panel: Lightweight support of get_modes()

Linux uses get_modes() to fetch all available panel modes from the
driver. This is also used to fetch the modes from Linux's simple panel
implementation where a list of drm_display_mode structs is used to
define the different possible panels.

To make our work easier, create a compatible way of fetching and
defining these modes in u-boot. get_modes() fetches the available modes
from the panel driver. The get_display_timing() call maps the
drm_display_mode properties to the display_timing struct. This call now
uses whatever panel operation is available, get_display_timing() or
get_modes().

Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Markus Schneider-Pargmann (TI.com) <msp@baylibre.com>

drivers/video/panel-uclass.c

@@ -37,15 +37,47 @@ int panel_set_backlight(struct udevice *dev, int percent)
 	return ops->set_backlight(dev, percent);
 }
 
+static void drm_mode_to_display_timing(const struct drm_display_mode *mode,
+				       struct display_timing *timing)
+{
+	timing->pixelclock.typ = mode->clock * 1000; /* kHz to Hz */
+	timing->hactive.typ = mode->hdisplay;
+	timing->hfront_porch.typ = mode->hsync_start - mode->hdisplay;
+	timing->hsync_len.typ = mode->hsync_end - mode->hsync_start;
+	timing->hback_porch.typ = mode->htotal - mode->hsync_end;
+	timing->vactive.typ = mode->vdisplay;
+	timing->vfront_porch.typ = mode->vsync_start - mode->vdisplay;
+	timing->vsync_len.typ = mode->vsync_end - mode->vsync_start;
+	timing->vback_porch.typ = mode->vtotal - mode->vsync_end;
+
+	/* DRM_MODE_FLAG_* defines are already mapped to u-boot DISPLAY_FLAGS */
+	timing->flags = mode->flags;
+}
+
 int panel_get_display_timing(struct udevice *dev,
 			     struct display_timing *timings)
 {
 	struct panel_ops *ops = panel_get_ops(dev);
+	const struct drm_display_mode *modes;
+	int ret = -ENOSYS;
 
-	if (!ops->get_display_timing)
+	if (ops->get_display_timing) {
-		return -ENOSYS;
+		ret = ops->get_display_timing(dev, timings);
+		if (ret != -ENODEV)
+			return ret;
+	}
 
-	return ops->get_display_timing(dev, timings);
+	if (!ops->get_modes)
+		return ret;
+
+	ret = ops->get_modes(dev, &modes);
+	if (ret < 0)
+		return ret;
+	else if (ret == 0)
+		return -ENODEV;
+
+	drm_mode_to_display_timing(&modes[0], timings);
+	return 0;
 }
 
 UCLASS_DRIVER(panel) = {

include/panel.h

@@ -7,6 +7,62 @@
 #ifndef _PANEL_H
 #define _PANEL_H
 
+#include <video.h>
+#include <fdtdec.h>
+
+/* DRM mode flags mapped to U-Boot DISPLAY_FLAGS for direct compatibility */
+#define DRM_MODE_FLAG_NHSYNC		DISPLAY_FLAGS_HSYNC_LOW
+#define DRM_MODE_FLAG_PHSYNC		DISPLAY_FLAGS_HSYNC_HIGH
+#define DRM_MODE_FLAG_NVSYNC		DISPLAY_FLAGS_VSYNC_LOW
+#define DRM_MODE_FLAG_PVSYNC		DISPLAY_FLAGS_VSYNC_HIGH
+#define DRM_MODE_FLAG_INTERLACE		DISPLAY_FLAGS_INTERLACED
+#define DRM_MODE_FLAG_DBLSCAN		DISPLAY_FLAGS_DOUBLESCAN
+#define DRM_MODE_FLAG_DBLCLK		DISPLAY_FLAGS_DOUBLECLK
+
+/**
+ * struct drm_display_mode - DRM kernel-internal display mode structure
+ *			     simplified for U-Boot
+ * @hdisplay: horizontal display size
+ * @hsync_start: horizontal sync start
+ * @hsync_end: horizontal sync end
+ * @htotal: horizontal total size
+ * @vdisplay: vertical display size
+ * @vsync_start: vertical sync start
+ * @vsync_end: vertical sync end
+ * @vtotal: vertical total size
+ *
+ * The horizontal and vertical timings are defined per the following diagram.
+ *
+ * ::
+ *
+ *
+ *               Active                 Front           Sync           Back
+ *              Region                 Porch                          Porch
+ *     <-----------------------><----------------><-------------><-------------->
+ *       //////////////////////|
+ *      ////////////////////// |
+ *     //////////////////////  |..................               ................
+ *                                                _______________
+ *     <----- [hv]display ----->
+ *     <------------- [hv]sync_start ------------>
+ *     <--------------------- [hv]sync_end --------------------->
+ *     <-------------------------------- [hv]total ----------------------------->*
+ */
+struct drm_display_mode {
+	unsigned int clock; /* in kHz */
+
+	u16 hdisplay;
+	u16 hsync_start;
+	u16 hsync_end;
+	u16 htotal;
+	u16 vdisplay;
+	u16 vsync_start;
+	u16 vsync_end;
+	u16 vtotal;
+
+	u32 flags;
+};
+
 struct panel_ops {
 	/**
 	 * enable_backlight() - Enable the panel backlight
@@ -34,6 +90,19 @@ struct panel_ops {
 	 */
 	int (*get_display_timing)(struct udevice *dev,
 				  struct display_timing *timing);
+
+	/**
+	 * get_modes() - Get display modes from panel
+	 *
+	 * Returns an array of display modes supported by the panel.
+	 * Similar to Linux's drm_panel_funcs->get_modes().
+	 *
+	 * @dev:	Panel device
+	 * @modes:	Pointer to an array of modes
+	 * @return number of modes if OK, -ve on error
+	 */
+	int (*get_modes)(struct udevice *dev,
+			 const struct drm_display_mode **modes);
 };
 
 #define panel_get_ops(dev)	((struct panel_ops *)(dev)->driver->ops)