DRM/Radeon: On DVI-I use Load Detection when EDID is bogus.

The Radeon driver uses the analog/digital flag to determine if the
DAC or the TMDS encoder should be enabled on a DVI-I connector.
If the EDID is bogus this flag is no longer reliable. This fix
adds a fallback to DAC load detection to determine if anything
is connected to the DAC. If not and a (bogus) EDID is found it
assumes a digital display is connected.
This works around problems with some crappy IPMI devices using
Radeon ES1000.
Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_connectors.c

@@ -941,7 +941,7 @@ radeon_dvi_detect(struct drm_connector *connector, bool force)
 	struct drm_mode_object *obj;
 	int i;
 	enum drm_connector_status ret = connector_status_disconnected;
-	bool dret = false;
+	bool dret = false, broken_edid = false;
 
 	if (!force && radeon_check_hpd_status_unchanged(connector))
 		return connector->status;
@@ -965,6 +965,9 @@ radeon_dvi_detect(struct drm_connector *connector, bool force)
 				ret = connector_status_disconnected;
 				DRM_ERROR("%s: detected RS690 floating bus bug, stopping ddc detect\n", drm_get_connector_name(connector));
 				radeon_connector->ddc_bus = NULL;
+			} else {
+				ret = connector_status_connected;
+				broken_edid = true; /* defer use_digital to later */
 			}
 		} else {
 			radeon_connector->use_digital = !!(radeon_connector->edid->input & DRM_EDID_INPUT_DIGITAL);
@@ -1047,13 +1050,24 @@ radeon_dvi_detect(struct drm_connector *connector, bool force)
 
 			encoder_funcs = encoder->helper_private;
 			if (encoder_funcs->detect) {
-				if (ret != connector_status_connected) {
-					ret = encoder_funcs->detect(encoder, connector);
-					if (ret == connector_status_connected) {
-						radeon_connector->use_digital = false;
+				if (!broken_edid) {
+					if (ret != connector_status_connected) {
+						/* deal with analog monitors without DDC */
+						ret = encoder_funcs->detect(encoder, connector);
+						if (ret == connector_status_connected) {
+							radeon_connector->use_digital = false;
+						}
+						if (ret != connector_status_disconnected)
+							radeon_connector->detected_by_load = true;
 					}
-					if (ret != connector_status_disconnected)
-						radeon_connector->detected_by_load = true;
+				} else {
+					enum drm_connector_status lret;
+					/* assume digital unless load detected otherwise */
+					radeon_connector->use_digital = true;
+					lret = encoder_funcs->detect(encoder, connector);
+					DRM_DEBUG_KMS("load_detect %x returned: %x\n",encoder->encoder_type,lret);
+					if (lret == connector_status_connected)
+						radeon_connector->use_digital = false;
 				}
 				break;
 			}