led: implement LED boot API

Implement LED boot API to signal correct boot of the system.

led_boot_on/off/blink() are introduced to turn ON, OFF and BLINK the
designated boot LED.

New Kconfig is introduced, CONFIG_LED_BOOT to enable the feature.
This makes use of the /options/u-boot property "boot-led" to the
define the boot LED.
It's also introduced a new /options/u-boot property "boot-led-period"
to define the default period when the LED is set to blink mode.

If "boot-led-period" is not defined, the value of 250 (ms) is
used by default.

If CONFIG_LED_BLINK or CONFIG_LED_SW_BLINK is not enabled,
led_boot_blink call will fallback to simple LED ON.

To cache the data we repurpose the now unused led_uc_priv for storage of
global LED uclass info.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/led/Kconfig b/drivers/led/Kconfig
index bee74b2..59b007a 100644
--- a/drivers/led/Kconfig
+++ b/drivers/led/Kconfig
@@ -9,6 +9,17 @@
 	  can provide access to board-specific LEDs. Use of the device tree
 	  for configuration is encouraged.
 
+config LED_BOOT
+	bool "Enable LED boot support"
+	help
+	  Enable LED boot support.
+
+	  LED boot is a specific LED assigned to signal boot operation status.
+	  Defined in Device Tree /options/u-boot node. Refer here for the supported
+	  options [1].
+
+	  [1] dtschema/schemas/options/u-boot.yaml
+
 config LED_BCM6328
 	bool "LED Support for BCM6328"
 	depends on LED && ARCH_BMIPS
diff --git a/drivers/led/led-uclass.c b/drivers/led/led-uclass.c
index 199d68b..5411321 100644
--- a/drivers/led/led-uclass.c
+++ b/drivers/led/led-uclass.c
@@ -94,6 +94,75 @@
 	return -ENOSYS;
 }
 
+#ifdef CONFIG_LED_BOOT
+static int led_boot_get(struct udevice **devp, int *period_ms)
+{
+	struct led_uc_priv *priv;
+	struct uclass *uc;
+	int ret;
+
+	ret = uclass_get(UCLASS_LED, &uc);
+	if (ret)
+		return ret;
+
+	priv = uclass_get_priv(uc);
+	if (!priv->boot_led_label)
+		return -ENOENT;
+
+	if (period_ms)
+		*period_ms = priv->boot_led_period;
+
+	return led_get_by_label(priv->boot_led_label, devp);
+}
+
+int led_boot_on(void)
+{
+	struct udevice *dev;
+	int ret;
+
+	ret = led_boot_get(&dev, NULL);
+	if (ret)
+		return ret;
+
+	return led_set_state(dev, LEDST_ON);
+}
+
+int led_boot_off(void)
+{
+	struct udevice *dev;
+	int ret;
+
+	ret = led_boot_get(&dev, NULL);
+	if (ret)
+		return ret;
+
+	return led_set_state(dev, LEDST_OFF);
+}
+
+#if defined(CONFIG_LED_BLINK) || defined(CONFIG_LED_SW_BLINK)
+int led_boot_blink(void)
+{
+	struct udevice *dev;
+	int period_ms, ret;
+
+	ret = led_boot_get(&dev, &period_ms);
+	if (ret)
+		return ret;
+
+	ret = led_set_period(dev, period_ms);
+	if (ret) {
+		if (ret != -ENOSYS)
+			return ret;
+
+		/* fallback to ON with no set_period and no SW_BLINK */
+		return led_set_state(dev, LEDST_ON);
+	}
+
+	return led_set_state(dev, LEDST_BLINK);
+}
+#endif
+#endif
+
 static int led_post_bind(struct udevice *dev)
 {
 	struct led_uc_plat *uc_plat = dev_get_uclass_plat(dev);
@@ -157,6 +226,18 @@
 
 	return ret;
 }
+
+#ifdef CONFIG_LED_BOOT
+static int led_init(struct uclass *uc)
+{
+	struct led_uc_priv *priv = uclass_get_priv(uc);
+
+	priv->boot_led_label = ofnode_options_read_str("boot-led");
+	priv->boot_led_period = ofnode_options_read_int("boot-led-period", 250);
+
+	return 0;
+}
+#endif
 
 UCLASS_DRIVER(led) = {
 	.id		= UCLASS_LED,
@@ -164,4 +245,8 @@
 	.per_device_plat_auto	= sizeof(struct led_uc_plat),
 	.post_bind	= led_post_bind,
 	.post_probe	= led_post_probe,
+#ifdef CONFIG_LED_BOOT
+	.init		= led_init,
+	.priv_auto	= sizeof(struct led_uc_priv),
+#endif
 };