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>

drivers/led/Kconfig

@@ -9,6 +9,17 @@ config LED
 	  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

drivers/led/led-uclass.c

@@ -94,6 +94,75 @@ int led_set_period(struct udevice *dev, int period_ms)
 	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);
@@ -158,10 +227,26 @@ static int led_post_probe(struct udevice *dev)
 	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,
 	.name		= "led",
 	.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
 };

include/led.h

@@ -9,6 +9,7 @@
 
 #include <stdbool.h>
 #include <cyclic.h>
+#include <dm/ofnode.h>
 
 struct udevice;
 
@@ -52,10 +53,15 @@ struct led_uc_plat {
 /**
  * struct led_uc_priv - Private data the uclass stores about each device
  *
- * @period_ms:	Flash period in milliseconds
+ * @boot_led_label:	Boot LED label
+ * @boot_led_dev:	Boot LED dev
+ * @boot_led_period:	Boot LED blink period
  */
 struct led_uc_priv {
-	int period_ms;
+#ifdef CONFIG_LED_BOOT
+	const char *boot_led_label;
+	int boot_led_period;
+#endif
 };
 
 struct led_ops {
@@ -141,4 +147,49 @@ int led_sw_set_period(struct udevice *dev, int period_ms);
 bool led_sw_is_blinking(struct udevice *dev);
 bool led_sw_on_state_change(struct udevice *dev, enum led_state_t state);
 
+#ifdef CONFIG_LED_BOOT
+
+/**
+ * led_boot_on() - turn ON the designated LED for booting
+ *
+ * Return: 0 if OK, -ve on error
+ */
+int led_boot_on(void);
+
+/**
+ * led_boot_off() - turn OFF the designated LED for booting
+ *
+ * Return: 0 if OK, -ve on error
+ */
+int led_boot_off(void);
+
+#if defined(CONFIG_LED_BLINK) || defined(CONFIG_LED_SW_BLINK)
+/**
+ * led_boot_blink() - turn ON the designated LED for booting
+ *
+ * Return: 0 if OK, -ve on error
+ */
+int led_boot_blink(void);
+
+#else
+/* If LED BLINK is not supported/enabled, fallback to LED ON */
+#define led_boot_blink led_boot_on
+#endif
+#else
+static inline int led_boot_on(void)
+{
+	return -ENOSYS;
+}
+
+static inline int led_boot_off(void)
+{
+	return -ENOSYS;
+}
+
+static inline int led_boot_blink(void)
+{
+	return -ENOSYS;
+}
+#endif
+
 #endif