drm/radeon: fix hotplug of DP to DVI|HDMI passive adapters (v2)

No need to retrain the link for passive adapters.

v2: agd5f
- no passive DP to VGA adapters, update comments
- assign radeon_connector_atom_dig after we are sure
  we have a digital connector as analog connectors
  have different private data.
- get new sink type before checking for retrain.  No
  need to check if it's no longer a DP connection.

Cc: <stable@vger.kernel.org>
Signed-off-by: NJerome Glisse <jglisse@redhat.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_connectors.c

@@ -64,15 +64,28 @@ void radeon_connector_hotplug(struct drm_connector *connector)
 
 	/* just deal with DP (not eDP) here. */
 	if (connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
-		int saved_dpms = connector->dpms;
+		struct radeon_connector_atom_dig *dig_connector =
+			radeon_connector->con_priv;
+
+		/* if existing sink type was not DP no need to retrain */
+		if (dig_connector->dp_sink_type != CONNECTOR_OBJECT_ID_DISPLAYPORT)
+			return;
 
-		/* Only turn off the display it it's physically disconnected */
+		/* first get sink type as it may be reset after (un)plug */
+		dig_connector->dp_sink_type = radeon_dp_getsinktype(radeon_connector);
+		/* don't do anything if sink is not display port, i.e.,
+		 * passive dp->(dvi|hdmi) adaptor
+		 */
+		if (dig_connector->dp_sink_type == CONNECTOR_OBJECT_ID_DISPLAYPORT) {
+			int saved_dpms = connector->dpms;
+			/* Only turn off the display if it's physically disconnected */
 			if (!radeon_hpd_sense(rdev, radeon_connector->hpd.hpd))
 				drm_helper_connector_dpms(connector, DRM_MODE_DPMS_OFF);
 			else if (radeon_dp_needs_link_train(radeon_connector))
 				drm_helper_connector_dpms(connector, DRM_MODE_DPMS_ON);
 			connector->dpms = saved_dpms;
 		}
+	}
 }
 
 static void radeon_property_change_mode(struct drm_encoder *encoder)