leds-lt3593.c revision 7c7d2a26dbb336ddabe53818750f4c32e2b45ddd 
1/*
2 * LEDs driver for LT3593 controllers
3 *
4 * See the datasheet at http://cds.linear.com/docs/Datasheet/3593f.pdf
5 *
6 * Copyright (c) 2009 Daniel Mack <daniel@caiaq.de>
7 *
8 * Based on leds-gpio.c,
9 *
10 *   Copyright (C) 2007 8D Technologies inc.
11 *   Raphael Assenat <raph@8d.com>
12 *   Copyright (C) 2008 Freescale Semiconductor, Inc.
13 *
14 * This program is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License version 2 as
16 * published by the Free Software Foundation.
17 */
18
19#include <linux/kernel.h>
20#include <linux/platform_device.h>
21#include <linux/leds.h>
22#include <linux/workqueue.h>
23#include <linux/delay.h>
24#include <linux/gpio.h>
25#include <linux/slab.h>
26#include <linux/module.h>
27
28struct lt3593_led_data {
29	struct led_classdev cdev;
30	unsigned gpio;
31	struct work_struct work;
32	u8 new_level;
33};
34
35static void lt3593_led_work(struct work_struct *work)
36{
37	int pulses;
38	struct lt3593_led_data *led_dat =
39		container_of(work, struct lt3593_led_data, work);
40
41	/*
42	 * The LT3593 resets its internal current level register to the maximum
43	 * level on the first falling edge on the control pin. Each following
44	 * falling edge decreases the current level by 625uA. Up to 32 pulses
45	 * can be sent, so the maximum power reduction is 20mA.
46	 * After a timeout of 128us, the value is taken from the register and
47	 * applied is to the output driver.
48	 */
49
50	if (led_dat->new_level == 0) {
51		gpio_set_value_cansleep(led_dat->gpio, 0);
52		return;
53	}
54
55	pulses = 32 - (led_dat->new_level * 32) / 255;
56
57	if (pulses == 0) {
58		gpio_set_value_cansleep(led_dat->gpio, 0);
59		mdelay(1);
60		gpio_set_value_cansleep(led_dat->gpio, 1);
61		return;
62	}
63
64	gpio_set_value_cansleep(led_dat->gpio, 1);
65
66	while (pulses--) {
67		gpio_set_value_cansleep(led_dat->gpio, 0);
68		udelay(1);
69		gpio_set_value_cansleep(led_dat->gpio, 1);
70		udelay(1);
71	}
72}
73
74static void lt3593_led_set(struct led_classdev *led_cdev,
75	enum led_brightness value)
76{
77	struct lt3593_led_data *led_dat =
78		container_of(led_cdev, struct lt3593_led_data, cdev);
79
80	led_dat->new_level = value;
81	schedule_work(&led_dat->work);
82}
83
84static int create_lt3593_led(const struct gpio_led *template,
85	struct lt3593_led_data *led_dat, struct device *parent)
86{
87	int ret, state;
88
89	/* skip leds on GPIOs that aren't available */
90	if (!gpio_is_valid(template->gpio)) {
91		dev_info(parent, "%s: skipping unavailable LT3593 LED at gpio %d (%s)\n",
92				KBUILD_MODNAME, template->gpio, template->name);
93		return 0;
94	}
95
96	led_dat->cdev.name = template->name;
97	led_dat->cdev.default_trigger = template->default_trigger;
98	led_dat->gpio = template->gpio;
99
100	led_dat->cdev.brightness_set = lt3593_led_set;
101
102	state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
103	led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;
104
105	if (!template->retain_state_suspended)
106		led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
107
108	ret = devm_gpio_request_one(parent, template->gpio, state ?
109				    GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW,
110				    template->name);
111	if (ret < 0)
112		return ret;
113
114	INIT_WORK(&led_dat->work, lt3593_led_work);
115
116	ret = led_classdev_register(parent, &led_dat->cdev);
117	if (ret < 0)
118		return ret;
119
120	dev_info(parent, "%s: registered LT3593 LED '%s' at GPIO %d\n",
121		KBUILD_MODNAME, template->name, template->gpio);
122
123	return 0;
124}
125
126static void delete_lt3593_led(struct lt3593_led_data *led)
127{
128	if (!gpio_is_valid(led->gpio))
129		return;
130
131	led_classdev_unregister(&led->cdev);
132	cancel_work_sync(&led->work);
133}
134
135static int lt3593_led_probe(struct platform_device *pdev)
136{
137	struct gpio_led_platform_data *pdata = dev_get_platdata(&pdev->dev);
138	struct lt3593_led_data *leds_data;
139	int i, ret = 0;
140
141	if (!pdata)
142		return -EBUSY;
143
144	leds_data = devm_kzalloc(&pdev->dev,
145			sizeof(struct lt3593_led_data) * pdata->num_leds,
146			GFP_KERNEL);
147	if (!leds_data)
148		return -ENOMEM;
149
150	for (i = 0; i < pdata->num_leds; i++) {
151		ret = create_lt3593_led(&pdata->leds[i], &leds_data[i],
152				      &pdev->dev);
153		if (ret < 0)
154			goto err;
155	}
156
157	platform_set_drvdata(pdev, leds_data);
158
159	return 0;
160
161err:
162	for (i = i - 1; i >= 0; i--)
163		delete_lt3593_led(&leds_data[i]);
164
165	return ret;
166}
167
168static int lt3593_led_remove(struct platform_device *pdev)
169{
170	int i;
171	struct gpio_led_platform_data *pdata = dev_get_platdata(&pdev->dev);
172	struct lt3593_led_data *leds_data;
173
174	leds_data = platform_get_drvdata(pdev);
175
176	for (i = 0; i < pdata->num_leds; i++)
177		delete_lt3593_led(&leds_data[i]);
178
179	return 0;
180}
181
182static struct platform_driver lt3593_led_driver = {
183	.probe		= lt3593_led_probe,
184	.remove		= lt3593_led_remove,
185	.driver		= {
186		.name	= "leds-lt3593",
187		.owner	= THIS_MODULE,
188	},
189};
190
191module_platform_driver(lt3593_led_driver);
192
193MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
194MODULE_DESCRIPTION("LED driver for LT3593 controllers");
195MODULE_LICENSE("GPL");
196MODULE_ALIAS("platform:leds-lt3593");
197