// SPDX-License-Identifier: GPL-2.0-only
/*
 * MOXA ART SoCs watchdog driver.
 *
 * Copyright (C) 2013 Jonas Jensen
 *
 * Jonas Jensen <jonas.jensen@gmail.com>
 *
 */

#include <linux/clk.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#include <linux/moduleparam.h>

#define REG_COUNT                       0x4
#define REG_MODE                        0x8
#define REG_ENABLE                      0xC

struct moxart_wdt_dev {
        struct watchdog_device dev;
        void __iomem *base;
        unsigned int clock_frequency;
};

static int heartbeat;

static int moxart_wdt_restart(struct watchdog_device *wdt_dev,
                              unsigned long action, void *data)
{
        struct moxart_wdt_dev *moxart_wdt = watchdog_get_drvdata(wdt_dev);

        writel(1, moxart_wdt->base + REG_COUNT);
        writel(0x5ab9, moxart_wdt->base + REG_MODE);
        writel(0x03, moxart_wdt->base + REG_ENABLE);

        return 0;
}

static int moxart_wdt_stop(struct watchdog_device *wdt_dev)
{
        struct moxart_wdt_dev *moxart_wdt = watchdog_get_drvdata(wdt_dev);

        writel(0, moxart_wdt->base + REG_ENABLE);

        return 0;
}

static int moxart_wdt_start(struct watchdog_device *wdt_dev)
{
        struct moxart_wdt_dev *moxart_wdt = watchdog_get_drvdata(wdt_dev);

        writel(moxart_wdt->clock_frequency * wdt_dev->timeout,
               moxart_wdt->base + REG_COUNT);
        writel(0x5ab9, moxart_wdt->base + REG_MODE);
        writel(0x03, moxart_wdt->base + REG_ENABLE);

        return 0;
}

static int moxart_wdt_set_timeout(struct watchdog_device *wdt_dev,
                                  unsigned int timeout)
{
        wdt_dev->timeout = timeout;

        return 0;
}

static const struct watchdog_info moxart_wdt_info = {
        .identity       = "moxart-wdt",
        .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
                          WDIOF_MAGICCLOSE,
};

static const struct watchdog_ops moxart_wdt_ops = {
        .owner          = THIS_MODULE,
        .start          = moxart_wdt_start,
        .stop           = moxart_wdt_stop,
        .set_timeout    = moxart_wdt_set_timeout,
        .restart        = moxart_wdt_restart,
};

static int moxart_wdt_probe(struct platform_device *pdev)
{
        struct moxart_wdt_dev *moxart_wdt;
        struct device *dev = &pdev->dev;
        struct clk *clk;
        int err;
        unsigned int max_timeout;
        bool nowayout = WATCHDOG_NOWAYOUT;

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

        platform_set_drvdata(pdev, moxart_wdt);

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

        clk = devm_clk_get(dev, NULL);
        if (IS_ERR(clk)) {
                pr_err("%s: of_clk_get failed\n", __func__);
                return PTR_ERR(clk);
        }

        moxart_wdt->clock_frequency = clk_get_rate(clk);
        if (moxart_wdt->clock_frequency == 0) {
                pr_err("%s: incorrect clock frequency\n", __func__);
                return -EINVAL;
        }

        max_timeout = UINT_MAX / moxart_wdt->clock_frequency;

        moxart_wdt->dev.info = &moxart_wdt_info;
        moxart_wdt->dev.ops = &moxart_wdt_ops;
        moxart_wdt->dev.timeout = max_timeout;
        moxart_wdt->dev.min_timeout = 1;
        moxart_wdt->dev.max_timeout = max_timeout;
        moxart_wdt->dev.parent = dev;

        watchdog_init_timeout(&moxart_wdt->dev, heartbeat, dev);
        watchdog_set_nowayout(&moxart_wdt->dev, nowayout);
        watchdog_set_restart_priority(&moxart_wdt->dev, 128);

        watchdog_set_drvdata(&moxart_wdt->dev, moxart_wdt);

        watchdog_stop_on_unregister(&moxart_wdt->dev);
        err = devm_watchdog_register_device(dev, &moxart_wdt->dev);
        if (err)
                return err;

        dev_dbg(dev, "Watchdog enabled (heartbeat=%d sec, nowayout=%d)\n",
                moxart_wdt->dev.timeout, nowayout);

        return 0;
}

static const struct of_device_id moxart_watchdog_match[] = {
        { .compatible = "moxa,moxart-watchdog" },
        { },
};
MODULE_DEVICE_TABLE(of, moxart_watchdog_match);

static struct platform_driver moxart_wdt_driver = {
        .probe      = moxart_wdt_probe,
        .driver     = {
                .name           = "moxart-watchdog",
                .of_match_table = moxart_watchdog_match,
        },
};
module_platform_driver(moxart_wdt_driver);

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

MODULE_DESCRIPTION("MOXART watchdog driver");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jonas Jensen <jonas.jensen@gmail.com>");