dm: led: Add a driver for GPIO-controlled LEDs

Add a simple driver which allows use of LEDs attached to GPIOs. The linux
device tree binding is used.

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

doc/device-tree-bindings/leds/leds-gpio.txt

@@ -0,0 +1,52 @@
+LEDs connected to GPIO lines
+
+Required properties:
+- compatible : should be "gpio-leds".
+
+Each LED is represented as a sub-node of the gpio-leds device.  Each
+node's name represents the name of the corresponding LED.
+
+LED sub-node properties:
+- gpios :  Should specify the LED's GPIO, see "gpios property" in
+  Documentation/devicetree/bindings/gpio/gpio.txt.  Active low LEDs should be
+  indicated using flags in the GPIO specifier.
+- label :  (optional)
+  see Documentation/devicetree/bindings/leds/common.txt
+- linux,default-trigger :  (optional)
+  see Documentation/devicetree/bindings/leds/common.txt
+- default-state:  (optional) The initial state of the LED.  Valid
+  values are "on", "off", and "keep".  If the LED is already on or off
+  and the default-state property is set the to same value, then no
+  glitch should be produced where the LED momentarily turns off (or
+  on).  The "keep" setting will keep the LED at whatever its current
+  state is, without producing a glitch.  The default is off if this
+  property is not present.
+
+Examples:
+
+leds {
+	compatible = "gpio-leds";
+	hdd {
+		label = "IDE Activity";
+		gpios = <&mcu_pio 0 1>; /* Active low */
+		linux,default-trigger = "ide-disk";
+	};
+
+	fault {
+		gpios = <&mcu_pio 1 0>;
+		/* Keep LED on if BIOS detected hardware fault */
+		default-state = "keep";
+	};
+};
+
+run-control {
+	compatible = "gpio-leds";
+	red {
+		gpios = <&mpc8572 6 0>;
+		default-state = "off";
+	};
+	green {
+		gpios = <&mpc8572 7 0>;
+		default-state = "on";
+	};
+};

drivers/led/Kconfig

@@ -15,3 +15,12 @@ config SPL_LED_SUPPORT
 	  If this is acceptable and you have a need to use LEDs in SPL,
 	  enable this option. You will need to enable device tree in SPL
 	  for this to work.
+
+config LED_GPIO
+	bool "LED support for GPIO-connected LEDs"
+	depends on LED && DM_GPIO
+	help
+	  Enable support for LEDs which are connected to GPIO lines. These
+	  GPIOs may be on the SoC or some other device which provides GPIOs.
+	  The GPIO driver must used driver model. LEDs are configured using
+	  the device tree.

drivers/led/Makefile

@@ -6,3 +6,4 @@
 #
 
 obj-$(CONFIG_LED) += led-uclass.o
+obj-$(CONFIG_LED_GPIO) += led_gpio.o

drivers/led/led_gpio.c

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <led.h>
+#include <asm/gpio.h>
+#include <dm/lists.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct led_gpio_priv {
+	struct gpio_desc gpio;
+};
+
+static int gpio_led_set_on(struct udevice *dev, int on)
+{
+	struct led_gpio_priv *priv = dev_get_priv(dev);
+
+	if (!dm_gpio_is_valid(&priv->gpio))
+		return -EREMOTEIO;
+
+	return dm_gpio_set_value(&priv->gpio, on);
+}
+
+static int led_gpio_probe(struct udevice *dev)
+{
+	struct led_uclass_plat *uc_plat = dev_get_uclass_platdata(dev);
+	struct led_gpio_priv *priv = dev_get_priv(dev);
+
+	/* Ignore the top-level LED node */
+	if (!uc_plat->label)
+		return 0;
+	return gpio_request_by_name(dev, "gpios", 0, &priv->gpio, GPIOD_IS_OUT);
+}
+
+static int led_gpio_remove(struct udevice *dev)
+{
+	struct led_gpio_priv *priv = dev_get_priv(dev);
+
+	if (dm_gpio_is_valid(&priv->gpio))
+		dm_gpio_free(dev, &priv->gpio);
+
+	return 0;
+}
+
+static int led_gpio_bind(struct udevice *parent)
+{
+	const void *blob = gd->fdt_blob;
+	struct udevice *dev;
+	int node;
+	int ret;
+
+	for (node = fdt_first_subnode(blob, parent->of_offset);
+	     node > 0;
+	     node = fdt_next_subnode(blob, node)) {
+		struct led_uclass_plat *uc_plat;
+		const char *label;
+
+		label = fdt_getprop(blob, node, "label", NULL);
+		if (!label) {
+			debug("%s: node %s has no label\n", __func__,
+			      fdt_get_name(blob, node, NULL));
+			return -EINVAL;
+		}
+		ret = device_bind_driver_to_node(parent, "gpio_led",
+						 fdt_get_name(blob, node, NULL),
+						 node, &dev);
+		if (ret)
+			return ret;
+		uc_plat = dev_get_uclass_platdata(dev);
+		uc_plat->label = label;
+	}
+
+	return 0;
+}
+
+static const struct led_ops gpio_led_ops = {
+	.set_on		= gpio_led_set_on,
+};
+
+static const struct udevice_id led_gpio_ids[] = {
+	{ .compatible = "gpio-leds" },
+	{ }
+};
+
+U_BOOT_DRIVER(led_gpio) = {
+	.name	= "gpio_led",
+	.id	= UCLASS_LED,
+	.of_match = led_gpio_ids,
+	.ops	= &gpio_led_ops,
+	.priv_auto_alloc_size = sizeof(struct led_gpio_priv),
+	.bind	= led_gpio_bind,
+	.probe	= led_gpio_probe,
+	.remove	= led_gpio_remove,
+};