drm/radeon/kms/atom: set sane defaults in atombios_get_encoder_mode()

If there was no connector mapped to the encoder, atombios_get_encoder_mode()
returned 0 which is the id for DP.  Return something sane instead based on
the encoder id.  This avoids hitting the DP paths on non-DP encoders.
Signed-off-by: NAlex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_encoders.c

@@ -595,6 +595,7 @@ atombios_digital_setup(struct drm_encoder *encoder, int action)
 int
 atombios_get_encoder_mode(struct drm_encoder *encoder)
 {
+	struct radeon_encoder *radeon_encoder = to_radeon_encoder(encoder);
 	struct drm_device *dev = encoder->dev;
 	struct radeon_device *rdev = dev->dev_private;
 	struct drm_connector *connector;
@@ -602,9 +603,20 @@ atombios_get_encoder_mode(struct drm_encoder *encoder)
 	struct radeon_connector_atom_dig *dig_connector;
 
 	connector = radeon_get_connector_for_encoder(encoder);
-	if (!connector)
-		return 0;
-
+	if (!connector) {
+		switch (radeon_encoder->encoder_id) {
+		case ENCODER_OBJECT_ID_INTERNAL_UNIPHY:
+		case ENCODER_OBJECT_ID_INTERNAL_UNIPHY1:
+		case ENCODER_OBJECT_ID_INTERNAL_UNIPHY2:
+		case ENCODER_OBJECT_ID_INTERNAL_KLDSCP_LVTMA:
+		case ENCODER_OBJECT_ID_INTERNAL_KLDSCP_DVO1:
+			return ATOM_ENCODER_MODE_DVI;
+		case ENCODER_OBJECT_ID_INTERNAL_KLDSCP_DAC1:
+		case ENCODER_OBJECT_ID_INTERNAL_KLDSCP_DAC2:
+		default:
+			return ATOM_ENCODER_MODE_CRT;
+		}
+	}
 	radeon_connector = to_radeon_connector(connector);
 
 	switch (connector->connector_type) {