drivers/leds/leds-pwm.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/drivers/leds-pwm.c
   4  *
   5  * simple PWM based LED control
   6  *
   7  * Copyright 2009 Luotao Fu @ Pengutronix (l.fu@pengutronix.de)
   8  *
   9  * based on leds-gpio.c by Raphael Assenat <raph@8d.com>
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/kernel.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/of_platform.h>
  16 #include <linux/leds.h>
  17 #include <linux/err.h>
  18 #include <linux/pwm.h>
  19 #include <linux/slab.h>
  20
  21 struct led_pwm {
  22         const char      *name;
  23         u8              active_low;
  24         unsigned int    max_brightness;
  25 };
  26
  27 struct led_pwm_data {
  28         struct led_classdev     cdev;
  29         struct pwm_device       *pwm;
  30         struct pwm_state        pwmstate;
  31         unsigned int            active_low;
  32 };
  33
  34 struct led_pwm_priv {
  35         int num_leds;
  36         struct led_pwm_data leds[];
  37 };
  38
  39 static int led_pwm_set(struct led_classdev *led_cdev,
  40                        enum led_brightness brightness)
  41 {
  42         struct led_pwm_data *led_dat =
  43                 container_of(led_cdev, struct led_pwm_data, cdev);
  44         unsigned int max = led_dat->cdev.max_brightness;
  45         unsigned long long duty = led_dat->pwmstate.period;
  46
  47         duty *= brightness;
  48         do_div(duty, max);
  49
  50         if (led_dat->active_low)
  51                 duty = led_dat->pwmstate.period - duty;
  52
  53         led_dat->pwmstate.duty_cycle = duty;
  54         led_dat->pwmstate.enabled = duty > 0;
  55         return pwm_apply_state(led_dat->pwm, &led_dat->pwmstate);
  56 }
  57
  58 __attribute__((nonnull))
  59 static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
  60                        struct led_pwm *led, struct fwnode_handle *fwnode)
  61 {
  62         struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
  63         struct led_init_data init_data = { .fwnode = fwnode };
  64         int ret;
  65
  66         led_data->active_low = led->active_low;
  67         led_data->cdev.name = led->name;
  68         led_data->cdev.brightness = LED_OFF;
  69         led_data->cdev.max_brightness = led->max_brightness;
  70         led_data->cdev.flags = LED_CORE_SUSPENDRESUME;
  71
  72         led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, NULL);
  73         if (IS_ERR(led_data->pwm))
  74                 return dev_err_probe(dev, PTR_ERR(led_data->pwm),
  75                                      "unable to request PWM for %s\n",
  76                                      led->name);
  77
  78         led_data->cdev.brightness_set_blocking = led_pwm_set;
  79
  80         pwm_init_state(led_data->pwm, &led_data->pwmstate);
  81
  82         ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
  83         if (ret) {
  84                 dev_err(dev, "failed to register PWM led for %s: %d\n",
  85                         led->name, ret);
  86                 return ret;
  87         }
  88
  89         ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
  90         if (ret) {
  91                 dev_err(dev, "failed to set led PWM value for %s: %d",
  92                         led->name, ret);
  93                 return ret;
  94         }
  95
  96         priv->num_leds++;
  97         return 0;
  98 }
  99
 100 static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
 101 {
 102         struct fwnode_handle *fwnode;
 103         struct led_pwm led;
 104         int ret = 0;
 105
 106         memset(&led, 0, sizeof(led));
 107
 108         device_for_each_child_node(dev, fwnode) {
 109                 ret = fwnode_property_read_string(fwnode, "label", &led.name);
 110                 if (ret && is_of_node(fwnode))
 111                         led.name = to_of_node(fwnode)->name;
 112
 113                 if (!led.name) {
 114                         fwnode_handle_put(fwnode);
 115                         return -EINVAL;
 116                 }
 117
 118                 led.active_low = fwnode_property_read_bool(fwnode,
 119                                                            "active-low");
 120                 fwnode_property_read_u32(fwnode, "max-brightness",
 121                                          &led.max_brightness);
 122
 123                 ret = led_pwm_add(dev, priv, &led, fwnode);
 124                 if (ret) {
 125                         fwnode_handle_put(fwnode);
 126                         break;
 127                 }
 128         }
 129
 130         return ret;
 131 }
 132
 133 static int led_pwm_probe(struct platform_device *pdev)
 134 {
 135         struct led_pwm_priv *priv;
 136         int ret = 0;
 137         int count;
 138
 139         count = device_get_child_node_count(&pdev->dev);
 140
 141         if (!count)
 142                 return -EINVAL;
 143
 144         priv = devm_kzalloc(&pdev->dev, struct_size(priv, leds, count),
 145                             GFP_KERNEL);
 146         if (!priv)
 147                 return -ENOMEM;
 148
 149         ret = led_pwm_create_fwnode(&pdev->dev, priv);
 150
 151         if (ret)
 152                 return ret;
 153
 154         platform_set_drvdata(pdev, priv);
 155
 156         return 0;
 157 }
 158
 159 static const struct of_device_id of_pwm_leds_match[] = {
 160         { .compatible = "pwm-leds", },
 161         {},
 162 };
 163 MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
 164
 165 static struct platform_driver led_pwm_driver = {
 166         .probe          = led_pwm_probe,
 167         .driver         = {
 168                 .name   = "leds_pwm",
 169                 .of_match_table = of_pwm_leds_match,
 170         },
 171 };
 172
 173 module_platform_driver(led_pwm_driver);
 174
 175 MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>");
 176 MODULE_DESCRIPTION("generic PWM LED driver");
 177 MODULE_LICENSE("GPL v2");
 178 MODULE_ALIAS("platform:leds-pwm");