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/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
37struct apple_dwi_bl {
38 void __iomem *base;
39};
40
41static 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
58static 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
67static 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
73static 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
105static const struct of_device_id dwi_bl_of_match[] = {
106 { .compatible = "apple,dwi-bl" },
107 {},
108};
109
110MODULE_DEVICE_TABLE(of, dwi_bl_of_match);
111
112static 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
120module_platform_driver(dwi_bl_driver);
121
122MODULE_DESCRIPTION("Apple DWI Backlight Driver");
123MODULE_AUTHOR("Nick Chan <towinchenmi@gmail.com>");
124MODULE_LICENSE("Dual MIT/GPL");