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