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