drivers/leds/leds-pwm.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * linux/drivers/leds-pwm.c
0004  *
0005  * simple PWM based LED control
0006  *
0007  * Copyright 2009 Luotao Fu @ Pengutronix (l.fu@pengutronix.de)
0008  *
0009  * based on leds-gpio.c by Raphael Assenat <raph@8d.com>
0010  */
0011
0012 #include <linux/module.h>
0013 #include <linux/kernel.h>
0014 #include <linux/platform_device.h>
0015 #include <linux/of_platform.h>
0016 #include <linux/leds.h>
0017 #include <linux/err.h>
0018 #include <linux/pwm.h>
0019 #include <linux/slab.h>
0020 #include "leds.h"
0021
0022 struct led_pwm {
0023     const char  *name;
0024     u8      active_low;
0025     u8      default_state;
0026     unsigned int    max_brightness;
0027 };
0028
0029 struct led_pwm_data {
0030     struct led_classdev cdev;
0031     struct pwm_device   *pwm;
0032     struct pwm_state    pwmstate;
0033     unsigned int        active_low;
0034 };
0035
0036 struct led_pwm_priv {
0037     int num_leds;
0038     struct led_pwm_data leds[];
0039 };
0040
0041 static int led_pwm_set(struct led_classdev *led_cdev,
0042                enum led_brightness brightness)
0043 {
0044     struct led_pwm_data *led_dat =
0045         container_of(led_cdev, struct led_pwm_data, cdev);
0046     unsigned int max = led_dat->cdev.max_brightness;
0047     unsigned long long duty = led_dat->pwmstate.period;
0048
0049     duty *= brightness;
0050     do_div(duty, max);
0051
0052     if (led_dat->active_low)
0053         duty = led_dat->pwmstate.period - duty;
0054
0055     led_dat->pwmstate.duty_cycle = duty;
0056     led_dat->pwmstate.enabled = duty > 0;
0057     return pwm_apply_state(led_dat->pwm, &led_dat->pwmstate);
0058 }
0059
0060 __attribute__((nonnull))
0061 static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
0062                struct led_pwm *led, struct fwnode_handle *fwnode)
0063 {
0064     struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
0065     struct led_init_data init_data = { .fwnode = fwnode };
0066     int ret;
0067
0068     led_data->active_low = led->active_low;
0069     led_data->cdev.name = led->name;
0070     led_data->cdev.brightness = LED_OFF;
0071     led_data->cdev.max_brightness = led->max_brightness;
0072     led_data->cdev.flags = LED_CORE_SUSPENDRESUME;
0073
0074     led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, NULL);
0075     if (IS_ERR(led_data->pwm))
0076         return dev_err_probe(dev, PTR_ERR(led_data->pwm),
0077                      "unable to request PWM for %s\n",
0078                      led->name);
0079
0080     led_data->cdev.brightness_set_blocking = led_pwm_set;
0081
0082     /* init PWM state */
0083     switch (led->default_state) {
0084     case LEDS_DEFSTATE_KEEP:
0085         pwm_get_state(led_data->pwm, &led_data->pwmstate);
0086         if (led_data->pwmstate.period)
0087             break;
0088         led->default_state = LEDS_DEFSTATE_OFF;
0089         dev_warn(dev,
0090             "failed to read period for %s, default to off",
0091             led->name);
0092         fallthrough;
0093     default:
0094         pwm_init_state(led_data->pwm, &led_data->pwmstate);
0095         break;
0096     }
0097
0098     /* set brightness */
0099     switch (led->default_state) {
0100     case LEDS_DEFSTATE_ON:
0101         led_data->cdev.brightness = led->max_brightness;
0102         break;
0103     case LEDS_DEFSTATE_KEEP:
0104         {
0105         uint64_t brightness;
0106
0107         brightness = led->max_brightness;
0108         brightness *= led_data->pwmstate.duty_cycle;
0109         do_div(brightness, led_data->pwmstate.period);
0110         led_data->cdev.brightness = brightness;
0111         }
0112         break;
0113     }
0114
0115     ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
0116     if (ret) {
0117         dev_err(dev, "failed to register PWM led for %s: %d\n",
0118             led->name, ret);
0119         return ret;
0120     }
0121
0122     if (led->default_state != LEDS_DEFSTATE_KEEP) {
0123         ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
0124         if (ret) {
0125             dev_err(dev, "failed to set led PWM value for %s: %d",
0126                 led->name, ret);
0127             return ret;
0128         }
0129     }
0130
0131     priv->num_leds++;
0132     return 0;
0133 }
0134
0135 static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
0136 {
0137     struct fwnode_handle *fwnode;
0138     struct led_pwm led;
0139     int ret;
0140
0141     memset(&led, 0, sizeof(led));
0142
0143     device_for_each_child_node(dev, fwnode) {
0144         ret = fwnode_property_read_string(fwnode, "label", &led.name);
0145         if (ret && is_of_node(fwnode))
0146             led.name = to_of_node(fwnode)->name;
0147
0148         if (!led.name) {
0149             ret = EINVAL;
0150             goto err_child_out;
0151         }
0152
0153         led.active_low = fwnode_property_read_bool(fwnode,
0154                                "active-low");
0155         fwnode_property_read_u32(fwnode, "max-brightness",
0156                      &led.max_brightness);
0157
0158         led.default_state = led_init_default_state_get(fwnode);
0159
0160         ret = led_pwm_add(dev, priv, &led, fwnode);
0161         if (ret)
0162             goto err_child_out;
0163     }
0164
0165     return 0;
0166
0167 err_child_out:
0168     fwnode_handle_put(fwnode);
0169     return ret;
0170 }
0171
0172 static int led_pwm_probe(struct platform_device *pdev)
0173 {
0174     struct led_pwm_priv *priv;
0175     int ret = 0;
0176     int count;
0177
0178     count = device_get_child_node_count(&pdev->dev);
0179
0180     if (!count)
0181         return -EINVAL;
0182
0183     priv = devm_kzalloc(&pdev->dev, struct_size(priv, leds, count),
0184                 GFP_KERNEL);
0185     if (!priv)
0186         return -ENOMEM;
0187
0188     ret = led_pwm_create_fwnode(&pdev->dev, priv);
0189
0190     if (ret)
0191         return ret;
0192
0193     platform_set_drvdata(pdev, priv);
0194
0195     return 0;
0196 }
0197
0198 static const struct of_device_id of_pwm_leds_match[] = {
0199     { .compatible = "pwm-leds", },
0200     {},
0201 };
0202 MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
0203
0204 static struct platform_driver led_pwm_driver = {
0205     .probe      = led_pwm_probe,
0206     .driver     = {
0207         .name   = "leds_pwm",
0208         .of_match_table = of_pwm_leds_match,
0209     },
0210 };
0211
0212 module_platform_driver(led_pwm_driver);
0213
0214 MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>");
0215 MODULE_DESCRIPTION("generic PWM LED driver");
0216 MODULE_LICENSE("GPL v2");
0217 MODULE_ALIAS("platform:leds-pwm");