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         /*
  57          * Disabling a PWM doesn't guarantee that it emits the inactive level.
  58          * So keep it on. Only for suspending the PWM should be disabled because
  59          * otherwise it refuses to suspend. The possible downside is that the
  60          * LED might stay (or even go) on.
  61          */
  62         led_dat->pwmstate.enabled = !(led_cdev->flags & LED_SUSPENDED);
  63         return pwm_apply_might_sleep(led_dat->pwm, &led_dat->pwmstate);
  64 }
  65
  66 __attribute__((nonnull))
  67 static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
  68                        struct led_pwm *led, struct fwnode_handle *fwnode)
  69 {
  70         struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
  71         struct led_init_data init_data = { .fwnode = fwnode };
  72         int ret;
  73
  74         led_data->active_low = led->active_low;
  75         led_data->cdev.name = led->name;
  76         led_data->cdev.brightness = LED_OFF;
  77         led_data->cdev.max_brightness = led->max_brightness;
  78         led_data->cdev.flags = LED_CORE_SUSPENDRESUME;
  79
  80         led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, NULL);
  81         if (IS_ERR(led_data->pwm))
  82                 return dev_err_probe(dev, PTR_ERR(led_data->pwm),
  83                                      "unable to request PWM for %s\n",
  84                                      led->name);
  85
  86         led_data->cdev.brightness_set_blocking = led_pwm_set;
  87
  88         /* init PWM state */
  89         switch (led->default_state) {
  90         case LEDS_DEFSTATE_KEEP:
  91                 pwm_get_state(led_data->pwm, &led_data->pwmstate);
  92                 if (led_data->pwmstate.period)
  93                         break;
  94                 led->default_state = LEDS_DEFSTATE_OFF;
  95                 dev_warn(dev,
  96                         "failed to read period for %s, default to off",
  97                         led->name);
  98                 fallthrough;
  99         default:
 100                 pwm_init_state(led_data->pwm, &led_data->pwmstate);
 101                 break;
 102         }
 103
 104         /* set brightness */
 105         switch (led->default_state) {
 106         case LEDS_DEFSTATE_ON:
 107                 led_data->cdev.brightness = led->max_brightness;
 108                 break;
 109         case LEDS_DEFSTATE_KEEP:
 110                 {
 111                 uint64_t brightness;
 112
 113                 brightness = led->max_brightness;
 114                 brightness *= led_data->pwmstate.duty_cycle;
 115                 do_div(brightness, led_data->pwmstate.period);
 116                 led_data->cdev.brightness = brightness;
 117                 }
 118                 break;
 119         }
 120
 121         ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
 122         if (ret) {
 123                 dev_err(dev, "failed to register PWM led for %s: %d\n",
 124                         led->name, ret);
 125                 return ret;
 126         }
 127
 128         if (led->default_state != LEDS_DEFSTATE_KEEP) {
 129                 ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
 130                 if (ret) {
 131                         dev_err(dev, "failed to set led PWM value for %s: %d",
 132                                 led->name, ret);
 133                         return ret;
 134                 }
 135         }
 136
 137         priv->num_leds++;
 138         return 0;
 139 }
 140
 141 static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
 142 {
 143         struct fwnode_handle *fwnode;
 144         struct led_pwm led;
 145         int ret;
 146
 147         device_for_each_child_node(dev, fwnode) {
 148                 memset(&led, 0, sizeof(led));
 149
 150                 ret = fwnode_property_read_string(fwnode, "label", &led.name);
 151                 if (ret && is_of_node(fwnode))
 152                         led.name = to_of_node(fwnode)->name;
 153
 154                 if (!led.name) {
 155                         ret = -EINVAL;
 156                         goto err_child_out;
 157                 }
 158
 159                 led.active_low = fwnode_property_read_bool(fwnode,
 160                                                            "active-low");
 161                 fwnode_property_read_u32(fwnode, "max-brightness",
 162                                          &led.max_brightness);
 163
 164                 led.default_state = led_init_default_state_get(fwnode);
 165
 166                 ret = led_pwm_add(dev, priv, &led, fwnode);
 167                 if (ret)
 168                         goto err_child_out;
 169         }
 170
 171         return 0;
 172
 173 err_child_out:
 174         fwnode_handle_put(fwnode);
 175         return ret;
 176 }
 177
 178 static int led_pwm_probe(struct platform_device *pdev)
 179 {
 180         struct led_pwm_priv *priv;
 181         int ret = 0;
 182         int count;
 183
 184         count = device_get_child_node_count(&pdev->dev);
 185
 186         if (!count)
 187                 return -EINVAL;
 188
 189         priv = devm_kzalloc(&pdev->dev, struct_size(priv, leds, count),
 190                             GFP_KERNEL);
 191         if (!priv)
 192                 return -ENOMEM;
 193
 194         ret = led_pwm_create_fwnode(&pdev->dev, priv);
 195
 196         if (ret)
 197                 return ret;
 198
 199         platform_set_drvdata(pdev, priv);
 200
 201         return 0;
 202 }
 203
 204 static const struct of_device_id of_pwm_leds_match[] = {
 205         { .compatible = "pwm-leds", },
 206         {},
 207 };
 208 MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
 209
 210 static struct platform_driver led_pwm_driver = {
 211         .probe          = led_pwm_probe,
 212         .driver         = {
 213                 .name   = "leds_pwm",
 214                 .of_match_table = of_pwm_leds_match,
 215         },
 216 };
 217
 218 module_platform_driver(led_pwm_driver);
 219
 220 MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>");
 221 MODULE_DESCRIPTION("generic PWM LED driver");
 222 MODULE_LICENSE("GPL v2");
 223 MODULE_ALIAS("platform:leds-pwm");