leds: leds-pwm: Add device tree bindings

The DT binding for the pwm-leds devices are similar to the gpio-leds type.
LEDs are represented as sub-nodes of the pwm-leds device.
The code for handling the DT boot is based on the code found in the
leds-gpio driver and adapted to use PWMs instead of GPIOs.
To avoid having custom cleanup code in case of DT boot the newly created
devm_of_pwm_get() API is used to get the correct PWM instance.

For usage see:
Documentation/devicetree/bindings/leds/leds-pwm.txt
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

Documentation/devicetree/bindings/leds/leds-pwm.txt

+LED connected to PWM
+
+Required properties:
+- compatible : should be "pwm-leds".
+
+Each LED is represented as a sub-node of the pwm-leds device.  Each
+node's name represents the name of the corresponding LED.
+
+LED sub-node properties:
+- pwms : PWM property to point to the PWM device (phandle)/port (id) and to
+  specify the period time to be used: <&phandle id period_ns>;
+- pwm-names : (optional) Name to be used by the PWM subsystem for the PWM device
+  For the pwms and pwm-names property please refer to:
+  Documentation/devicetree/bindings/pwm/pwm.txt
+- max-brightness : Maximum brightness possible for the LED
+- label :  (optional)
+  see Documentation/devicetree/bindings/leds/common.txt
+- linux,default-trigger :  (optional)
+  see Documentation/devicetree/bindings/leds/common.txt
+
+Example:
+
+twl_pwm: pwm {
+	/* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
+	compatible = "ti,twl6030-pwm";
+	#pwm-cells = <2>;
+};
+
+twl_pwmled: pwmled {
+	/* provides one PWM (id 0 for Charing indicator LED) */
+	compatible = "ti,twl6030-pwmled";
+	#pwm-cells = <2>;
+};
+
+pwmleds {
+	compatible = "pwm-leds";
+	kpad {
+		label = "omap4::keypad";
+		pwms = <&twl_pwm 0 7812500>;
+		max-brightness = <127>;
+	};
+
+	charging {
+		label = "omap4:green:chrg";
+		pwms = <&twl_pwmled 0 7812500>;
+		max-brightness = <255>;
+	};
+};

drivers/leds/leds-pwm.c

@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/platform_device.h>
+#include <linux/of_platform.h>
 #include <linux/fb.h>
 #include <linux/leds.h>
 #include <linux/err.h>
@@ -58,16 +59,74 @@ static inline size_t sizeof_pwm_leds_priv(int num_leds)
 		      (sizeof(struct led_pwm_data) * num_leds);
 }
 
+static struct led_pwm_priv *led_pwm_create_of(struct platform_device *pdev)
+{
+	struct device_node *node = pdev->dev.of_node;
+	struct device_node *child;
+	struct led_pwm_priv *priv;
+	int count, ret;
+
+	/* count LEDs in this device, so we know how much to allocate */
+	count = of_get_child_count(node);
+	if (!count)
+		return NULL;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof_pwm_leds_priv(count),
+			    GFP_KERNEL);
+	if (!priv)
+		return NULL;
+
+	for_each_child_of_node(node, child) {
+		struct led_pwm_data *led_dat = &priv->leds[priv->num_leds];
+
+		led_dat->cdev.name = of_get_property(child, "label",
+						     NULL) ? : child->name;
+
+		led_dat->pwm = devm_of_pwm_get(&pdev->dev, child, NULL);
+		if (IS_ERR(led_dat->pwm)) {
+			dev_err(&pdev->dev, "unable to request PWM for %s\n",
+				led_dat->cdev.name);
+			goto err;
+		}
+		/* Get the period from PWM core when n*/
+		led_dat->period = pwm_get_period(led_dat->pwm);
+
+		led_dat->cdev.default_trigger = of_get_property(child,
+						"linux,default-trigger", NULL);
+		of_property_read_u32(child, "max-brightness",
+				     &led_dat->cdev.max_brightness);
+
+		led_dat->cdev.brightness_set = led_pwm_set;
+		led_dat->cdev.brightness = LED_OFF;
+		led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
+
+		ret = led_classdev_register(&pdev->dev, &led_dat->cdev);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "failed to register for %s\n",
+				led_dat->cdev.name);
+			of_node_put(child);
+			goto err;
+		}
+		priv->num_leds++;
+	}
+
+	return priv;
+err:
+	while (priv->num_leds--)
+		led_classdev_unregister(&priv->leds[priv->num_leds].cdev);
+
+	return NULL;
+}
+
 static int led_pwm_probe(struct platform_device *pdev)
 {
 	struct led_pwm_platform_data *pdata = pdev->dev.platform_data;
 	struct led_pwm_priv *priv;
 	int i, ret = 0;
 
-	if (!pdata)
-		return -EBUSY;
-
-	priv = devm_kzalloc(&pdev->dev, sizeof_pwm_leds_priv(pdata->num_leds),
+	if (pdata && pdata->num_leds) {
+		priv = devm_kzalloc(&pdev->dev,
+				    sizeof_pwm_leds_priv(pdata->num_leds),
 				    GFP_KERNEL);
 		if (!priv)
 			return -ENOMEM;
@@ -79,7 +138,8 @@ static int led_pwm_probe(struct platform_device *pdev)
 			led_dat->pwm = devm_pwm_get(&pdev->dev, cur_led->name);
 			if (IS_ERR(led_dat->pwm)) {
 				ret = PTR_ERR(led_dat->pwm);
-			dev_err(&pdev->dev, "unable to request PWM for %s\n",
+				dev_err(&pdev->dev,
+					"unable to request PWM for %s\n",
 					cur_led->name);
 				goto err;
 			}
@@ -98,6 +158,11 @@ static int led_pwm_probe(struct platform_device *pdev)
 				goto err;
 		}
 		priv->num_leds = pdata->num_leds;
+	} else {
+		priv = led_pwm_create_of(pdev);
+		if (!priv)
+			return -ENODEV;
+	}
 
 	platform_set_drvdata(pdev, priv);
 
@@ -121,12 +186,19 @@ static int led_pwm_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static const struct of_device_id of_pwm_leds_match[] = {
+	{ .compatible = "pwm-leds", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
+
 static struct platform_driver led_pwm_driver = {
 	.probe		= led_pwm_probe,
 	.remove		= led_pwm_remove,
 	.driver		= {
 		.name	= "leds_pwm",
 		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(of_pwm_leds_match),
 	},
 };