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.h>
  16 #include <linux/leds.h>
  17 #include <linux/err.h>
  18 #include <linux/pwm.h>
  19 #include <linux/slab.h>
  20 #include "leds.h"
  21
  22 struct led_pwm {
  23         const char      *name;
  24         u8              active_low;
  25         u8              default_state;
  26         unsigned int    max_brightness;
  27 };
  28
  29 struct led_pwm_data {
  30         struct led_classdev     cdev;
  31         struct pwm_device       *pwm;
  32         struct pwm_state        pwmstate;
  33         unsigned int            active_low;
  34 };
  35
  36 struct led_pwm_priv {
  37         int num_leds;
  38         struct led_pwm_data leds[];
  39 };
  40
  41 static int led_pwm_set(struct led_classdev *led_cdev,
  42                        enum led_brightness brightness)
  43 {
  44         struct led_pwm_data *led_dat =
  45                 container_of(led_cdev, struct led_pwm_data, cdev);
  46         unsigned int max = led_dat->cdev.max_brightness;
  47         unsigned long long duty = led_dat->pwmstate.period;
  48
  49         duty *= brightness;
  50         do_div(duty, max);
  51
  52         if (led_dat->active_low)
  53                 duty = led_dat->pwmstate.period - duty;
  54
  55         led_dat->pwmstate.duty_cycle = duty;
  56         led_dat->pwmstate.enabled = true;
  57         return pwm_apply_state(led_dat->pwm, &led_dat->pwmstate);
  58 }
  59
  60 __attribute__((nonnull))
  61 static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
  62                        struct led_pwm *led, struct fwnode_handle *fwnode)
  63 {
  64         struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
  65         struct led_init_data init_data = { .fwnode = fwnode };
  66         int ret;
  67
  68         led_data->active_low = led->active_low;
  69         led_data->cdev.name = led->name;
  70         led_data->cdev.brightness = LED_OFF;
  71         led_data->cdev.max_brightness = led->max_brightness;
  72         led_data->cdev.flags = LED_CORE_SUSPENDRESUME;
  73
  74         led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, NULL);
  75         if (IS_ERR(led_data->pwm))
  76                 return dev_err_probe(dev, PTR_ERR(led_data->pwm),
  77                                      "unable to request PWM for %s\n",
  78                                      led->name);
  79
  80         led_data->cdev.brightness_set_blocking = led_pwm_set;
  81
  82         /* init PWM state */
  83         switch (led->default_state) {
  84         case LEDS_DEFSTATE_KEEP:
  85                 pwm_get_state(led_data->pwm, &led_data->pwmstate);
  86                 if (led_data->pwmstate.period)
  87                         break;
  88                 led->default_state = LEDS_DEFSTATE_OFF;
  89                 dev_warn(dev,
  90                         "failed to read period for %s, default to off",
  91                         led->name);
  92                 fallthrough;
  93         default:
  94                 pwm_init_state(led_data->pwm, &led_data->pwmstate);
  95                 break;
  96         }
  97
  98         /* set brightness */
  99         switch (led->default_state) {
 100         case LEDS_DEFSTATE_ON:
 101                 led_data->cdev.brightness = led->max_brightness;
 102                 break;
 103         case LEDS_DEFSTATE_KEEP:
 104                 {
 105                 uint64_t brightness;
 106
 107                 brightness = led->max_brightness;
 108                 brightness *= led_data->pwmstate.duty_cycle;
 109                 do_div(brightness, led_data->pwmstate.period);
 110                 led_data->cdev.brightness = brightness;
 111                 }
 112                 break;
 113         }
 114
 115         ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
 116         if (ret) {
 117                 dev_err(dev, "failed to register PWM led for %s: %d\n",
 118                         led->name, ret);
 119                 return ret;
 120         }
 121
 122         if (led->default_state != LEDS_DEFSTATE_KEEP) {
 123                 ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
 124                 if (ret) {
 125                         dev_err(dev, "failed to set led PWM value for %s: %d",
 126                                 led->name, ret);
 127                         return ret;
 128                 }
 129         }
 130
 131         priv->num_leds++;
 132         return 0;
 133 }
 134
 135 static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
 136 {
 137         struct fwnode_handle *fwnode;
 138         struct led_pwm led;
 139         int ret;
 140
 141         device_for_each_child_node(dev, fwnode) {
 142                 memset(&led, 0, sizeof(led));
 143
 144                 ret = fwnode_property_read_string(fwnode, "label", &led.name);
 145                 if (ret && is_of_node(fwnode))
 146                         led.name = to_of_node(fwnode)->name;
 147
 148                 if (!led.name) {
 149                         ret = -EINVAL;
 150                         goto err_child_out;
 151                 }
 152
 153                 led.active_low = fwnode_property_read_bool(fwnode,
 154                                                            "active-low");
 155                 fwnode_property_read_u32(fwnode, "max-brightness",
 156                                          &led.max_brightness);
 157
 158                 led.default_state = led_init_default_state_get(fwnode);
 159
 160                 ret = led_pwm_add(dev, priv, &led, fwnode);
 161                 if (ret)
 162                         goto err_child_out;
 163         }
 164
 165         return 0;
 166
 167 err_child_out:
 168         fwnode_handle_put(fwnode);
 169         return ret;
 170 }
 171
 172 static int led_pwm_probe(struct platform_device *pdev)
 173 {
 174         struct led_pwm_priv *priv;
 175         int ret = 0;
 176         int count;
 177
 178         count = device_get_child_node_count(&pdev->dev);
 179
 180         if (!count)
 181                 return -EINVAL;
 182
 183         priv = devm_kzalloc(&pdev->dev, struct_size(priv, leds, count),
 184                             GFP_KERNEL);
 185         if (!priv)
 186                 return -ENOMEM;
 187
 188         ret = led_pwm_create_fwnode(&pdev->dev, priv);
 189
 190         if (ret)
 191                 return ret;
 192
 193         platform_set_drvdata(pdev, priv);
 194
 195         return 0;
 196 }
 197
 198 static const struct of_device_id of_pwm_leds_match[] = {
 199         { .compatible = "pwm-leds", },
 200         {},
 201 };
 202 MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
 203
 204 static struct platform_driver led_pwm_driver = {
 205         .probe          = led_pwm_probe,
 206         .driver         = {
 207                 .name   = "leds_pwm",
 208                 .of_match_table = of_pwm_leds_match,
 209         },
 210 };
 211
 212 module_platform_driver(led_pwm_driver);
 213
 214 MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>");
 215 MODULE_DESCRIPTION("generic PWM LED driver");
 216 MODULE_LICENSE("GPL v2");
 217 MODULE_ALIAS("platform:leds-pwm");