drm/panel-edp: Avoid adding multiple preferred modes

If a non generic edp-panel is under aux-bus, the mode read from edid would
still be selected as preferred and results in multiple preferred modes,
which is ambiguous.

If both hard-coded mode and edid exists, only add mode from hard-coded.
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231117215056.1883314-4-hsinyi@chromium.org

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

@@ -589,6 +589,7 @@ static int panel_edp_get_modes(struct drm_panel *panel,
 {
 	struct panel_edp *p = to_panel_edp(panel);
 	int num = 0;
+	bool has_hard_coded_modes = p->desc->num_timings || p->desc->num_modes;
 	bool has_override_edid_mode = p->detected_panel &&
 				      p->detected_panel != ERR_PTR(-EINVAL) &&
 				      p->detected_panel->override_edid_mode;
@@ -599,7 +600,11 @@ static int panel_edp_get_modes(struct drm_panel *panel,
 
 		if (!p->edid)
 			p->edid = drm_get_edid(connector, p->ddc);
-		if (p->edid) {
+		/*
+		 * If both edid and hard-coded modes exists, skip edid modes to
+		 * avoid multiple preferred modes.
+		 */
+		if (p->edid && !has_hard_coded_modes) {
 			if (has_override_edid_mode) {
 				/*
 				 * override_edid_mode is specified. Use
@@ -616,12 +621,7 @@ static int panel_edp_get_modes(struct drm_panel *panel,
 		pm_runtime_put_autosuspend(panel->dev);
 	}
 
-	/*
-	 * Add hard-coded panel modes. Don't call this if there are no timings
-	 * and no modes (the generic edp-panel case) because it will clobber
-	 * the display_info that was already set by drm_add_edid_modes().
-	 */
-	if (p->desc->num_timings || p->desc->num_modes)
+	if (has_hard_coded_modes)
 		num += panel_edp_get_non_edid_modes(p, connector);
 	else if (!num)
 		dev_warn(p->base.dev, "No display modes\n");