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