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
ktd2801_update_status(struct backlight_device * bd)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 .update_status = ktd2801_update_status,
57 };
58
ktd2801_backlight_probe(struct platform_device * pdev)59 static 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
111 static const struct of_device_id ktd2801_of_match[] = {
112 { .compatible = "kinetic,ktd2801" },
113 { }
114 };
115 MODULE_DEVICE_TABLE(of, ktd2801_of_match);
116
117 static 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 };
124 module_platform_driver(ktd2801_backlight_driver);
125
126 MODULE_IMPORT_NS("EXPRESSWIRE");
127 MODULE_AUTHOR("Duje Mihanović <duje.mihanovic@skole.hr>");
128 MODULE_DESCRIPTION("Kinetic KTD2801 Backlight Driver");
129 MODULE_LICENSE("GPL");
130