leds-lt3593.c revision 54f4dedb5368fff81b722b551e2f15a75175d7b7 
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#include <linux/slab.h>
27#include <linux/module.h>
28
29struct lt3593_led_data {
30	struct led_classdev cdev;
31	unsigned gpio;
32	struct work_struct work;
33	u8 new_level;
34};
35
36static void lt3593_led_work(struct work_struct *work)
37{
38	int pulses;
39	struct lt3593_led_data *led_dat =
40		container_of(work, struct lt3593_led_data, work);
41
42	/*
43	 * The LT3593 resets its internal current level register to the maximum
44	 * level on the first falling edge on the control pin. Each following
45	 * falling edge decreases the current level by 625uA. Up to 32 pulses
46	 * can be sent, so the maximum power reduction is 20mA.
47	 * After a timeout of 128us, the value is taken from the register and
48	 * applied is to the output driver.
49	 */
50
51	if (led_dat->new_level == 0) {
52		gpio_set_value_cansleep(led_dat->gpio, 0);
53		return;
54	}
55
56	pulses = 32 - (led_dat->new_level * 32) / 255;
57
58	if (pulses == 0) {
59		gpio_set_value_cansleep(led_dat->gpio, 0);
60		mdelay(1);
61		gpio_set_value_cansleep(led_dat->gpio, 1);
62		return;
63	}
64
65	gpio_set_value_cansleep(led_dat->gpio, 1);
66
67	while (pulses--) {
68		gpio_set_value_cansleep(led_dat->gpio, 0);
69		udelay(1);
70		gpio_set_value_cansleep(led_dat->gpio, 1);
71		udelay(1);
72	}
73}
74
75static void lt3593_led_set(struct led_classdev *led_cdev,
76	enum led_brightness value)
77{
78	struct lt3593_led_data *led_dat =
79		container_of(led_cdev, struct lt3593_led_data, cdev);
80
81	led_dat->new_level = value;
82	schedule_work(&led_dat->work);
83}
84
85static int __devinit create_lt3593_led(const struct gpio_led *template,
86	struct lt3593_led_data *led_dat, struct device *parent)
87{
88	int ret, state;
89
90	/* skip leds on GPIOs that aren't available */
91	if (!gpio_is_valid(template->gpio)) {
92		printk(KERN_INFO "%s: skipping unavailable LT3593 LED at gpio %d (%s)\n",
93				KBUILD_MODNAME, template->gpio, template->name);
94		return 0;
95	}
96
97	ret = gpio_request(template->gpio, template->name);
98	if (ret < 0)
99		return ret;
100
101	led_dat->cdev.name = template->name;
102	led_dat->cdev.default_trigger = template->default_trigger;
103	led_dat->gpio = template->gpio;
104
105	led_dat->cdev.brightness_set = lt3593_led_set;
106
107	state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
108	led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;
109
110	if (!template->retain_state_suspended)
111		led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
112
113	ret = gpio_direction_output(led_dat->gpio, state);
114	if (ret < 0)
115		goto err;
116
117	INIT_WORK(&led_dat->work, lt3593_led_work);
118
119	ret = led_classdev_register(parent, &led_dat->cdev);
120	if (ret < 0)
121		goto err;
122
123	printk(KERN_INFO "%s: registered LT3593 LED '%s' at GPIO %d\n",
124		KBUILD_MODNAME, template->name, template->gpio);
125
126	return 0;
127
128err:
129	gpio_free(led_dat->gpio);
130	return ret;
131}
132
133static void delete_lt3593_led(struct lt3593_led_data *led)
134{
135	if (!gpio_is_valid(led->gpio))
136		return;
137
138	led_classdev_unregister(&led->cdev);
139	cancel_work_sync(&led->work);
140	gpio_free(led->gpio);
141}
142
143static int __devinit lt3593_led_probe(struct platform_device *pdev)
144{
145	struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
146	struct lt3593_led_data *leds_data;
147	int i, ret = 0;
148
149	if (!pdata)
150		return -EBUSY;
151
152	leds_data = kzalloc(sizeof(struct lt3593_led_data) * pdata->num_leds,
153				GFP_KERNEL);
154	if (!leds_data)
155		return -ENOMEM;
156
157	for (i = 0; i < pdata->num_leds; i++) {
158		ret = create_lt3593_led(&pdata->leds[i], &leds_data[i],
159				      &pdev->dev);
160		if (ret < 0)
161			goto err;
162	}
163
164	platform_set_drvdata(pdev, leds_data);
165
166	return 0;
167
168err:
169	for (i = i - 1; i >= 0; i--)
170		delete_lt3593_led(&leds_data[i]);
171
172	kfree(leds_data);
173
174	return ret;
175}
176
177static int __devexit lt3593_led_remove(struct platform_device *pdev)
178{
179	int i;
180	struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
181	struct lt3593_led_data *leds_data;
182
183	leds_data = platform_get_drvdata(pdev);
184
185	for (i = 0; i < pdata->num_leds; i++)
186		delete_lt3593_led(&leds_data[i]);
187
188	kfree(leds_data);
189
190	return 0;
191}
192
193static struct platform_driver lt3593_led_driver = {
194	.probe		= lt3593_led_probe,
195	.remove		= __devexit_p(lt3593_led_remove),
196	.driver		= {
197		.name	= "leds-lt3593",
198		.owner	= THIS_MODULE,
199	},
200};
201
202MODULE_ALIAS("platform:leds-lt3593");
203
204static int __init lt3593_led_init(void)
205{
206	return platform_driver_register(&lt3593_led_driver);
207}
208
209static void __exit lt3593_led_exit(void)
210{
211	platform_driver_unregister(&lt3593_led_driver);
212}
213
214module_init(lt3593_led_init);
215module_exit(lt3593_led_exit);
216
217MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
218MODULE_DESCRIPTION("LED driver for LT3593 controllers");
219MODULE_LICENSE("GPL");
220