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// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
* Driver for backlight controllers attached via Apple DWI 2-wire interface
*
* Copyright (c) 2024 Nick Chan <towinchenmi@gmail.com>
*/
#include <linux/backlight.h>
#include <linux/bitfield.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#define DWI_BL_CTL 0x0
#define DWI_BL_CTL_SEND1 BIT(0)
#define DWI_BL_CTL_SEND2 BIT(4)
#define DWI_BL_CTL_SEND3 BIT(5)
#define DWI_BL_CTL_LE_DATA BIT(6)
/* Only used on Apple A9 and later */
#define DWI_BL_CTL_SEND4 BIT(12)
#define DWI_BL_CMD 0x4
#define DWI_BL_CMD_TYPE GENMASK(31, 28)
#define DWI_BL_CMD_TYPE_SET_BRIGHTNESS 0xa
#define DWI_BL_CMD_DATA GENMASK(10, 0)
#define DWI_BL_CTL_SEND (DWI_BL_CTL_SEND1 | \
DWI_BL_CTL_SEND2 | \
DWI_BL_CTL_SEND3 | \
DWI_BL_CTL_LE_DATA | \
DWI_BL_CTL_SEND4)
#define DWI_BL_MAX_BRIGHTNESS 2047
struct apple_dwi_bl {
void __iomem *base;
};
static int dwi_bl_update_status(struct backlight_device *bl)
{
struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
int brightness = backlight_get_brightness(bl);
u32 cmd = 0;
cmd |= FIELD_PREP(DWI_BL_CMD_DATA, brightness);
cmd |= FIELD_PREP(DWI_BL_CMD_TYPE, DWI_BL_CMD_TYPE_SET_BRIGHTNESS);
writel(cmd, dwi_bl->base + DWI_BL_CMD);
writel(DWI_BL_CTL_SEND, dwi_bl->base + DWI_BL_CTL);
return 0;
}
static int dwi_bl_get_brightness(struct backlight_device *bl)
{
struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
u32 cmd = readl(dwi_bl->base + DWI_BL_CMD);
return FIELD_GET(DWI_BL_CMD_DATA, cmd);
}
static const struct backlight_ops dwi_bl_ops = {
.options = BL_CORE_SUSPENDRESUME,
.get_brightness = dwi_bl_get_brightness,
.update_status = dwi_bl_update_status
};
static int dwi_bl_probe(struct platform_device *dev)
{
struct apple_dwi_bl *dwi_bl;
struct backlight_device *bl;
struct backlight_properties props;
struct resource *res;
dwi_bl = devm_kzalloc(&dev->dev, sizeof(*dwi_bl), GFP_KERNEL);
if (!dwi_bl)
return -ENOMEM;
dwi_bl->base = devm_platform_get_and_ioremap_resource(dev, 0, &res);
if (IS_ERR(dwi_bl->base))
return PTR_ERR(dwi_bl->base);
memset(&props, 0, sizeof(struct backlight_properties));
props.type = BACKLIGHT_PLATFORM;
props.max_brightness = DWI_BL_MAX_BRIGHTNESS;
props.scale = BACKLIGHT_SCALE_LINEAR;
bl = devm_backlight_device_register(&dev->dev, dev->name, &dev->dev,
dwi_bl, &dwi_bl_ops, &props);
if (IS_ERR(bl))
return PTR_ERR(bl);
platform_set_drvdata(dev, dwi_bl);
bl->props.brightness = dwi_bl_get_brightness(bl);
return 0;
}
static const struct of_device_id dwi_bl_of_match[] = {
{ .compatible = "apple,dwi-bl" },
{},
};
MODULE_DEVICE_TABLE(of, dwi_bl_of_match);
static struct platform_driver dwi_bl_driver = {
.driver = {
.name = "apple-dwi-bl",
.of_match_table = dwi_bl_of_match
},
.probe = dwi_bl_probe,
};
module_platform_driver(dwi_bl_driver);
MODULE_DESCRIPTION("Apple DWI Backlight Driver");
MODULE_AUTHOR("Nick Chan <towinchenmi@gmail.com>");
MODULE_LICENSE("Dual MIT/GPL");
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