drm/radeon: add DisplayPort MST support (v2)

This adds initial DP 1.2 MST support to radeon, on CAYMAN
and up in theory.

This is off by default.

v2: agd5f:
- add UNIPHY3 offsets
- move atom cmd table code into atombios_encoders.c
- whitespace cleanup
- replace some magic numbers with proper defines

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
index 3a29703..ef99917 100644
--- a/drivers/gpu/drm/radeon/radeon_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_encoders.c
@@ -247,7 +247,16 @@
 
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
 		radeon_connector = to_radeon_connector(connector);
-		if (radeon_encoder->active_device & radeon_connector->devices)
+		if (radeon_encoder->is_mst_encoder) {
+			struct radeon_encoder_mst *mst_enc;
+
+			if (!radeon_connector->is_mst_connector)
+				continue;
+
+			mst_enc = radeon_encoder->enc_priv;
+			if (mst_enc->connector == radeon_connector->mst_port)
+				return connector;
+		} else if (radeon_encoder->active_device & radeon_connector->devices)
 			return connector;
 	}
 	return NULL;
@@ -393,6 +402,9 @@
 	case DRM_MODE_CONNECTOR_DVID:
 	case DRM_MODE_CONNECTOR_HDMIA:
 	case DRM_MODE_CONNECTOR_DisplayPort:
+		if (radeon_connector->is_mst_connector)
+			return false;
+
 		dig_connector = radeon_connector->con_priv;
 		if ((dig_connector->dp_sink_type == CONNECTOR_OBJECT_ID_DISPLAYPORT) ||
 		    (dig_connector->dp_sink_type == CONNECTOR_OBJECT_ID_eDP))