leds-lt3593.c revision a8dd18feb68ef0c5d3ec02f7d198740ddd7e8fd3 
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/init.h>
21#include <linux/platform_device.h>
22#include <linux/leds.h>
23#include <linux/workqueue.h>
24#include <linux/delay.h>
25#include <linux/gpio.h>
26
27struct lt3593_led_data {
28	struct led_classdev cdev;
29	unsigned gpio;
30	struct work_struct work;
31	u8 new_level;
32};
33
34static void lt3593_led_work(struct work_struct *work)
35{
36	int pulses;
37	struct lt3593_led_data *led_dat =
38		container_of(work, struct lt3593_led_data, work);
39
40	/*
41	 * The LT3593 resets its internal current level register to the maximum
42	 * level on the first falling edge on the control pin. Each following
43	 * falling edge decreases the current level by 625uA. Up to 32 pulses
44	 * can be sent, so the maximum power reduction is 20mA.
45	 * After a timeout of 128us, the value is taken from the register and
46	 * applied is to the output driver.
47	 */
48
49	if (led_dat->new_level == 0) {
50		gpio_set_value_cansleep(led_dat->gpio, 0);
51		return;
52	}
53
54	pulses = 32 - (led_dat->new_level * 32) / 255;
55
56	if (pulses == 0) {
57		gpio_set_value_cansleep(led_dat->gpio, 0);
58		mdelay(1);
59		gpio_set_value_cansleep(led_dat->gpio, 1);
60		return;
61	}
62
63	gpio_set_value_cansleep(led_dat->gpio, 1);
64
65	while (pulses--) {
66		gpio_set_value_cansleep(led_dat->gpio, 0);
67		udelay(1);
68		gpio_set_value_cansleep(led_dat->gpio, 1);
69		udelay(1);
70	}
71}
72
73static void lt3593_led_set(struct led_classdev *led_cdev,
74	enum led_brightness value)
75{
76	struct lt3593_led_data *led_dat =
77		container_of(led_cdev, struct lt3593_led_data, cdev);
78
79	led_dat->new_level = value;
80	schedule_work(&led_dat->work);
81}
82
83static int __devinit create_lt3593_led(const struct gpio_led *template,
84	struct lt3593_led_data *led_dat, struct device *parent)
85{
86	int ret, state;
87
88	/* skip leds on GPIOs that aren't available */
89	if (!gpio_is_valid(template->gpio)) {
90		printk(KERN_INFO "%s: skipping unavailable LT3593 LED at gpio %d (%s)\n",
91				KBUILD_MODNAME, template->gpio, template->name);
92		return 0;
93	}
94
95	ret = gpio_request(template->gpio, template->name);
96	if (ret < 0)
97		return ret;
98
99	led_dat->cdev.name = template->name;
100	led_dat->cdev.default_trigger = template->default_trigger;
101	led_dat->gpio = template->gpio;
102
103	led_dat->cdev.brightness_set = lt3593_led_set;
104
105	state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
106	led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;
107
108	if (!template->retain_state_suspended)
109		led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
110
111	ret = gpio_direction_output(led_dat->gpio, state);
112	if (ret < 0)
113		goto err;
114
115	INIT_WORK(&led_dat->work, lt3593_led_work);
116
117	ret = led_classdev_register(parent, &led_dat->cdev);
118	if (ret < 0)
119		goto err;
120
121	printk(KERN_INFO "%s: registered LT3593 LED '%s' at GPIO %d\n",
122		KBUILD_MODNAME, template->name, template->gpio);
123
124	return 0;
125
126err:
127	gpio_free(led_dat->gpio);
128	return ret;
129}
130
131static void delete_lt3593_led(struct lt3593_led_data *led)
132{
133	if (!gpio_is_valid(led->gpio))
134		return;
135
136	led_classdev_unregister(&led->cdev);
137	cancel_work_sync(&led->work);
138	gpio_free(led->gpio);
139}
140
141static int __devinit lt3593_led_probe(struct platform_device *pdev)
142{
143	struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
144	struct lt3593_led_data *leds_data;
145	int i, ret = 0;
146
147	if (!pdata)
148		return -EBUSY;
149
150	leds_data = kzalloc(sizeof(struct lt3593_led_data) * pdata->num_leds,
151				GFP_KERNEL);
152	if (!leds_data)
153		return -ENOMEM;
154
155	for (i = 0; i < pdata->num_leds; i++) {
156		ret = create_lt3593_led(&pdata->leds[i], &leds_data[i],
157				      &pdev->dev);
158		if (ret < 0)
159			goto err;
160	}
161
162	platform_set_drvdata(pdev, leds_data);
163
164	return 0;
165
166err:
167	for (i = i - 1; i >= 0; i--)
168		delete_lt3593_led(&leds_data[i]);
169
170	kfree(leds_data);
171
172	return ret;
173}
174
175static int __devexit lt3593_led_remove(struct platform_device *pdev)
176{
177	int i;
178	struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
179	struct lt3593_led_data *leds_data;
180
181	leds_data = platform_get_drvdata(pdev);
182
183	for (i = 0; i < pdata->num_leds; i++)
184		delete_lt3593_led(&leds_data[i]);
185
186	kfree(leds_data);
187
188	return 0;
189}
190
191static struct platform_driver lt3593_led_driver = {
192	.probe		= lt3593_led_probe,
193	.remove		= __devexit_p(lt3593_led_remove),
194	.driver		= {
195		.name	= "leds-lt3593",
196		.owner	= THIS_MODULE,
197	},
198};
199
200MODULE_ALIAS("platform:leds-lt3593");
201
202static int __init lt3593_led_init(void)
203{
204	return platform_driver_register(&lt3593_led_driver);
205}
206
207static void __exit lt3593_led_exit(void)
208{
209	platform_driver_unregister(&lt3593_led_driver);
210}
211
212module_init(lt3593_led_init);
213module_exit(lt3593_led_exit);
214
215MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
216MODULE_DESCRIPTION("LED driver for LT3593 controllers");
217MODULE_LICENSE("GPL");
218