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