drivers/video/backlight/ktd2801-backlight.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Datasheet:
   4  * https://www.kinet-ic.com/uploads/web/KTD2801/KTD2801-04b.pdf
   5  */
   6 #include <linux/backlight.h>
   7 #include <linux/gpio/consumer.h>
   8 #include <linux/leds-expresswire.h>
   9 #include <linux/platform_device.h>
  10 #include <linux/property.h>
  11
  12 #define KTD2801_DEFAULT_BRIGHTNESS      100
  13 #define KTD2801_MAX_BRIGHTNESS          255
  14
  15 /* These values have been extracted from Samsung's driver. */
  16 static const struct expresswire_timing ktd2801_timing = {
  17         .poweroff_us = 2600,
  18         .detect_delay_us = 150,
  19         .detect_us = 270,
  20         .data_start_us = 5,
  21         .short_bitset_us = 5,
  22         .long_bitset_us = 15,
  23         .end_of_data_low_us = 10,
  24         .end_of_data_high_us = 350
  25 };
  26
  27 struct ktd2801_backlight {
  28         struct expresswire_common_props props;
  29         struct backlight_device *bd;
  30         bool was_on;
  31 };
  32
  33 static int ktd2801_update_status(struct backlight_device *bd)
  34 {
  35         struct ktd2801_backlight *ktd2801 = bl_get_data(bd);
  36         u8 brightness = (u8) backlight_get_brightness(bd);
  37
  38         if (backlight_is_blank(bd)) {
  39                 expresswire_power_off(&ktd2801->props);
  40                 ktd2801->was_on = false;
  41                 return 0;
  42         }
  43
  44         if (!ktd2801->was_on) {
  45                 expresswire_enable(&ktd2801->props);
  46                 ktd2801->was_on = true;
  47         }
  48
  49         expresswire_write_u8(&ktd2801->props, brightness);
  50
  51         return 0;
  52 }
  53
  54 static const struct backlight_ops ktd2801_backlight_ops = {
  55         .update_status = ktd2801_update_status,
  56 };
  57
  58 static int ktd2801_backlight_probe(struct platform_device *pdev)
  59 {
  60         struct device *dev = &pdev->dev;
  61         struct backlight_device *bd;
  62         struct ktd2801_backlight *ktd2801;
  63         u32 brightness, max_brightness;
  64         int ret;
  65
  66         ktd2801 = devm_kzalloc(dev, sizeof(*ktd2801), GFP_KERNEL);
  67         if (!ktd2801)
  68                 return -ENOMEM;
  69         ktd2801->was_on = true;
  70         ktd2801->props.timing = ktd2801_timing;
  71
  72         ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
  73         if (ret)
  74                 max_brightness = KTD2801_MAX_BRIGHTNESS;
  75         if (max_brightness > KTD2801_MAX_BRIGHTNESS) {
  76                 dev_err(dev, "illegal max brightness specified\n");
  77                 max_brightness = KTD2801_MAX_BRIGHTNESS;
  78         }
  79
  80         ret = device_property_read_u32(dev, "default-brightness", &brightness);
  81         if (ret)
  82                 brightness = KTD2801_DEFAULT_BRIGHTNESS;
  83         if (brightness > max_brightness) {
  84                 dev_err(dev, "default brightness exceeds max\n");
  85                 brightness = max_brightness;
  86         }
  87
  88         ktd2801->props.ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_OUT_HIGH);
  89         if (IS_ERR(ktd2801->props.ctrl_gpio))
  90                 return dev_err_probe(dev, PTR_ERR(ktd2801->props.ctrl_gpio),
  91                                 "failed to get backlight GPIO");
  92         gpiod_set_consumer_name(ktd2801->props.ctrl_gpio, dev_name(dev));
  93
  94         bd = devm_backlight_device_register(dev, dev_name(dev), dev, ktd2801,
  95                         &ktd2801_backlight_ops, NULL);
  96         if (IS_ERR(bd))
  97                 return dev_err_probe(dev, PTR_ERR(bd),
  98                                 "failed to register backlight");
  99
 100         bd->props.max_brightness = max_brightness;
 101         bd->props.brightness = brightness;
 102
 103         ktd2801->bd = bd;
 104         platform_set_drvdata(pdev, bd);
 105         backlight_update_status(bd);
 106
 107         return 0;
 108 }
 109
 110 static const struct of_device_id ktd2801_of_match[] = {
 111         { .compatible = "kinetic,ktd2801" },
 112         { }
 113 };
 114 MODULE_DEVICE_TABLE(of, ktd2801_of_match);
 115
 116 static struct platform_driver ktd2801_backlight_driver = {
 117         .driver = {
 118                 .name = "ktd2801-backlight",
 119                 .of_match_table = ktd2801_of_match,
 120         },
 121         .probe = ktd2801_backlight_probe,
 122 };
 123 module_platform_driver(ktd2801_backlight_driver);
 124
 125 MODULE_IMPORT_NS(EXPRESSWIRE);
 126 MODULE_AUTHOR("Duje Mihanović <duje.mihanovic@skole.hr>");
 127 MODULE_DESCRIPTION("Kinetic KTD2801 Backlight Driver");
 128 MODULE_LICENSE("GPL");