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 
ktd2801_update_status(struct backlight_device * bd)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 
ktd2801_backlight_probe(struct platform_device * pdev)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