drm/nouveau: default to 8bpc for non-LVDS panels if EDID isn't useful

commit c8435362 upstream.

A few reports of bad behaviour since the autodetection defaulted to 6bpc,
lets fix this.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/nouveau/nouveau_connector.c

@@ -616,10 +616,13 @@ nouveau_connector_detect_depth(struct drm_connector *connector)
 	if (nv_connector->edid && connector->display_info.bpc)
 		return;
 
-	/* if not, we're out of options unless we're LVDS, default to 6bpc */
-	connector->display_info.bpc = 6;
-	if (nv_encoder->dcb->type != OUTPUT_LVDS)
+	/* if not, we're out of options unless we're LVDS, default to 8bpc */
+	if (nv_encoder->dcb->type != OUTPUT_LVDS) {
+		connector->display_info.bpc = 8;
 		return;
+	}
+
+	connector->display_info.bpc = 6;
 
 	/* LVDS: panel straps */
 	if (bios->fp_no_ddc) {