video: panel: Add a simple panel driver

Most panels are very simple - they just have a power supply and a backlight.
Add a driver which supports this and implements the enable_backlight()
method.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/video/Makefile

@@ -8,7 +8,7 @@
 ifdef CONFIG_DM
 obj-$(CONFIG_DISPLAY_PORT) += dp-uclass.o
 obj-$(CONFIG_DM_VIDEO) += backlight-uclass.o
-obj-$(CONFIG_DM_VIDEO) += panel-uclass.o
+obj-$(CONFIG_DM_VIDEO) += panel-uclass.o simple_panel.o
 obj-$(CONFIG_DM_VIDEO) += video-uclass.o vidconsole-uclass.o console_normal.o
 obj-$(CONFIG_DM_VIDEO) += video_bmp.o
 ifdef CONFIG_DM_VIDEO

drivers/video/simple_panel.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2016 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <backlight.h>
+#include <dm.h>
+#include <panel.h>
+#include <asm/gpio.h>
+#include <power/regulator.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct simple_panel_priv {
+	struct udevice *reg;
+	struct udevice *backlight;
+	struct gpio_desc enable;
+};
+
+static int simple_panel_enable_backlight(struct udevice *dev)
+{
+	struct simple_panel_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	dm_gpio_set_value(&priv->enable, 1);
+	ret = backlight_enable(priv->backlight);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int simple_panel_ofdata_to_platdata(struct udevice *dev)
+{
+	struct simple_panel_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
+					   "power-supply", &priv->reg);
+	if (ret) {
+		debug("%s: Warning: cnnot get power supply: ret=%d\n",
+		      __func__, ret);
+		if (ret != -ENOENT)
+			return ret;
+	}
+	ret = uclass_get_device_by_phandle(UCLASS_PANEL_BACKLIGHT, dev,
+					   "backlight", &priv->backlight);
+	if (ret) {
+		debug("%s: Cannot get backlight: ret=%d\n", __func__, ret);
+		return ret;
+	}
+	ret = gpio_request_by_name(dev, "enable-gpios", 0, &priv->enable,
+				   GPIOD_IS_OUT);
+	if (ret) {
+		debug("%s: Warning: cannot get enable GPIO: ret=%d\n",
+		      __func__, ret);
+		if (ret != -ENOENT)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int simple_panel_probe(struct udevice *dev)
+{
+	struct simple_panel_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	if (priv->reg) {
+		debug("%s: Enable regulator '%s'\n", __func__, priv->reg->name);
+		ret = regulator_set_enable(priv->reg, true);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static const struct panel_ops simple_panel_ops = {
+	.enable_backlight	= simple_panel_enable_backlight,
+};
+
+static const struct udevice_id simple_panel_ids[] = {
+	{ .compatible = "simple-panel" },
+	{ }
+};
+
+U_BOOT_DRIVER(simple_panel) = {
+	.name	= "simple_panel",
+	.id	= UCLASS_PANEL,
+	.of_match = simple_panel_ids,
+	.ops	= &simple_panel_ops,
+	.ofdata_to_platdata	= simple_panel_ofdata_to_platdata,
+	.probe		= simple_panel_probe,
+	.priv_auto_alloc_size	= sizeof(struct simple_panel_priv),
+};