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/mod_devicetable.h> 10 #include <linux/platform_device.h> 11 #include <linux/property.h> 12 13 #define KTD2801_DEFAULT_BRIGHTNESS 100 14 #define KTD2801_MAX_BRIGHTNESS 255 15 16 /* These values have been extracted from Samsung's driver. */ 17 static const struct expresswire_timing ktd2801_timing = { 18 .poweroff_us = 2600, 19 .detect_delay_us = 150, 20 .detect_us = 270, 21 .data_start_us = 5, 22 .short_bitset_us = 5, 23 .long_bitset_us = 15, 24 .end_of_data_low_us = 10, 25 .end_of_data_high_us = 350 26 }; 27 28 struct ktd2801_backlight { 29 struct expresswire_common_props props; 30 struct backlight_device *bd; 31 bool was_on; 32 }; 33 34 static int ktd2801_update_status(struct backlight_device *bd) 35 { 36 struct ktd2801_backlight *ktd2801 = bl_get_data(bd); 37 u8 brightness = (u8) backlight_get_brightness(bd); 38 39 if (backlight_is_blank(bd)) { 40 expresswire_power_off(&ktd2801->props); 41 ktd2801->was_on = false; 42 return 0; 43 } 44 45 if (!ktd2801->was_on) { 46 expresswire_enable(&ktd2801->props); 47 ktd2801->was_on = true; 48 } 49 50 expresswire_write_u8(&ktd2801->props, brightness); 51 52 return 0; 53 } 54 55 static const struct backlight_ops ktd2801_backlight_ops = { 56 .options = BL_CORE_SUSPENDRESUME, 57 .update_status = ktd2801_update_status, 58 }; 59 60 static int ktd2801_backlight_probe(struct platform_device *pdev) 61 { 62 struct device *dev = &pdev->dev; 63 struct backlight_device *bd; 64 struct ktd2801_backlight *ktd2801; 65 u32 brightness, max_brightness; 66 int ret; 67 68 ktd2801 = devm_kzalloc(dev, sizeof(*ktd2801), GFP_KERNEL); 69 if (!ktd2801) 70 return -ENOMEM; 71 ktd2801->was_on = true; 72 ktd2801->props.timing = ktd2801_timing; 73 74 ret = device_property_read_u32(dev, "max-brightness", &max_brightness); 75 if (ret) 76 max_brightness = KTD2801_MAX_BRIGHTNESS; 77 if (max_brightness > KTD2801_MAX_BRIGHTNESS) { 78 dev_err(dev, "illegal max brightness specified\n"); 79 max_brightness = KTD2801_MAX_BRIGHTNESS; 80 } 81 82 ret = device_property_read_u32(dev, "default-brightness", &brightness); 83 if (ret) 84 brightness = KTD2801_DEFAULT_BRIGHTNESS; 85 if (brightness > max_brightness) { 86 dev_err(dev, "default brightness exceeds max\n"); 87 brightness = max_brightness; 88 } 89 90 ktd2801->props.ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_OUT_HIGH); 91 if (IS_ERR(ktd2801->props.ctrl_gpio)) 92 return dev_err_probe(dev, PTR_ERR(ktd2801->props.ctrl_gpio), 93 "failed to get backlight GPIO"); 94 gpiod_set_consumer_name(ktd2801->props.ctrl_gpio, dev_name(dev)); 95 96 bd = devm_backlight_device_register(dev, dev_name(dev), dev, ktd2801, 97 &ktd2801_backlight_ops, NULL); 98 if (IS_ERR(bd)) 99 return dev_err_probe(dev, PTR_ERR(bd), 100 "failed to register backlight"); 101 102 bd->props.max_brightness = max_brightness; 103 bd->props.brightness = brightness; 104 105 ktd2801->bd = bd; 106 platform_set_drvdata(pdev, bd); 107 backlight_update_status(bd); 108 109 return 0; 110 } 111 112 static const struct of_device_id ktd2801_of_match[] = { 113 { .compatible = "kinetic,ktd2801" }, 114 { } 115 }; 116 MODULE_DEVICE_TABLE(of, ktd2801_of_match); 117 118 static struct platform_driver ktd2801_backlight_driver = { 119 .driver = { 120 .name = "ktd2801-backlight", 121 .of_match_table = ktd2801_of_match, 122 }, 123 .probe = ktd2801_backlight_probe, 124 }; 125 module_platform_driver(ktd2801_backlight_driver); 126 127 MODULE_IMPORT_NS("EXPRESSWIRE"); 128 MODULE_AUTHOR("Duje Mihanović <duje.mihanovic@skole.hr>"); 129 MODULE_DESCRIPTION("Kinetic KTD2801 Backlight Driver"); 130 MODULE_LICENSE("GPL"); 131