led: led_pwm: Add a driver for LEDs connected to PWM

Add a driver which allows to use of LEDs connected
to PWM (Linux compatible).
MAINTAINERS: add i.vozvakhov as a maintainer of leds-pwm
C(required during new functionality adding).

Signed-off-by: Ivan Vozvakhov <i.vozvakhov@corp.mail.ru>

MAINTAINERS

@@ -899,6 +899,12 @@ F:	doc/README.kwbimage
 F:	doc/kwboot.1
 F:	tools/kwb*
 
+LED
+M:	Ivan Vozvakhov <i.vozvakhov@vk.team>
+S:	Supported
+F:	doc/device-tree-bindings/leds/leds-pwm.txt
+F:	drivers/led/led_pwm.c
+
 LOGGING
 M:	Simon Glass <sjg@chromium.org>
 S:	Maintained

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

@@ -0,0 +1,47 @@
+LEDs connected to PWM (Linux compatible)
+
+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 :  (required) LED pwm channel, see "pwms property" in
+  doc/device-tree-bindings/pwm/pwm.txt
+- label :  (optional) LED label, see "label property" in
+  doc/device-tree-bindings/led/common.txt
+- max-brightness :  (optional, unsigned, default 255) Maximum brightness possible
+  for the LED
+- active-low :  (optional, boolean, default false) For PWMs where the LED is
+  wired to supply rather than ground
+- u-boot,default-brightness :  (optional, unsigned, default 0) Initial state
+  of pwm-leds
+
+Example:
+
+leds {
+    compatible = "pwm-leds";
+    status = "okay";
+
+    blue {
+        label = "led-blue";
+        pwms = <&pwm1 0 100000 0>;
+        max-brightness = <255>;
+        u-boot,default-brightness = <127>;
+    };
+
+    green {
+        label = "led-green";
+        pwms = <&pwm2 0 100000 0>;
+        max-brightness = <255>;
+        u-boot,default-brightness = <127>;
+    };
+
+    red {
+        label = "led-red";
+        pwms = <&pwm3 0 100000 0>;
+        max-brightness = <255>;
+        u-boot,default-brightness = <127>;
+    };
+}

drivers/led/Kconfig

@@ -49,6 +49,12 @@ config LED_CORTINA
 	  This option enables support for LEDs connected to the Cortina
 	  Access CAxxxx SOCs.
 
+config LED_PWM
+	bool "LED PWM"
+	depends on LED && DM_PWM
+	help
+	  Enable support for LEDs connected to PWM.
+	  Linux compatible ofdata.
 
 config LED_BLINK
 	bool "Support LED blinking"

drivers/led/Makefile

@@ -8,5 +8,6 @@ obj-$(CONFIG_LED_BCM6328) += led_bcm6328.o
 obj-$(CONFIG_LED_BCM6358) += led_bcm6358.o
 obj-$(CONFIG_LED_BCM6753) += led_bcm6753.o
 obj-$(CONFIG_LED_BCM6858) += led_bcm6858.o
+obj-$(CONFIG_LED_PWM) += led_pwm.o
 obj-$(CONFIG_$(SPL_)LED_GPIO) += led_gpio.o
 obj-$(CONFIG_LED_CORTINA) += led_cortina.o

drivers/led/led_pwm.c

@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 VK
+ * Author: Ivan Vozvakhov <i.vozvakhov@vk.team>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <led.h>
+#include <malloc.h>
+#include <dm/lists.h>
+#include <pwm.h>
+
+#define LEDS_PWM_DRIVER_NAME	"led_pwm"
+
+struct led_pwm_priv {
+	struct udevice *pwm;
+	uint period;	/* period in ns */
+	uint duty;	/* duty cycle in ns */
+	uint channel;	/* pwm channel number */
+	bool active_low;	/* pwm polarity */
+	bool enabled;
+};
+
+static int led_pwm_enable(struct udevice *dev)
+{
+	struct led_pwm_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	ret = pwm_set_invert(priv->pwm, priv->channel, priv->active_low);
+	if (ret)
+		return ret;
+
+	ret = pwm_set_config(priv->pwm, priv->channel, priv->period, priv->duty);
+	if (ret)
+		return ret;
+
+	ret = pwm_set_enable(priv->pwm, priv->channel, true);
+	if (ret)
+		return ret;
+
+	priv->enabled = true;
+
+	return 0;
+}
+
+static int led_pwm_disable(struct udevice *dev)
+{
+	struct led_pwm_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	ret = pwm_set_config(priv->pwm, priv->channel, priv->period, 0);
+	if (ret)
+		return ret;
+
+	ret = pwm_set_enable(priv->pwm, priv->channel, false);
+	if (ret)
+		return ret;
+
+	priv->enabled = false;
+
+	return 0;
+}
+
+static int led_pwm_set_state(struct udevice *dev, enum led_state_t state)
+{
+	struct led_pwm_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	switch (state) {
+	case LEDST_OFF:
+		ret = led_pwm_disable(dev);
+		break;
+	case LEDST_ON:
+		ret = led_pwm_enable(dev);
+		break;
+	case LEDST_TOGGLE:
+		ret = (priv->enabled) ? led_pwm_disable(dev) : led_pwm_enable(dev);
+		break;
+	default:
+		ret = -ENOSYS;
+	}
+
+	return ret;
+}
+
+static enum led_state_t led_pwm_get_state(struct udevice *dev)
+{
+	struct led_pwm_priv *priv = dev_get_priv(dev);
+
+	return (priv->enabled) ? LEDST_ON : LEDST_OFF;
+}
+
+static int led_pwm_probe(struct udevice *dev)
+{
+	struct led_pwm_priv *priv = dev_get_priv(dev);
+	struct led_uc_plat *uc_plat = dev_get_uclass_plat(dev);
+
+	/* Ignore the top-level LED node */
+	if (!uc_plat->label)
+		return 0;
+
+	return led_pwm_set_state(dev, (priv->enabled) ? LEDST_ON : LEDST_OFF);
+}
+
+static int led_pwm_of_to_plat(struct udevice *dev)
+{
+	struct led_uc_plat *uc_plat = dev_get_uclass_plat(dev);
+	struct led_pwm_priv *priv = dev_get_priv(dev);
+	struct ofnode_phandle_args args;
+	uint def_brightness, max_brightness;
+	int ret;
+
+	/* Ignore the top-level LED node */
+	if (!uc_plat->label)
+		return 0;
+
+	ret = dev_read_phandle_with_args(dev, "pwms", "#pwm-cells", 0, 0, &args);
+	if (ret)
+		return ret;
+
+	ret = uclass_get_device_by_ofnode(UCLASS_PWM, args.node, &priv->pwm);
+	if (ret)
+		return ret;
+
+	priv->channel = args.args[0];
+	priv->period = args.args[1];
+	priv->active_low = dev_read_bool(dev, "active-low");
+
+	def_brightness = dev_read_u32_default(dev, "u-boot,default-brightness", 0);
+	max_brightness = dev_read_u32_default(dev, "max-brightness", 255);
+	priv->enabled =  !!def_brightness;
+
+	/*
+	 * No need to handle pwm iverted case (active_low)
+	 * because of pwm_set_invert function
+	 */
+	if (def_brightness < max_brightness)
+		priv->duty = priv->period * def_brightness / max_brightness;
+	else
+		priv->duty = priv->period;
+
+	return 0;
+}
+
+static int led_pwm_bind(struct udevice *parent)
+{
+	struct udevice *dev;
+	ofnode node;
+	int ret;
+
+	dev_for_each_subnode(node, parent) {
+		struct led_uc_plat *uc_plat;
+		const char *label;
+
+		label = ofnode_read_string(node, "label");
+		if (!label)
+			label = ofnode_get_name(node);
+
+		ret = device_bind_driver_to_node(parent, LEDS_PWM_DRIVER_NAME,
+						 ofnode_get_name(node),
+						 node, &dev);
+		if (ret)
+			return ret;
+
+		uc_plat = dev_get_uclass_plat(dev);
+		uc_plat->label = label;
+	}
+	return 0;
+}
+
+static const struct led_ops led_pwm_ops = {
+	.set_state = led_pwm_set_state,
+	.get_state = led_pwm_get_state,
+};
+
+static const struct udevice_id led_pwm_ids[] = {
+	{ .compatible = "pwm-leds" },
+	{ }
+};
+
+U_BOOT_DRIVER(led_pwm) = {
+	.name = LEDS_PWM_DRIVER_NAME,
+	.id = UCLASS_LED,
+	.of_match = led_pwm_ids,
+	.ops = &led_pwm_ops,
+	.priv_auto = sizeof(struct led_pwm_priv),
+	.bind = led_pwm_bind,
+	.probe = led_pwm_probe,
+	.of_to_plat = led_pwm_of_to_plat,
+};