drivers/leds/leds-pwm.c

   1 /*
   2  * linux/drivers/leds-pwm.c
   3  *
   4  * simple PWM based LED control
   5  *
   6  * Copyright 2009 Luotao Fu @ Pengutronix (l.fu@pengutronix.de)
   7  *
   8  * based on leds-gpio.c by Raphael Assenat <raph@8d.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/kernel.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/of_platform.h>
  19 #include <linux/fb.h>
  20 #include <linux/leds.h>
  21 #include <linux/err.h>
  22 #include <linux/pwm.h>
  23 #include <linux/leds_pwm.h>
  24 #include <linux/slab.h>
  25
  26 struct led_pwm_data {
  27         struct led_classdev     cdev;
  28         struct pwm_device       *pwm;
  29         unsigned int            active_low;
  30         unsigned int            period;
  31         int                     duty;
  32 };
  33
  34 struct led_pwm_priv {
  35         int num_leds;
  36         struct led_pwm_data leds[0];
  37 };
  38
  39 static void __led_pwm_set(struct led_pwm_data *led_dat)
  40 {
  41         int new_duty = led_dat->duty;
  42
  43         pwm_config(led_dat->pwm, new_duty, led_dat->period);
  44
  45         if (new_duty == 0)
  46                 pwm_disable(led_dat->pwm);
  47         else
  48                 pwm_enable(led_dat->pwm);
  49 }
  50
  51 static int led_pwm_set(struct led_classdev *led_cdev,
  52                        enum led_brightness brightness)
  53 {
  54         struct led_pwm_data *led_dat =
  55                 container_of(led_cdev, struct led_pwm_data, cdev);
  56         unsigned int max = led_dat->cdev.max_brightness;
  57         unsigned long long duty =  led_dat->period;
  58
  59         duty *= brightness;
  60         do_div(duty, max);
  61
  62         if (led_dat->active_low)
  63                 duty = led_dat->period - duty;
  64
  65         led_dat->duty = duty;
  66
  67         __led_pwm_set(led_dat);
  68
  69         return 0;
  70 }
  71
  72 static inline size_t sizeof_pwm_leds_priv(int num_leds)
  73 {
  74         return sizeof(struct led_pwm_priv) +
  75                       (sizeof(struct led_pwm_data) * num_leds);
  76 }
  77
  78 static void led_pwm_cleanup(struct led_pwm_priv *priv)
  79 {
  80         while (priv->num_leds--)
  81                 led_classdev_unregister(&priv->leds[priv->num_leds].cdev);
  82 }
  83
  84 static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
  85                        struct led_pwm *led, struct device_node *child)
  86 {
  87         struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
  88         struct pwm_args pargs;
  89         int ret;
  90
  91         led_data->active_low = led->active_low;
  92         led_data->cdev.name = led->name;
  93         led_data->cdev.default_trigger = led->default_trigger;
  94         led_data->cdev.brightness = LED_OFF;
  95         led_data->cdev.max_brightness = led->max_brightness;
  96         led_data->cdev.flags = LED_CORE_SUSPENDRESUME;
  97
  98         if (child)
  99                 led_data->pwm = devm_of_pwm_get(dev, child, NULL);
 100         else
 101                 led_data->pwm = devm_pwm_get(dev, led->name);
 102         if (IS_ERR(led_data->pwm)) {
 103                 ret = PTR_ERR(led_data->pwm);
 104                 dev_err(dev, "unable to request PWM for %s: %d\n",
 105                         led->name, ret);
 106                 return ret;
 107         }
 108
 109         led_data->cdev.brightness_set_blocking = led_pwm_set;
 110
 111         /*
 112          * FIXME: pwm_apply_args() should be removed when switching to the
 113          * atomic PWM API.
 114          */
 115         pwm_apply_args(led_data->pwm);
 116
 117         pwm_get_args(led_data->pwm, &pargs);
 118
 119         led_data->period = pargs.period;
 120         if (!led_data->period && (led->pwm_period_ns > 0))
 121                 led_data->period = led->pwm_period_ns;
 122
 123         ret = led_classdev_register(dev, &led_data->cdev);
 124         if (ret == 0) {
 125                 priv->num_leds++;
 126                 led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
 127         } else {
 128                 dev_err(dev, "failed to register PWM led for %s: %d\n",
 129                         led->name, ret);
 130         }
 131
 132         return ret;
 133 }
 134
 135 static int led_pwm_create_of(struct device *dev, struct led_pwm_priv *priv)
 136 {
 137         struct device_node *child;
 138         struct led_pwm led;
 139         int ret = 0;
 140
 141         memset(&led, 0, sizeof(led));
 142
 143         for_each_child_of_node(dev->of_node, child) {
 144                 led.name = of_get_property(child, "label", NULL) ? :
 145                            child->name;
 146
 147                 led.default_trigger = of_get_property(child,
 148                                                 "linux,default-trigger", NULL);
 149                 led.active_low = of_property_read_bool(child, "active-low");
 150                 of_property_read_u32(child, "max-brightness",
 151                                      &led.max_brightness);
 152
 153                 ret = led_pwm_add(dev, priv, &led, child);
 154                 if (ret) {
 155                         of_node_put(child);
 156                         break;
 157                 }
 158         }
 159
 160         return ret;
 161 }
 162
 163 static int led_pwm_probe(struct platform_device *pdev)
 164 {
 165         struct led_pwm_platform_data *pdata = dev_get_platdata(&pdev->dev);
 166         struct led_pwm_priv *priv;
 167         int count, i;
 168         int ret = 0;
 169
 170         if (pdata)
 171                 count = pdata->num_leds;
 172         else
 173                 count = of_get_child_count(pdev->dev.of_node);
 174
 175         if (!count)
 176                 return -EINVAL;
 177
 178         priv = devm_kzalloc(&pdev->dev, sizeof_pwm_leds_priv(count),
 179                             GFP_KERNEL);
 180         if (!priv)
 181                 return -ENOMEM;
 182
 183         if (pdata) {
 184                 for (i = 0; i < count; i++) {
 185                         ret = led_pwm_add(&pdev->dev, priv, &pdata->leds[i],
 186                                           NULL);
 187                         if (ret)
 188                                 break;
 189                 }
 190         } else {
 191                 ret = led_pwm_create_of(&pdev->dev, priv);
 192         }
 193
 194         if (ret) {
 195                 led_pwm_cleanup(priv);
 196                 return ret;
 197         }
 198
 199         platform_set_drvdata(pdev, priv);
 200
 201         return 0;
 202 }
 203
 204 static int led_pwm_remove(struct platform_device *pdev)
 205 {
 206         struct led_pwm_priv *priv = platform_get_drvdata(pdev);
 207
 208         led_pwm_cleanup(priv);
 209
 210         return 0;
 211 }
 212
 213 static const struct of_device_id of_pwm_leds_match[] = {
 214         { .compatible = "pwm-leds", },
 215         {},
 216 };
 217 MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
 218
 219 static struct platform_driver led_pwm_driver = {
 220         .probe          = led_pwm_probe,
 221         .remove         = led_pwm_remove,
 222         .driver         = {
 223                 .name   = "leds_pwm",
 224                 .of_match_table = of_pwm_leds_match,
 225         },
 226 };
 227
 228 module_platform_driver(led_pwm_driver);
 229
 230 MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>");
 231 MODULE_DESCRIPTION("generic PWM LED driver");
 232 MODULE_LICENSE("GPL v2");
 233 MODULE_ALIAS("platform:leds-pwm");