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>
diff --git a/drivers/video/pwm_backlight.c b/drivers/video/pwm_backlight.c
new file mode 100644
index 0000000..de6277f
--- /dev/null
+++ b/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),
+};