drm/panel: simple: Add display timing support

The simple panel driver's ->get_modes() implementation calculates the
display mode list from the typical timings and the ->get_timings()
implementation returns the timings to the connected encoder for mode
validation and fixup.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
[treding@nvidia.com: select VIDEOMODE_HELPERS]
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/panel/Kconfig

@@ -11,6 +11,7 @@ config DRM_PANEL_SIMPLE
 	tristate "support for simple panels"
 	depends on OF
 	depends on BACKLIGHT_CLASS_DEVICE
+	select VIDEOMODE_HELPERS
 	help
 	  DRM panel driver for dumb panels that need at most a regulator and
 	  a GPIO to be powered up. Optionally a backlight can be attached so

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

@@ -33,9 +33,14 @@
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_panel.h>
 
+#include <video/display_timing.h>
+#include <video/videomode.h>
+
 struct panel_desc {
 	const struct drm_display_mode *modes;
 	unsigned int num_modes;
+	const struct display_timing *timings;
+	unsigned int num_timings;
 
 	unsigned int bpc;
 
@@ -94,6 +99,25 @@ static int panel_simple_get_fixed_modes(struct panel_simple *panel)
 	if (!panel->desc)
 		return 0;
 
+	for (i = 0; i < panel->desc->num_timings; i++) {
+		const struct display_timing *dt = &panel->desc->timings[i];
+		struct videomode vm;
+
+		videomode_from_timing(dt, &vm);
+		mode = drm_mode_create(drm);
+		if (!mode) {
+			dev_err(drm->dev, "failed to add mode %ux%u\n",
+				dt->hactive.typ, dt->vactive.typ);
+			continue;
+		}
+
+		drm_display_mode_from_videomode(&vm, mode);
+		drm_mode_set_name(mode);
+
+		drm_mode_probed_add(connector, mode);
+		num++;
+	}
+
 	for (i = 0; i < panel->desc->num_modes; i++) {
 		const struct drm_display_mode *m = &panel->desc->modes[i];
 
@@ -226,12 +250,30 @@ static int panel_simple_get_modes(struct drm_panel *panel)
 	return num;
 }
 
+static int panel_simple_get_timings(struct drm_panel *panel,
+				    unsigned int num_timings,
+				    struct display_timing *timings)
+{
+	struct panel_simple *p = to_panel_simple(panel);
+	unsigned int i;
+
+	if (p->desc->num_timings < num_timings)
+		num_timings = p->desc->num_timings;
+
+	if (timings)
+		for (i = 0; i < num_timings; i++)
+			timings[i] = p->desc->timings[i];
+
+	return p->desc->num_timings;
+}
+
 static const struct drm_panel_funcs panel_simple_funcs = {
 	.disable = panel_simple_disable,
 	.unprepare = panel_simple_unprepare,
 	.prepare = panel_simple_prepare,
 	.enable = panel_simple_enable,
 	.get_modes = panel_simple_get_modes,
+	.get_timings = panel_simple_get_timings,
 };
 
 static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)