1 // SPDX-License-Identifier: GPL-2.0 OR MIT
2 /*
3 * Driver for backlight controllers attached via Apple DWI 2-wire interface
4 *
5 * Copyright (c) 2024 Nick Chan <towinchenmi@gmail.com>
6 */
7
8 #include <linux/backlight.h>
9 #include <linux/bitfield.h>
10 #include <linux/device.h>
11 #include <linux/io.h>
12 #include <linux/mod_devicetable.h>
13 #include <linux/module.h>
14 #include <linux/platform_device.h>
15
16 #define DWI_BL_CTL 0x0
17 #define DWI_BL_CTL_SEND1 BIT(0)
18 #define DWI_BL_CTL_SEND2 BIT(4)
19 #define DWI_BL_CTL_SEND3 BIT(5)
20 #define DWI_BL_CTL_LE_DATA BIT(6)
21 /* Only used on Apple A9 and later */
22 #define DWI_BL_CTL_SEND4 BIT(12)
23
24 #define DWI_BL_CMD 0x4
25 #define DWI_BL_CMD_TYPE GENMASK(31, 28)
26 #define DWI_BL_CMD_TYPE_SET_BRIGHTNESS 0xa
27 #define DWI_BL_CMD_DATA GENMASK(10, 0)
28
29 #define DWI_BL_CTL_SEND (DWI_BL_CTL_SEND1 | \
30 DWI_BL_CTL_SEND2 | \
31 DWI_BL_CTL_SEND3 | \
32 DWI_BL_CTL_LE_DATA | \
33 DWI_BL_CTL_SEND4)
34
35 #define DWI_BL_MAX_BRIGHTNESS 2047
36
37 struct apple_dwi_bl {
38 void __iomem *base;
39 };
40
dwi_bl_update_status(struct backlight_device * bl)41 static int dwi_bl_update_status(struct backlight_device *bl)
42 {
43 struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
44
45 int brightness = backlight_get_brightness(bl);
46
47 u32 cmd = 0;
48
49 cmd |= FIELD_PREP(DWI_BL_CMD_DATA, brightness);
50 cmd |= FIELD_PREP(DWI_BL_CMD_TYPE, DWI_BL_CMD_TYPE_SET_BRIGHTNESS);
51
52 writel(cmd, dwi_bl->base + DWI_BL_CMD);
53 writel(DWI_BL_CTL_SEND, dwi_bl->base + DWI_BL_CTL);
54
55 return 0;
56 }
57
dwi_bl_get_brightness(struct backlight_device * bl)58 static int dwi_bl_get_brightness(struct backlight_device *bl)
59 {
60 struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
61
62 u32 cmd = readl(dwi_bl->base + DWI_BL_CMD);
63
64 return FIELD_GET(DWI_BL_CMD_DATA, cmd);
65 }
66
67 static const struct backlight_ops dwi_bl_ops = {
68 .options = BL_CORE_SUSPENDRESUME,
69 .get_brightness = dwi_bl_get_brightness,
70 .update_status = dwi_bl_update_status
71 };
72
dwi_bl_probe(struct platform_device * dev)73 static int dwi_bl_probe(struct platform_device *dev)
74 {
75 struct apple_dwi_bl *dwi_bl;
76 struct backlight_device *bl;
77 struct backlight_properties props;
78 struct resource *res;
79
80 dwi_bl = devm_kzalloc(&dev->dev, sizeof(*dwi_bl), GFP_KERNEL);
81 if (!dwi_bl)
82 return -ENOMEM;
83
84 dwi_bl->base = devm_platform_get_and_ioremap_resource(dev, 0, &res);
85 if (IS_ERR(dwi_bl->base))
86 return PTR_ERR(dwi_bl->base);
87
88 memset(&props, 0, sizeof(struct backlight_properties));
89 props.type = BACKLIGHT_PLATFORM;
90 props.max_brightness = DWI_BL_MAX_BRIGHTNESS;
91 props.scale = BACKLIGHT_SCALE_LINEAR;
92
93 bl = devm_backlight_device_register(&dev->dev, dev->name, &dev->dev,
94 dwi_bl, &dwi_bl_ops, &props);
95 if (IS_ERR(bl))
96 return PTR_ERR(bl);
97
98 platform_set_drvdata(dev, dwi_bl);
99
100 bl->props.brightness = dwi_bl_get_brightness(bl);
101
102 return 0;
103 }
104
105 static const struct of_device_id dwi_bl_of_match[] = {
106 { .compatible = "apple,dwi-bl" },
107 {},
108 };
109
110 MODULE_DEVICE_TABLE(of, dwi_bl_of_match);
111
112 static struct platform_driver dwi_bl_driver = {
113 .driver = {
114 .name = "apple-dwi-bl",
115 .of_match_table = dwi_bl_of_match
116 },
117 .probe = dwi_bl_probe,
118 };
119
120 module_platform_driver(dwi_bl_driver);
121
122 MODULE_DESCRIPTION("Apple DWI Backlight Driver");
123 MODULE_AUTHOR("Nick Chan <towinchenmi@gmail.com>");
124 MODULE_LICENSE("Dual MIT/GPL");
125