drm/panel: panel-simple: add default connector_type

All panels shall report a connector type.
panel-simple has a lot of panels with no connector_type,
and for these fall back to DPI as the default.

v2:
  - Rebased on top of validation of panel description
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200726203324.3722593-3-sam@ravnborg.org

drivers/gpu/drm/panel/panel-simple.c

@@ -500,6 +500,7 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 	struct panel_simple *panel;
 	struct display_timing dt;
 	struct device_node *ddc;
+	int connector_type;
 	u32 bus_flags;
 	int err;
 
@@ -550,10 +551,12 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 			panel_simple_parse_panel_timing_node(dev, panel, &dt);
 	}
 
+	connector_type = desc->connector_type;
 	/* Catch common mistakes for panels. */
-	switch (desc->connector_type) {
+	switch (connector_type) {
 	case 0:
 		dev_warn(dev, "Specify missing connector_type\n");
+		connector_type = DRM_MODE_CONNECTOR_DPI;
 		break;
 	case DRM_MODE_CONNECTOR_LVDS:
 		WARN_ON(desc->bus_flags &
@@ -600,11 +603,11 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 		break;
 	default:
 		dev_warn(dev, "Specify a valid connector_type: %d\n", desc->connector_type);
+		connector_type = DRM_MODE_CONNECTOR_DPI;
 		break;
 	}
 
-	drm_panel_init(&panel->base, dev, &panel_simple_funcs,
-		       desc->connector_type);
+	drm_panel_init(&panel->base, dev, &panel_simple_funcs, connector_type);
 
 	err = drm_panel_of_backlight(&panel->base);
 	if (err)