// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      sun4v watchdog timer
 *      (c) Copyright 2016 Oracle Corporation
 *
 *      Implement a simple watchdog driver using the built-in sun4v hypervisor
 *      watchdog support. If time expires, the hypervisor stops or bounces
 *      the guest domain.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/watchdog.h>
#include <asm/hypervisor.h>
#include <asm/mdesc.h>

#define WDT_TIMEOUT                     60
#define WDT_MAX_TIMEOUT                 31536000
#define WDT_MIN_TIMEOUT                 1
#define WDT_DEFAULT_RESOLUTION_MS       1000    /* 1 second */

static unsigned int timeout;
module_param(timeout, uint, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
        __MODULE_STRING(WDT_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 int sun4v_wdt_stop(struct watchdog_device *wdd)
{
        sun4v_mach_set_watchdog(0, NULL);

        return 0;
}

static int sun4v_wdt_ping(struct watchdog_device *wdd)
{
        int hverr;

        /*
         * HV watchdog timer will round up the timeout
         * passed in to the nearest multiple of the
         * watchdog resolution in milliseconds.
         */
        hverr = sun4v_mach_set_watchdog(wdd->timeout * 1000, NULL);
        if (hverr == HV_EINVAL)
                return -EINVAL;

        return 0;
}

static int sun4v_wdt_set_timeout(struct watchdog_device *wdd,
                                 unsigned int timeout)
{
        wdd->timeout = timeout;

        return 0;
}

static const struct watchdog_info sun4v_wdt_ident = {
        .options =      WDIOF_SETTIMEOUT |
                        WDIOF_MAGICCLOSE |
                        WDIOF_KEEPALIVEPING,
        .identity =     "sun4v hypervisor watchdog",
        .firmware_version = 0,
};

static const struct watchdog_ops sun4v_wdt_ops = {
        .owner =        THIS_MODULE,
        .start =        sun4v_wdt_ping,
        .stop =         sun4v_wdt_stop,
        .ping =         sun4v_wdt_ping,
        .set_timeout =  sun4v_wdt_set_timeout,
};

static struct watchdog_device wdd = {
        .info = &sun4v_wdt_ident,
        .ops = &sun4v_wdt_ops,
        .min_timeout = WDT_MIN_TIMEOUT,
        .max_timeout = WDT_MAX_TIMEOUT,
        .timeout = WDT_TIMEOUT,
};

static int __init sun4v_wdt_init(void)
{
        struct mdesc_handle *handle;
        u64 node;
        const u64 *value;
        int err = 0;
        unsigned long major = 1, minor = 1;

        /*
         * There are 2 properties that can be set from the control
         * domain for the watchdog.
         * watchdog-resolution
         * watchdog-max-timeout
         *
         * We can expect a handle to be returned otherwise something
         * serious is wrong. Correct to return -ENODEV here.
         */

        handle = mdesc_grab();
        if (!handle)
                return -ENODEV;

        node = mdesc_node_by_name(handle, MDESC_NODE_NULL, "platform");
        err = -ENODEV;
        if (node == MDESC_NODE_NULL)
                goto out_release;

        /*
         * This is a safe way to validate if we are on the right
         * platform.
         */
        if (sun4v_hvapi_register(HV_GRP_CORE, major, &minor))
                goto out_hv_unreg;

        /* Allow value of watchdog-resolution up to 1s (default) */
        value = mdesc_get_property(handle, node, "watchdog-resolution", NULL);
        err = -EINVAL;
        if (value) {
                if (*value == 0 ||
                    *value > WDT_DEFAULT_RESOLUTION_MS)
                        goto out_hv_unreg;
        }

        value = mdesc_get_property(handle, node, "watchdog-max-timeout", NULL);
        if (value) {
                /*
                 * If the property value (in ms) is smaller than
                 * min_timeout, return -EINVAL.
                 */
                if (*value < wdd.min_timeout * 1000)
                        goto out_hv_unreg;

                /*
                 * If the property value is smaller than
                 * default max_timeout  then set watchdog max_timeout to
                 * the value of the property in seconds.
                 */
                if (*value < wdd.max_timeout * 1000)
                        wdd.max_timeout = *value  / 1000;
        }

        watchdog_init_timeout(&wdd, timeout, NULL);

        watchdog_set_nowayout(&wdd, nowayout);

        err = watchdog_register_device(&wdd);
        if (err)
                goto out_hv_unreg;

        pr_info("initialized (timeout=%ds, nowayout=%d)\n",
                 wdd.timeout, nowayout);

        mdesc_release(handle);

        return 0;

out_hv_unreg:
        sun4v_hvapi_unregister(HV_GRP_CORE);

out_release:
        mdesc_release(handle);
        return err;
}

static void __exit sun4v_wdt_exit(void)
{
        sun4v_hvapi_unregister(HV_GRP_CORE);
        watchdog_unregister_device(&wdd);
}

module_init(sun4v_wdt_init);
module_exit(sun4v_wdt_exit);

MODULE_AUTHOR("Wim Coekaerts <wim.coekaerts@oracle.com>");
MODULE_DESCRIPTION("sun4v watchdog driver");
MODULE_LICENSE("GPL");