// 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/mod_devicetable.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");