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"); 129