1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2009,2018 Daniel Mack <daniel@zonque.org>
3 
4 #include <linux/kernel.h>
5 #include <linux/platform_device.h>
6 #include <linux/leds.h>
7 #include <linux/delay.h>
8 #include <linux/gpio/consumer.h>
9 #include <linux/slab.h>
10 #include <linux/mod_devicetable.h>
11 #include <linux/module.h>
12 #include <linux/property.h>
13 
14 #define LED_LT3593_NAME "lt3593"
15 
16 struct lt3593_led_data {
17 	struct led_classdev cdev;
18 	struct gpio_desc *gpiod;
19 };
20 
lt3593_led_set(struct led_classdev * led_cdev,enum led_brightness value)21 static int lt3593_led_set(struct led_classdev *led_cdev,
22 			   enum led_brightness value)
23 {
24 	struct lt3593_led_data *led_dat =
25 		container_of(led_cdev, struct lt3593_led_data, cdev);
26 	int pulses;
27 
28 	/*
29 	 * The LT3593 resets its internal current level register to the maximum
30 	 * level on the first falling edge on the control pin. Each following
31 	 * falling edge decreases the current level by 625uA. Up to 32 pulses
32 	 * can be sent, so the maximum power reduction is 20mA.
33 	 * After a timeout of 128us, the value is taken from the register and
34 	 * applied is to the output driver.
35 	 */
36 
37 	if (value == 0) {
38 		gpiod_set_value_cansleep(led_dat->gpiod, 0);
39 		return 0;
40 	}
41 
42 	pulses = 32 - (value * 32) / 255;
43 
44 	if (pulses == 0) {
45 		gpiod_set_value_cansleep(led_dat->gpiod, 0);
46 		mdelay(1);
47 		gpiod_set_value_cansleep(led_dat->gpiod, 1);
48 		return 0;
49 	}
50 
51 	gpiod_set_value_cansleep(led_dat->gpiod, 1);
52 
53 	while (pulses--) {
54 		gpiod_set_value_cansleep(led_dat->gpiod, 0);
55 		udelay(1);
56 		gpiod_set_value_cansleep(led_dat->gpiod, 1);
57 		udelay(1);
58 	}
59 
60 	return 0;
61 }
62 
lt3593_led_probe(struct platform_device * pdev)63 static int lt3593_led_probe(struct platform_device *pdev)
64 {
65 	struct device *dev = &pdev->dev;
66 	struct lt3593_led_data *led_data;
67 	struct fwnode_handle *child;
68 	int ret, state = LEDS_GPIO_DEFSTATE_OFF;
69 	struct led_init_data init_data = {};
70 	const char *tmp;
71 
72 	led_data = devm_kzalloc(dev, sizeof(*led_data), GFP_KERNEL);
73 	if (!led_data)
74 		return -ENOMEM;
75 
76 	if (device_get_child_node_count(dev) != 1) {
77 		dev_err(dev, "Device must have exactly one LED sub-node.");
78 		return -EINVAL;
79 	}
80 
81 	led_data->gpiod = devm_gpiod_get(dev, "lltc,ctrl", 0);
82 	if (IS_ERR(led_data->gpiod))
83 		return PTR_ERR(led_data->gpiod);
84 
85 	child = device_get_next_child_node(dev, NULL);
86 
87 	if (!fwnode_property_read_string(child, "default-state", &tmp)) {
88 		if (!strcmp(tmp, "on"))
89 			state = LEDS_GPIO_DEFSTATE_ON;
90 	}
91 
92 	led_data->cdev.brightness_set_blocking = lt3593_led_set;
93 	led_data->cdev.brightness = state ? LED_FULL : LED_OFF;
94 
95 	init_data.fwnode = child;
96 	init_data.devicename = LED_LT3593_NAME;
97 	init_data.default_label = ":";
98 
99 	ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
100 	fwnode_handle_put(child);
101 	if (ret < 0)
102 		return ret;
103 
104 	platform_set_drvdata(pdev, led_data);
105 
106 	return 0;
107 }
108 
109 static const struct of_device_id of_lt3593_leds_match[] = {
110 	{ .compatible = "lltc,lt3593", },
111 	{},
112 };
113 MODULE_DEVICE_TABLE(of, of_lt3593_leds_match);
114 
115 static struct platform_driver lt3593_led_driver = {
116 	.probe		= lt3593_led_probe,
117 	.driver		= {
118 		.name	= "leds-lt3593",
119 		.of_match_table = of_lt3593_leds_match,
120 	},
121 };
122 
123 module_platform_driver(lt3593_led_driver);
124 
125 MODULE_AUTHOR("Daniel Mack <daniel@zonque.org>");
126 MODULE_DESCRIPTION("LED driver for LT3593 controllers");
127 MODULE_LICENSE("GPL v2");
128 MODULE_ALIAS("platform:leds-lt3593");
129