linux/drivers/leds/leds-lt3593.c
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   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 = devm_kzalloc(&pdev->dev,
 153                        sizeof(struct lt3593_led_data) * pdata->num_leds,
 154                        GFP_KERNEL);
 155        if (!leds_data)
 156                return -ENOMEM;
 157
 158        for (i = 0; i < pdata->num_leds; i++) {
 159                ret = create_lt3593_led(&pdata->leds[i], &leds_data[i],
 160                                      &pdev->dev);
 161                if (ret < 0)
 162                        goto err;
 163        }
 164
 165        platform_set_drvdata(pdev, leds_data);
 166
 167        return 0;
 168
 169err:
 170        for (i = i - 1; i >= 0; i--)
 171                delete_lt3593_led(&leds_data[i]);
 172
 173        return ret;
 174}
 175
 176static int __devexit lt3593_led_remove(struct platform_device *pdev)
 177{
 178        int i;
 179        struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
 180        struct lt3593_led_data *leds_data;
 181
 182        leds_data = platform_get_drvdata(pdev);
 183
 184        for (i = 0; i < pdata->num_leds; i++)
 185                delete_lt3593_led(&leds_data[i]);
 186
 187        return 0;
 188}
 189
 190static struct platform_driver lt3593_led_driver = {
 191        .probe          = lt3593_led_probe,
 192        .remove         = __devexit_p(lt3593_led_remove),
 193        .driver         = {
 194                .name   = "leds-lt3593",
 195                .owner  = THIS_MODULE,
 196        },
 197};
 198
 199module_platform_driver(lt3593_led_driver);
 200
 201MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
 202MODULE_DESCRIPTION("LED driver for LT3593 controllers");
 203MODULE_LICENSE("GPL");
 204MODULE_ALIAS("platform:leds-lt3593");
 205
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