// SPDX-License-Identifier: GPL-2.0
/*
 * MStar WDT driver
 *
 * Copyright (C) 2019 - 2021 Daniel Palmer
 * Copyright (C) 2021 Romain Perier
 *
 */

#include <linux/clk.h>
#include <linux/io.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>

#define REG_WDT_CLR                     0x0
#define REG_WDT_MAX_PRD_L               0x10
#define REG_WDT_MAX_PRD_H               0x14

#define MSC313E_WDT_MIN_TIMEOUT         1
#define MSC313E_WDT_DEFAULT_TIMEOUT     30

static unsigned int timeout;

module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");

struct msc313e_wdt_priv {
        void __iomem *base;
        struct watchdog_device wdev;
        struct clk *clk;
};

static int msc313e_wdt_start(struct watchdog_device *wdev)
{
        struct msc313e_wdt_priv *priv = watchdog_get_drvdata(wdev);
        u32 timeout;
        int err;

        err = clk_prepare_enable(priv->clk);
        if (err)
                return err;

        timeout = wdev->timeout * clk_get_rate(priv->clk);
        writew(timeout & 0xffff, priv->base + REG_WDT_MAX_PRD_L);
        writew((timeout >> 16) & 0xffff, priv->base + REG_WDT_MAX_PRD_H);
        writew(1, priv->base + REG_WDT_CLR);
        return 0;
}

static int msc313e_wdt_ping(struct watchdog_device *wdev)
{
        struct msc313e_wdt_priv *priv = watchdog_get_drvdata(wdev);

        writew(1, priv->base + REG_WDT_CLR);
        return 0;
}

static int msc313e_wdt_stop(struct watchdog_device *wdev)
{
        struct msc313e_wdt_priv *priv = watchdog_get_drvdata(wdev);

        writew(0, priv->base + REG_WDT_MAX_PRD_L);
        writew(0, priv->base + REG_WDT_MAX_PRD_H);
        writew(0, priv->base + REG_WDT_CLR);
        clk_disable_unprepare(priv->clk);
        return 0;
}

static int msc313e_wdt_settimeout(struct watchdog_device *wdev, unsigned int new_time)
{
        wdev->timeout = new_time;

        return msc313e_wdt_start(wdev);
}

static const struct watchdog_info msc313e_wdt_ident = {
        .identity = "MSC313e watchdog",
        .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
};

static const struct watchdog_ops msc313e_wdt_ops = {
        .owner = THIS_MODULE,
        .start = msc313e_wdt_start,
        .stop = msc313e_wdt_stop,
        .ping = msc313e_wdt_ping,
        .set_timeout = msc313e_wdt_settimeout,
};

static const struct of_device_id msc313e_wdt_of_match[] = {
        { .compatible = "mstar,msc313e-wdt", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, msc313e_wdt_of_match);

static int msc313e_wdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct msc313e_wdt_priv *priv;

        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(priv->base))
                return PTR_ERR(priv->base);

        priv->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(priv->clk)) {
                dev_err(dev, "No input clock\n");
                return PTR_ERR(priv->clk);
        }

        priv->wdev.info = &msc313e_wdt_ident,
        priv->wdev.ops = &msc313e_wdt_ops,
        priv->wdev.parent = dev;
        priv->wdev.min_timeout = MSC313E_WDT_MIN_TIMEOUT;
        priv->wdev.max_timeout = U32_MAX / clk_get_rate(priv->clk);
        priv->wdev.timeout = MSC313E_WDT_DEFAULT_TIMEOUT;

        /* If the period is non-zero the WDT is running */
        if (readw(priv->base + REG_WDT_MAX_PRD_L) | (readw(priv->base + REG_WDT_MAX_PRD_H) << 16))
                set_bit(WDOG_HW_RUNNING, &priv->wdev.status);

        watchdog_set_drvdata(&priv->wdev, priv);

        watchdog_init_timeout(&priv->wdev, timeout, dev);
        watchdog_stop_on_reboot(&priv->wdev);
        watchdog_stop_on_unregister(&priv->wdev);

        return devm_watchdog_register_device(dev, &priv->wdev);
}

static int __maybe_unused msc313e_wdt_suspend(struct device *dev)
{
        struct msc313e_wdt_priv *priv = dev_get_drvdata(dev);

        if (watchdog_active(&priv->wdev))
                msc313e_wdt_stop(&priv->wdev);

        return 0;
}

static int __maybe_unused msc313e_wdt_resume(struct device *dev)
{
        struct msc313e_wdt_priv *priv = dev_get_drvdata(dev);

        if (watchdog_active(&priv->wdev))
                msc313e_wdt_start(&priv->wdev);

        return 0;
}

static SIMPLE_DEV_PM_OPS(msc313e_wdt_pm_ops, msc313e_wdt_suspend, msc313e_wdt_resume);

static struct platform_driver msc313e_wdt_driver = {
        .driver = {
                .name = "msc313e-wdt",
                .of_match_table = msc313e_wdt_of_match,
                .pm = &msc313e_wdt_pm_ops,
        },
        .probe = msc313e_wdt_probe,
};
module_platform_driver(msc313e_wdt_driver);

MODULE_AUTHOR("Daniel Palmer <daniel@thingy.jp>");
MODULE_DESCRIPTION("Watchdog driver for MStar MSC313e");
MODULE_LICENSE("GPL v2");