// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Xen Watchdog Driver
 *
 *      (c) Copyright 2010 Novell, Inc.
 */

#define DRV_NAME        "xen_wdt"

#include <linux/bug.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/hrtimer.h>
#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#include <xen/xen.h>
#include <asm/xen/hypercall.h>
#include <xen/interface/sched.h>

static struct platform_device *platform_device;
static struct sched_watchdog wdt;
static time64_t wdt_expires;

#define WATCHDOG_TIMEOUT 60 /* in seconds */
static unsigned int timeout;
module_param(timeout, uint, S_IRUGO);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
        "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, S_IRUGO);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
        "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

static inline time64_t set_timeout(struct watchdog_device *wdd)
{
        wdt.timeout = wdd->timeout;
        return ktime_get_seconds() + wdd->timeout;
}

static int xen_wdt_start(struct watchdog_device *wdd)
{
        time64_t expires;
        int err;

        expires = set_timeout(wdd);
        if (!wdt.id)
                err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
        else
                err = -EBUSY;
        if (err > 0) {
                wdt.id = err;
                wdt_expires = expires;
                err = 0;
        } else
                BUG_ON(!err);

        return err;
}

static int xen_wdt_stop(struct watchdog_device *wdd)
{
        int err = 0;

        wdt.timeout = 0;
        if (wdt.id)
                err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
        if (!err)
                wdt.id = 0;

        return err;
}

static int xen_wdt_kick(struct watchdog_device *wdd)
{
        time64_t expires;
        int err;

        expires = set_timeout(wdd);
        if (wdt.id)
                err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
        else
                err = -ENXIO;
        if (!err)
                wdt_expires = expires;

        return err;
}

static unsigned int xen_wdt_get_timeleft(struct watchdog_device *wdd)
{
        return wdt_expires - ktime_get_seconds();
}

static struct watchdog_info xen_wdt_info = {
        .identity = DRV_NAME,
        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
};

static const struct watchdog_ops xen_wdt_ops = {
        .owner = THIS_MODULE,
        .start = xen_wdt_start,
        .stop = xen_wdt_stop,
        .ping = xen_wdt_kick,
        .get_timeleft = xen_wdt_get_timeleft,
};

static struct watchdog_device xen_wdt_dev = {
        .info = &xen_wdt_info,
        .ops = &xen_wdt_ops,
        .timeout = WATCHDOG_TIMEOUT,
};

static int xen_wdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct sched_watchdog wd = { .id = ~0 };
        int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);

        if (ret == -ENOSYS) {
                dev_err(dev, "watchdog not supported by hypervisor\n");
                return -ENODEV;
        }

        if (ret != -EINVAL) {
                dev_err(dev, "unexpected hypervisor error (%d)\n", ret);
                return -ENODEV;
        }

        watchdog_init_timeout(&xen_wdt_dev, timeout, NULL);
        watchdog_set_nowayout(&xen_wdt_dev, nowayout);
        watchdog_stop_on_reboot(&xen_wdt_dev);
        watchdog_stop_on_unregister(&xen_wdt_dev);

        ret = devm_watchdog_register_device(dev, &xen_wdt_dev);
        if (ret)
                return ret;

        dev_info(dev, "initialized (timeout=%ds, nowayout=%d)\n",
                 xen_wdt_dev.timeout, nowayout);

        return 0;
}

static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
{
        typeof(wdt.id) id = wdt.id;
        int rc = xen_wdt_stop(&xen_wdt_dev);

        wdt.id = id;
        return rc;
}

static int xen_wdt_resume(struct platform_device *dev)
{
        if (!wdt.id)
                return 0;
        wdt.id = 0;
        return xen_wdt_start(&xen_wdt_dev);
}

static struct platform_driver xen_wdt_driver = {
        .probe          = xen_wdt_probe,
        .suspend        = xen_wdt_suspend,
        .resume         = xen_wdt_resume,
        .driver         = {
                .name   = DRV_NAME,
        },
};

static int __init xen_wdt_init_module(void)
{
        int err;

        if (!xen_domain())
                return -ENODEV;

        err = platform_driver_register(&xen_wdt_driver);
        if (err)
                return err;

        platform_device = platform_device_register_simple(DRV_NAME,
                                                                  -1, NULL, 0);
        if (IS_ERR(platform_device)) {
                err = PTR_ERR(platform_device);
                platform_driver_unregister(&xen_wdt_driver);
        }

        return err;
}

static void __exit xen_wdt_cleanup_module(void)
{
        platform_device_unregister(platform_device);
        platform_driver_unregister(&xen_wdt_driver);
}

module_init(xen_wdt_init_module);
module_exit(xen_wdt_cleanup_module);

MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
MODULE_LICENSE("GPL");