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 ([email protected])
   8  *
   9  * based on leds-gpio.c by Raphael Assenat <[email protected]>
  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
  21 struct led_pwm {
  22         const char      *name;
  23         u8              active_low;
  24         u8              default_state;
  25         unsigned int    max_brightness;
  26 };
  27
  28 struct led_pwm_data {
  29         struct led_classdev     cdev;
  30         struct pwm_device       *pwm;
  31         struct pwm_state        pwmstate;
  32         unsigned int            active_low;
  33 };
  34
  35 struct led_pwm_priv {
  36         int num_leds;
  37         struct led_pwm_data leds[];
  38 };
  39
  40 static int led_pwm_set(struct led_classdev *led_cdev,
  41                        enum led_brightness brightness)
  42 {
  43         struct led_pwm_data *led_dat =
  44                 container_of(led_cdev, struct led_pwm_data, cdev);
  45         unsigned int max = led_dat->cdev.max_brightness;
  46         unsigned long long duty = led_dat->pwmstate.period;
  47
  48         duty *= brightness;
  49         do_div(duty, max);
  50
  51         if (led_dat->active_low)
  52                 duty = led_dat->pwmstate.period - duty;
  53
  54         led_dat->pwmstate.duty_cycle = duty;
  55         /*
  56          * Disabling a PWM doesn't guarantee that it emits the inactive level.
  57          * So keep it on. Only for suspending the PWM should be disabled because
  58          * otherwise it refuses to suspend. The possible downside is that the
  59          * LED might stay (or even go) on.
  60          */
  61         led_dat->pwmstate.enabled = !(led_cdev->flags & LED_SUSPENDED);
  62         return pwm_apply_might_sleep(led_dat->pwm, &led_dat->pwmstate);
  63 }
  64
  65 static int led_pwm_default_brightness_get(struct fwnode_handle *fwnode,
  66                                           int max_brightness)
  67 {
  68         unsigned int default_brightness;
  69         int ret;
  70
  71         ret = fwnode_property_read_u32(fwnode, "default-brightness",
  72                                        &default_brightness);
  73         if (ret < 0 || default_brightness > max_brightness)
  74                 default_brightness = max_brightness;
  75
  76         return default_brightness;
  77 }
  78
  79 __attribute__((nonnull))
  80 static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
  81                        struct led_pwm *led, struct fwnode_handle *fwnode)
  82 {
  83         struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
  84         struct led_init_data init_data = { .fwnode = fwnode };
  85         int ret;
  86
  87         led_data->active_low = led->active_low;
  88         led_data->cdev.name = led->name;
  89         led_data->cdev.brightness = LED_OFF;
  90         led_data->cdev.max_brightness = led->max_brightness;
  91         led_data->cdev.flags = LED_CORE_SUSPENDRESUME;
  92
  93         led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, NULL);
  94         if (IS_ERR(led_data->pwm))
  95                 return dev_err_probe(dev, PTR_ERR(led_data->pwm),
  96                                      "unable to request PWM for %s\n",
  97                                      led->name);
  98
  99         led_data->cdev.brightness_set_blocking = led_pwm_set;
 100
 101         /* init PWM state */
 102         switch (led->default_state) {
 103         case LEDS_DEFSTATE_KEEP:
 104                 pwm_get_state(led_data->pwm, &led_data->pwmstate);
 105                 if (led_data->pwmstate.period)
 106                         break;
 107                 led->default_state = LEDS_DEFSTATE_OFF;
 108                 dev_warn(dev,
 109                         "failed to read period for %s, default to off",
 110                         led->name);
 111                 fallthrough;
 112         default:
 113                 pwm_init_state(led_data->pwm, &led_data->pwmstate);
 114                 break;
 115         }
 116
 117         /* set brightness */
 118         switch (led->default_state) {
 119         case LEDS_DEFSTATE_ON:
 120                 led_data->cdev.brightness =
 121                         led_pwm_default_brightness_get(fwnode, led->max_brightness);
 122                 break;
 123         case LEDS_DEFSTATE_KEEP:
 124                 {
 125                 uint64_t brightness;
 126
 127                 brightness = led->max_brightness;
 128                 brightness *= led_data->pwmstate.duty_cycle;
 129                 do_div(brightness, led_data->pwmstate.period);
 130                 led_data->cdev.brightness = brightness;
 131                 }
 132                 break;
 133         }
 134
 135         ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
 136         if (ret) {
 137                 dev_err(dev, "failed to register PWM led for %s: %d\n",
 138                         led->name, ret);
 139                 return ret;
 140         }
 141
 142         if (led->default_state != LEDS_DEFSTATE_KEEP) {
 143                 ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
 144                 if (ret) {
 145                         dev_err(dev, "failed to set led PWM value for %s: %d",
 146                                 led->name, ret);
 147                         return ret;
 148                 }
 149         }
 150
 151         priv->num_leds++;
 152         return 0;
 153 }
 154
 155 static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
 156 {
 157         struct led_pwm led;
 158         int ret;
 159
 160         device_for_each_child_node_scoped(dev, fwnode) {
 161                 memset(&led, 0, sizeof(led));
 162
 163                 ret = fwnode_property_read_string(fwnode, "label", &led.name);
 164                 if (ret && is_of_node(fwnode))
 165                         led.name = to_of_node(fwnode)->name;
 166
 167                 if (!led.name)
 168                         return -EINVAL;
 169
 170                 led.active_low = fwnode_property_read_bool(fwnode,
 171                                                            "active-low");
 172                 fwnode_property_read_u32(fwnode, "max-brightness",
 173                                          &led.max_brightness);
 174
 175                 led.default_state = led_init_default_state_get(fwnode);
 176
 177                 ret = led_pwm_add(dev, priv, &led, fwnode);
 178                 if (ret)
 179                         return ret;
 180         }
 181
 182         return 0;
 183 }
 184
 185 static int led_pwm_probe(struct platform_device *pdev)
 186 {
 187         struct led_pwm_priv *priv;
 188         int ret = 0;
 189         int count;
 190
 191         count = device_get_child_node_count(&pdev->dev);
 192
 193         if (!count)
 194                 return -EINVAL;
 195
 196         priv = devm_kzalloc(&pdev->dev, struct_size(priv, leds, count),
 197                             GFP_KERNEL);
 198         if (!priv)
 199                 return -ENOMEM;
 200
 201         ret = led_pwm_create_fwnode(&pdev->dev, priv);
 202
 203         if (ret)
 204                 return ret;
 205
 206         platform_set_drvdata(pdev, priv);
 207
 208         return 0;
 209 }
 210
 211 static const struct of_device_id of_pwm_leds_match[] = {
 212         { .compatible = "pwm-leds", },
 213         {},
 214 };
 215 MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
 216
 217 static struct platform_driver led_pwm_driver = {
 218         .probe          = led_pwm_probe,
 219         .driver         = {
 220                 .name   = "leds_pwm",
 221                 .of_match_table = of_pwm_leds_match,
 222         },
 223 };
 224
 225 module_platform_driver(led_pwm_driver);
 226
 227 MODULE_AUTHOR("Luotao Fu <[email protected]>");
 228 MODULE_DESCRIPTION("generic PWM LED driver");
 229 MODULE_LICENSE("GPL v2");
 230 MODULE_ALIAS("platform:leds-pwm");