drivers/leds/leds-lt3593.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2009,2018 Daniel Mack <daniel@zonque.org>
   3
   4 #include <linux/kernel.h>
   5 #include <linux/platform_device.h>
   6 #include <linux/leds.h>
   7 #include <linux/delay.h>
   8 #include <linux/gpio/consumer.h>
   9 #include <linux/slab.h>
  10 #include <linux/module.h>
  11 #include <linux/of.h>
  12
  13 #define LED_LT3593_NAME "lt3593"
  14
  15 struct lt3593_led_data {
  16         struct led_classdev cdev;
  17         struct gpio_desc *gpiod;
  18 };
  19
  20 static int lt3593_led_set(struct led_classdev *led_cdev,
  21                            enum led_brightness value)
  22 {
  23         struct lt3593_led_data *led_dat =
  24                 container_of(led_cdev, struct lt3593_led_data, cdev);
  25         int pulses;
  26
  27         /*
  28          * The LT3593 resets its internal current level register to the maximum
  29          * level on the first falling edge on the control pin. Each following
  30          * falling edge decreases the current level by 625uA. Up to 32 pulses
  31          * can be sent, so the maximum power reduction is 20mA.
  32          * After a timeout of 128us, the value is taken from the register and
  33          * applied is to the output driver.
  34          */
  35
  36         if (value == 0) {
  37                 gpiod_set_value_cansleep(led_dat->gpiod, 0);
  38                 return 0;
  39         }
  40
  41         pulses = 32 - (value * 32) / 255;
  42
  43         if (pulses == 0) {
  44                 gpiod_set_value_cansleep(led_dat->gpiod, 0);
  45                 mdelay(1);
  46                 gpiod_set_value_cansleep(led_dat->gpiod, 1);
  47                 return 0;
  48         }
  49
  50         gpiod_set_value_cansleep(led_dat->gpiod, 1);
  51
  52         while (pulses--) {
  53                 gpiod_set_value_cansleep(led_dat->gpiod, 0);
  54                 udelay(1);
  55                 gpiod_set_value_cansleep(led_dat->gpiod, 1);
  56                 udelay(1);
  57         }
  58
  59         return 0;
  60 }
  61
  62 static int lt3593_led_probe(struct platform_device *pdev)
  63 {
  64         struct device *dev = &pdev->dev;
  65         struct lt3593_led_data *led_data;
  66         struct fwnode_handle *child;
  67         int ret, state = LEDS_GPIO_DEFSTATE_OFF;
  68         struct led_init_data init_data = {};
  69         const char *tmp;
  70
  71         if (!dev_of_node(dev))
  72                 return -ENODEV;
  73
  74         led_data = devm_kzalloc(dev, sizeof(*led_data), GFP_KERNEL);
  75         if (!led_data)
  76                 return -ENOMEM;
  77
  78         if (device_get_child_node_count(dev) != 1) {
  79                 dev_err(dev, "Device must have exactly one LED sub-node.");
  80                 return -EINVAL;
  81         }
  82
  83         led_data->gpiod = devm_gpiod_get(dev, "lltc,ctrl", 0);
  84         if (IS_ERR(led_data->gpiod))
  85                 return PTR_ERR(led_data->gpiod);
  86
  87         child = device_get_next_child_node(dev, NULL);
  88
  89         if (!fwnode_property_read_string(child, "default-state", &tmp)) {
  90                 if (!strcmp(tmp, "on"))
  91                         state = LEDS_GPIO_DEFSTATE_ON;
  92         }
  93
  94         led_data->cdev.brightness_set_blocking = lt3593_led_set;
  95         led_data->cdev.brightness = state ? LED_FULL : LED_OFF;
  96
  97         init_data.fwnode = child;
  98         init_data.devicename = LED_LT3593_NAME;
  99         init_data.default_label = ":";
 100
 101         ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
 102         if (ret < 0) {
 103                 fwnode_handle_put(child);
 104                 return ret;
 105         }
 106
 107         platform_set_drvdata(pdev, led_data);
 108
 109         return 0;
 110 }
 111
 112 static const struct of_device_id of_lt3593_leds_match[] = {
 113         { .compatible = "lltc,lt3593", },
 114         {},
 115 };
 116 MODULE_DEVICE_TABLE(of, of_lt3593_leds_match);
 117
 118 static struct platform_driver lt3593_led_driver = {
 119         .probe          = lt3593_led_probe,
 120         .driver         = {
 121                 .name   = "leds-lt3593",
 122                 .of_match_table = of_match_ptr(of_lt3593_leds_match),
 123         },
 124 };
 125
 126 module_platform_driver(lt3593_led_driver);
 127
 128 MODULE_AUTHOR("Daniel Mack <daniel@zonque.org>");
 129 MODULE_DESCRIPTION("LED driver for LT3593 controllers");
 130 MODULE_LICENSE("GPL v2");
 131 MODULE_ALIAS("platform:leds-lt3593");