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/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. */
 17static 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
 28struct ktd2801_backlight {
 29	struct expresswire_common_props props;
 30	struct backlight_device *bd;
 31	bool was_on;
 32};
 33
 34static 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
 55static const struct backlight_ops ktd2801_backlight_ops = {
 56	.update_status = ktd2801_update_status,
 57};
 58
 59static int ktd2801_backlight_probe(struct platform_device *pdev)
 60{
 61	struct device *dev = &pdev->dev;
 62	struct backlight_device *bd;
 63	struct ktd2801_backlight *ktd2801;
 64	u32 brightness, max_brightness;
 65	int ret;
 66
 67	ktd2801 = devm_kzalloc(dev, sizeof(*ktd2801), GFP_KERNEL);
 68	if (!ktd2801)
 69		return -ENOMEM;
 70	ktd2801->was_on = true;
 71	ktd2801->props.timing = ktd2801_timing;
 72
 73	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
 74	if (ret)
 75		max_brightness = KTD2801_MAX_BRIGHTNESS;
 76	if (max_brightness > KTD2801_MAX_BRIGHTNESS) {
 77		dev_err(dev, "illegal max brightness specified\n");
 78		max_brightness = KTD2801_MAX_BRIGHTNESS;
 79	}
 80
 81	ret = device_property_read_u32(dev, "default-brightness", &brightness);
 82	if (ret)
 83		brightness = KTD2801_DEFAULT_BRIGHTNESS;
 84	if (brightness > max_brightness) {
 85		dev_err(dev, "default brightness exceeds max\n");
 86		brightness = max_brightness;
 87	}
 88
 89	ktd2801->props.ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_OUT_HIGH);
 90	if (IS_ERR(ktd2801->props.ctrl_gpio))
 91		return dev_err_probe(dev, PTR_ERR(ktd2801->props.ctrl_gpio),
 92				"failed to get backlight GPIO");
 93	gpiod_set_consumer_name(ktd2801->props.ctrl_gpio, dev_name(dev));
 94
 95	bd = devm_backlight_device_register(dev, dev_name(dev), dev, ktd2801,
 96			&ktd2801_backlight_ops, NULL);
 97	if (IS_ERR(bd))
 98		return dev_err_probe(dev, PTR_ERR(bd),
 99				"failed to register backlight");
100
101	bd->props.max_brightness = max_brightness;
102	bd->props.brightness = brightness;
103
104	ktd2801->bd = bd;
105	platform_set_drvdata(pdev, bd);
106	backlight_update_status(bd);
107
108	return 0;
109}
110
111static const struct of_device_id ktd2801_of_match[] = {
112	{ .compatible = "kinetic,ktd2801" },
113	{ }
114};
115MODULE_DEVICE_TABLE(of, ktd2801_of_match);
116
117static struct platform_driver ktd2801_backlight_driver = {
118	.driver = {
119		.name = "ktd2801-backlight",
120		.of_match_table = ktd2801_of_match,
121	},
122	.probe = ktd2801_backlight_probe,
123};
124module_platform_driver(ktd2801_backlight_driver);
125
126MODULE_IMPORT_NS("EXPRESSWIRE");
127MODULE_AUTHOR("Duje Mihanović <duje.mihanovic@skole.hr>");
128MODULE_DESCRIPTION("Kinetic KTD2801 Backlight Driver");
129MODULE_LICENSE("GPL");