connector->mst_port ||
+		    !iter_connector_state->base.crtc)
+			continue;
+
+		iter_crtc = to_intel_crtc(iter_connector_state->base.crtc);
+		iter_crtc_state = intel_atomic_get_new_crtc_state(state,
+								  iter_crtc);
+		if (!iter_crtc_state->uapi.active)
+			continue;
+
+		if (iter_crtc_state->cpu_transcoder < crtc_state->mst_master_transcoder)
+			crtc_state->mst_master_transcoder = iter_crtc_state->cpu_transcoder;
+	}
+
+	return 0;
+}
+
 static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 				       struct intel_crtc_state *pipe_config,
 				       struct drm_connector_state *conn_state)
@@ -154,24 +197,88 @@ static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
 	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 
+	ret = intel_dp_mst_master_trans_compute(encoder, pipe_config,
+						conn_state);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/*
+ * If one of the connectors in a MST stream needs a modeset, mark all CRTCs
+ * that have a connector in the same MST stream as mode changed,
+ * intel_modeset_pipe_config()+intel_crtc_check_fastset() will take to do a
+ * fastset when possible.
+ */
+static int
+intel_dp_mst_atomic_master_trans_check(struct intel_connector *connector,
+				       struct intel_atomic_state *state)
+{
+	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
+	struct drm_connector_list_iter connector_list_iter;
+	struct intel_connector *connector_iter;
+
+	if (INTEL_GEN(dev_priv) < 12)
+		return  0;
+
+	if (!intel_digital_connector_needs_modeset(state, connector))
+		return 0;
+
+	drm_connector_list_iter_begin(&dev_priv->drm, &connector_list_iter);
+	for_each_intel_connector_iter(connector_iter, &connector_list_iter) {
+		struct intel_digital_connector_state *connector_iter_state;
+		struct intel_crtc_state *crtc_state;
+		struct intel_crtc *crtc;
+
+		if (connector_iter->mst_port != connector->mst_port)
+			continue;
+
+		connector_iter_state =
+			intel_atomic_get_digital_connector_state(state,
+								 connector_iter);
+		if (IS_ERR(connector_iter_state)) {
+			drm_connector_list_iter_end(&connector_list_iter);
+			return PTR_ERR(connector_iter_state);
+		}
+
+		if (!connector_iter_state->base.crtc)
+			continue;
+
+		crtc = to_intel_crtc(connector_iter_state->base.crtc);
+		crtc_state = intel_atomic_get_crtc_state(&state->base, crtc);
+		if (IS_ERR(crtc_state)) {
+			drm_connector_list_iter_end(&connector_list_iter);
+			return PTR_ERR(crtc_state);
+		}
+
+		crtc_state->uapi.mode_changed = true;
+	}
+	drm_connector_list_iter_end(&connector_list_iter);
+
 	return 0;
 }
 
 static int
 intel_dp_mst_atomic_check(struct drm_connector *connector,
-			  struct drm_atomic_state *state)
+			  struct drm_atomic_state *_state)
 {
+	struct intel_atomic_state *state = to_intel_atomic_state(_state);
 	struct drm_connector_state *new_conn_state =
-		drm_atomic_get_new_connector_state(state, connector);
+		drm_atomic_get_new_connector_state(&state->base, connector);
 	struct drm_connector_state *old_conn_state =
-		drm_atomic_get_old_connector_state(state, connector);
+		drm_atomic_get_old_connector_state(&state->base, connector);
 	struct intel_connector *intel_connector =
 		to_intel_connector(connector);
 	struct drm_crtc *new_crtc = new_conn_state->crtc;
 	struct drm_dp_mst_topology_mgr *mgr;
 	int ret;
 
-	ret = intel_digital_connector_atomic_check(connector, state);
+	ret = intel_digital_connector_atomic_check(connector, &state->base);
+	if (ret)
+		return ret;
+
+	ret = intel_dp_mst_atomic_master_trans_check(intel_connector, state);
 	if (ret)
 		return ret;
 
@@ -182,12 +289,9 @@ intel_dp_mst_atomic_check(struct drm_connector *connector,
 	 * connector
 	 */
 	if (new_crtc) {
-		struct intel_atomic_state *intel_state =
-			to_intel_atomic_state(state);
 		struct intel_crtc *intel_crtc = to_intel_crtc(new_crtc);
 		struct intel_crtc_state *crtc_state =
-			intel_atomic_get_new_crtc_state(intel_state,
-							intel_crtc);
+			intel_atomic_get_new_crtc_state(state, intel_crtc);
 
 		if (!crtc_state ||
 		    !drm_atomic_crtc_needs_modeset(&crtc_state->uapi) ||
@@ -196,7 +300,7 @@ intel_dp_mst_atomic_check(struct drm_connector *connector,
 	}
 
 	mgr = &enc_to_mst(old_conn_state->best_encoder)->primary->dp.mst_mgr;
-	ret = drm_dp_atomic_release_vcpi_slots(state, mgr,
+	ret = drm_dp_atomic_release_vcpi_slots(&state->base, mgr,
 					       intel_connector->port);
 
 	return ret;
@@ -241,6 +345,9 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
 	intel_dp->active_mst_links--;
 	last_mst_stream = intel_dp->active_mst_links == 0;
 
+	WARN_ON(INTEL_GEN(dev_priv) >= 12 && last_mst_stream &&
+		!intel_dp_mst_is_master_trans(old_crtc_state));
+
 	/*
 	 * From TGL spec: "If multi-stream slave transcoder: Configure
 	 * Transcoder Clock Select to direct no clock to the transcoder"
@@ -321,6 +428,9 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
 	intel_mst->connector = connector;
 	first_mst_stream = intel_dp->active_mst_links == 0;
 
+	WARN_ON(INTEL_GEN(dev_priv) >= 12 && first_mst_stream &&
+		!intel_dp_mst_is_master_trans(pipe_config));
+
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 
 	if (first_mst_stream)
@@ -726,3 +836,14 @@ intel_dp_mst_encoder_cleanup(struct intel_digital_port *intel_dig_port)
 	drm_dp_mst_topology_mgr_destroy(&intel_dp->mst_mgr);
 	/* encoders will get killed by normal cleanup */
 }
+
+bool intel_dp_mst_is_master_trans(const struct intel_crtc_state *crtc_state)
+{
+	return crtc_state->mst_master_transcoder == crtc_state->cpu_transcoder;
+}
+
+bool intel_dp_mst_is_slave_trans(const struct intel_crtc_state *crtc_state)
+{
+	return crtc_state->mst_master_transcoder != INVALID_TRANSCODER &&
+	       crtc_state->mst_master_transcoder != crtc_state->cpu_transcoder;
+}
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.h b/drivers/gpu/drm/i915/display/intel_dp_mst.h
index f660ad80db04..e40767f78343 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.h
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.h
@@ -6,10 +6,15 @@
 #ifndef __INTEL_DP_MST_H__
 #define __INTEL_DP_MST_H__
 
+#include <stdbool.h>
+
 struct intel_digital_port;
+struct intel_crtc_state;
 
 int intel_dp_mst_encoder_init(struct intel_digital_port *intel_dig_port, int conn_id);
 void intel_dp_mst_encoder_cleanup(struct intel_digital_port *intel_dig_port);
 int intel_dp_mst_encoder_active_links(struct intel_digital_port *intel_dig_port);
+bool intel_dp_mst_is_master_trans(const struct intel_crtc_state *crtc_state);
+bool intel_dp_mst_is_slave_trans(const struct intel_crtc_state *crtc_state);
 
 #endif /* __INTEL_DP_MST_H__ */
