// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2015, Samsung Electronics Co., Ltd.
 *
 * Author: Marek Szyprowski <m.szyprowski@samsung.com>
 *
 * Simple eMMC hardware reset provider
 */
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/reboot.h>

#include <linux/mmc/host.h>

#include "pwrseq.h"

struct mmc_pwrseq_emmc {
        struct mmc_pwrseq pwrseq;
        struct notifier_block reset_nb;
        struct gpio_desc *reset_gpio;
};

#define to_pwrseq_emmc(p) container_of(p, struct mmc_pwrseq_emmc, pwrseq)

static void mmc_pwrseq_emmc_reset(struct mmc_host *host)
{
        struct mmc_pwrseq_emmc *pwrseq =  to_pwrseq_emmc(host->pwrseq);

        gpiod_set_value_cansleep(pwrseq->reset_gpio, 1);
        udelay(1);
        gpiod_set_value_cansleep(pwrseq->reset_gpio, 0);
        udelay(200);
}

static int mmc_pwrseq_emmc_reset_nb(struct notifier_block *this,
                                    unsigned long mode, void *cmd)
{
        struct mmc_pwrseq_emmc *pwrseq = container_of(this,
                                        struct mmc_pwrseq_emmc, reset_nb);
        gpiod_set_value(pwrseq->reset_gpio, 1);
        udelay(1);
        gpiod_set_value(pwrseq->reset_gpio, 0);
        udelay(200);

        return NOTIFY_DONE;
}

static const struct mmc_pwrseq_ops mmc_pwrseq_emmc_ops = {
        .reset = mmc_pwrseq_emmc_reset,
};

static int mmc_pwrseq_emmc_probe(struct platform_device *pdev)
{
        struct mmc_pwrseq_emmc *pwrseq;
        struct device *dev = &pdev->dev;

        pwrseq = devm_kzalloc(dev, sizeof(*pwrseq), GFP_KERNEL);
        if (!pwrseq)
                return -ENOMEM;

        pwrseq->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
        if (IS_ERR(pwrseq->reset_gpio))
                return PTR_ERR(pwrseq->reset_gpio);

        if (!gpiod_cansleep(pwrseq->reset_gpio)) {
                /*
                 * register reset handler to ensure emmc reset also from
                 * emergency_reboot(), priority 255 is the highest priority
                 * so it will be executed before any system reboot handler.
                 */
                pwrseq->reset_nb.notifier_call = mmc_pwrseq_emmc_reset_nb;
                pwrseq->reset_nb.priority = 255;
                register_restart_handler(&pwrseq->reset_nb);
        } else {
                dev_notice(dev, "EMMC reset pin tied to a sleepy GPIO driver; reset on emergency-reboot disabled\n");
        }

        pwrseq->pwrseq.ops = &mmc_pwrseq_emmc_ops;
        pwrseq->pwrseq.dev = dev;
        pwrseq->pwrseq.owner = THIS_MODULE;
        platform_set_drvdata(pdev, pwrseq);

        return mmc_pwrseq_register(&pwrseq->pwrseq);
}

static void mmc_pwrseq_emmc_remove(struct platform_device *pdev)
{
        struct mmc_pwrseq_emmc *pwrseq = platform_get_drvdata(pdev);

        unregister_restart_handler(&pwrseq->reset_nb);
        mmc_pwrseq_unregister(&pwrseq->pwrseq);
}

static const struct of_device_id mmc_pwrseq_emmc_of_match[] = {
        { .compatible = "mmc-pwrseq-emmc",},
        {/* sentinel */},
};

MODULE_DEVICE_TABLE(of, mmc_pwrseq_emmc_of_match);

static struct platform_driver mmc_pwrseq_emmc_driver = {
        .probe = mmc_pwrseq_emmc_probe,
        .remove = mmc_pwrseq_emmc_remove,
        .driver = {
                .name = "pwrseq_emmc",
                .of_match_table = mmc_pwrseq_emmc_of_match,
        },
};

module_platform_driver(mmc_pwrseq_emmc_driver);
MODULE_DESCRIPTION("Hardware reset support for eMMC");
MODULE_LICENSE("GPL v2");