drm/panel: lvds: Simplify mode parsing

The mode parsing is currently implemented in three steps:
of_get_display_timing() - DT panel-timing to struct display_timing
videomode_from_timing() - struct display_timing to struct videomode
drm_display_mode_from_videomode() - struct videomode to struct drm_display_mode

Replace all that with simple of_get_drm_panel_display_mode() call,
which already populates struct drm_display_mode and then duplicate
that mode in panel_lvds_get_modes() each time, since the mode does
not change.

Nice bonus is the bus_flags parsed by of_get_drm_panel_display_mode()
out of panel-timing DT node, which is used in subsequent patch to fix
handling of 'de-active' DT property.
Tested-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dmitry Osipenko <digetx@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
To: dri-devel@lists.freedesktop.org
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220401162154.295152-1-marex@denx.de

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

@@ -30,7 +30,8 @@ struct panel_lvds {
 	const char *label;
 	unsigned int width;
 	unsigned int height;
-	struct videomode video_mode;
+	struct drm_display_mode dmode;
+	u32 bus_flags;
 	unsigned int bus_format;
 	bool data_mirror;
 
@@ -87,16 +88,15 @@ static int panel_lvds_get_modes(struct drm_panel *panel,
 	struct panel_lvds *lvds = to_panel_lvds(panel);
 	struct drm_display_mode *mode;
 
-	mode = drm_mode_create(connector->dev);
+	mode = drm_mode_duplicate(connector->dev, &lvds->dmode);
 	if (!mode)
 		return 0;
 
-	drm_display_mode_from_videomode(&lvds->video_mode, mode);
 	mode->type |= DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
 	drm_mode_probed_add(connector, mode);
 
-	connector->display_info.width_mm = lvds->width;
-	connector->display_info.height_mm = lvds->height;
+	connector->display_info.width_mm = lvds->dmode.width_mm;
+	connector->display_info.height_mm = lvds->dmode.height_mm;
 	drm_display_info_set_bus_formats(&connector->display_info,
 					 &lvds->bus_format, 1);
 	connector->display_info.bus_flags = lvds->data_mirror
@@ -116,7 +116,6 @@ static const struct drm_panel_funcs panel_lvds_funcs = {
 static int panel_lvds_parse_dt(struct panel_lvds *lvds)
 {
 	struct device_node *np = lvds->dev->of_node;
-	struct display_timing timing;
 	int ret;
 
 	ret = of_drm_get_panel_orientation(np, &lvds->orientation);
@@ -125,23 +124,20 @@ static int panel_lvds_parse_dt(struct panel_lvds *lvds)
 		return ret;
 	}
 
-	ret = of_get_display_timing(np, "panel-timing", &timing);
+	ret = of_get_drm_panel_display_mode(np, &lvds->dmode, &lvds->bus_flags);
 	if (ret < 0) {
 		dev_err(lvds->dev, "%pOF: problems parsing panel-timing (%d)\n",
 			np, ret);
 		return ret;
 	}
 
-	videomode_from_timing(&timing, &lvds->video_mode);
-
-	ret = of_property_read_u32(np, "width-mm", &lvds->width);
-	if (ret < 0) {
+	if (lvds->dmode.width_mm == 0) {
 		dev_err(lvds->dev, "%pOF: invalid or missing %s DT property\n",
 			np, "width-mm");
 		return -ENODEV;
 	}
-	ret = of_property_read_u32(np, "height-mm", &lvds->height);
-	if (ret < 0) {
+
+	if (lvds->dmode.height_mm == 0) {
 		dev_err(lvds->dev, "%pOF: invalid or missing %s DT property\n",
 			np, "height-mm");
 		return -ENODEV;