dm: backlight: Add a driver for a PWM backlight

Many backlights need to use a PWM to control the brightness. Add a driver
for this. It understands the standard device tree binding.

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

drivers/video/Makefile

@@ -10,6 +10,9 @@ obj-$(CONFIG_DISPLAY_PORT) += dp-uclass.o
 obj-$(CONFIG_DM_VIDEO) += backlight-uclass.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
+obj-$(CONFIG_DM_PWM) += pwm_backlight.o
+endif
 obj-$(CONFIG_VIDEO_ROTATION) += console_rotate.o
 endif
 

drivers/video/pwm_backlight.c

@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2016 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <backlight.h>
+#include <pwm.h>
+#include <asm/gpio.h>
+#include <power/regulator.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct pwm_backlight_priv {
+	struct udevice *reg;
+	struct gpio_desc enable;
+	struct udevice *pwm;
+	uint channel;
+	uint period_ns;
+	uint default_level;
+	uint min_level;
+	uint max_level;
+};
+
+static int pwm_backlight_enable(struct udevice *dev)
+{
+	struct pwm_backlight_priv *priv = dev_get_priv(dev);
+	uint duty_cycle;
+	int ret;
+
+	debug("%s: Enable '%s', regulator '%s'\n", __func__, dev->name,
+	      priv->reg->name);
+	ret = regulator_set_enable(priv->reg, true);
+	if (ret) {
+		debug("%s: Cannot enable regulator for PWM '%s'\n", __func__,
+		      dev->name);
+		return ret;
+	}
+	mdelay(120);
+
+	duty_cycle = priv->period_ns * (priv->default_level - priv->min_level) /
+		(priv->max_level - priv->min_level + 1);
+	ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
+			     duty_cycle);
+	if (ret)
+		return ret;
+	ret = pwm_set_enable(priv->pwm, priv->channel, true);
+	if (ret)
+		return ret;
+	mdelay(10);
+	dm_gpio_set_value(&priv->enable, 1);
+
+	return 0;
+}
+
+static int pwm_backlight_ofdata_to_platdata(struct udevice *dev)
+{
+	struct pwm_backlight_priv *priv = dev_get_priv(dev);
+	struct fdtdec_phandle_args args;
+	const void *blob = gd->fdt_blob;
+	int node = dev->of_offset;
+	int index, ret, count, len;
+	const u32 *cell;
+
+	ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
+					   "power-supply", &priv->reg);
+	if (ret) {
+		debug("%s: Cannot get power supply: 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;
+	}
+	ret = fdtdec_parse_phandle_with_args(blob, node, "pwms", "#pwm-cells",
+					     0, 0, &args);
+	if (ret) {
+		debug("%s: Cannot get PWM phandle: ret=%d\n", __func__, ret);
+		return ret;
+	}
+
+	ret = uclass_get_device_by_of_offset(UCLASS_PWM, args.node, &priv->pwm);
+	if (ret) {
+		debug("%s: Cannot get PWM: ret=%d\n", __func__, ret);
+		return ret;
+	}
+	priv->channel = args.args[0];
+	priv->period_ns = args.args[1];
+
+	index = fdtdec_get_int(blob, node, "default-brightness-level", 255);
+	cell = fdt_getprop(blob, node, "brightness-levels", &len);
+	count = len / sizeof(u32);
+	if (cell && count > index) {
+		priv->default_level = fdt32_to_cpu(cell[index]);
+		priv->max_level = fdt32_to_cpu(cell[count - 1]);
+	} else {
+		priv->default_level = index;
+		priv->max_level = 255;
+	}
+
+
+	return 0;
+}
+
+static int pwm_backlight_probe(struct udevice *dev)
+{
+	return 0;
+}
+
+static const struct backlight_ops pwm_backlight_ops = {
+	.enable	= pwm_backlight_enable,
+};
+
+static const struct udevice_id pwm_backlight_ids[] = {
+	{ .compatible = "pwm-backlight" },
+	{ }
+};
+
+U_BOOT_DRIVER(pwm_backlight) = {
+	.name	= "pwm_backlight",
+	.id	= UCLASS_PANEL_BACKLIGHT,
+	.of_match = pwm_backlight_ids,
+	.ops	= &pwm_backlight_ops,
+	.ofdata_to_platdata	= pwm_backlight_ofdata_to_platdata,
+	.probe		= pwm_backlight_probe,
+	.priv_auto_alloc_size	= sizeof(struct pwm_backlight_priv),
+};