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 fwnode_handle *fwnode)
  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 (fwnode)
  92                 led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, 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, to_of_node(fwnode),
 118                                             &led_data->cdev);
 119         if (ret == 0) {
 120                 priv->num_leds++;
 121                 led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
 122         } else {
 123                 dev_err(dev, "failed to register PWM led for %s: %d\n",
 124                         led->name, ret);
 125         }
 126
 127         return ret;
 128 }
 129
 130 static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
 131 {
 132         struct fwnode_handle *fwnode;
 133         struct led_pwm led;
 134         int ret = 0;
 135
 136         memset(&led, 0, sizeof(led));
 137
 138         device_for_each_child_node(dev, fwnode) {
 139                 ret = fwnode_property_read_string(fwnode, "label", &led.name);
 140                 if (ret && is_of_node(fwnode))
 141                         led.name = to_of_node(fwnode)->name;
 142
 143                 if (!led.name) {
 144                         fwnode_handle_put(fwnode);
 145                         return -EINVAL;
 146                 }
 147
 148                 fwnode_property_read_string(fwnode, "linux,default-trigger",
 149                                             &led.default_trigger);
 150
 151                 led.active_low = fwnode_property_read_bool(fwnode,
 152                                                            "active-low");
 153                 fwnode_property_read_u32(fwnode, "max-brightness",
 154                                          &led.max_brightness);
 155
 156                 ret = led_pwm_add(dev, priv, &led, fwnode);
 157                 if (ret) {
 158                         fwnode_handle_put(fwnode);
 159                         break;
 160                 }
 161         }
 162
 163         return ret;
 164 }
 165
 166 static int led_pwm_probe(struct platform_device *pdev)
 167 {
 168         struct led_pwm_platform_data *pdata = dev_get_platdata(&pdev->dev);
 169         struct led_pwm_priv *priv;
 170         int count, i;
 171         int ret = 0;
 172
 173         if (pdata)
 174                 count = pdata->num_leds;
 175         else
 176                 count = device_get_child_node_count(&pdev->dev);
 177
 178         if (!count)
 179                 return -EINVAL;
 180
 181         priv = devm_kzalloc(&pdev->dev, sizeof_pwm_leds_priv(count),
 182                             GFP_KERNEL);
 183         if (!priv)
 184                 return -ENOMEM;
 185
 186         if (pdata) {
 187                 for (i = 0; i < count; i++) {
 188                         ret = led_pwm_add(&pdev->dev, priv, &pdata->leds[i],
 189                                           NULL);
 190                         if (ret)
 191                                 break;
 192                 }
 193         } else {
 194                 ret = led_pwm_create_fwnode(&pdev->dev, priv);
 195         }
 196
 197         if (ret)
 198                 return ret;
 199
 200         platform_set_drvdata(pdev, priv);
 201
 202         return 0;
 203 }
 204
 205 static const struct of_device_id of_pwm_leds_match[] = {
 206         { .compatible = "pwm-leds", },
 207         {},
 208 };
 209 MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
 210
 211 static struct platform_driver led_pwm_driver = {
 212         .probe          = led_pwm_probe,
 213         .driver         = {
 214                 .name   = "leds_pwm",
 215                 .of_match_table = of_pwm_leds_match,
 216         },
 217 };
 218
 219 module_platform_driver(led_pwm_driver);
 220
 221 MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>");
 222 MODULE_DESCRIPTION("generic PWM LED driver");
 223 MODULE_LICENSE("GPL v2");
 224 MODULE_ALIAS("platform:leds-pwm");