// SPDX-License-Identifier: GPL-2.0+
/*
 *      Eurotech CPU-1220/1410/1420 on board WDT driver
 *
 *      (c) Copyright 2001 Ascensit <support@ascensit.com>
 *      (c) Copyright 2001 Rodolfo Giometti <giometti@ascensit.com>
 *      (c) Copyright 2002 Rob Radez <rob@osinvestor.com>
 *
 *      Based on wdt.c.
 *      Original copyright messages:
 *
 *      (c) Copyright 1996-1997 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 *
 *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *      warranty for any of this software. This material is provided
 *      "AS-IS" and at no charge.
 *
 *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>*
 */

/* Changelog:
 *
 * 2001 - Rodolfo Giometti
 *      Initial release
 *
 * 2002/04/25 - Rob Radez
 *      clean up #includes
 *      clean up locking
 *      make __setup param unique
 *      proper options in watchdog_info
 *      add WDIOC_GETSTATUS and WDIOC_SETOPTIONS ioctls
 *      add expect_close support
 *
 * 2002.05.30 - Joel Becker <joel.becker@oracle.com>
 *      Added Matt Domsch's nowayout module option.
 */

/*
 *      The eurotech CPU-1220/1410/1420's watchdog is a part
 *      of the on-board SUPER I/O device SMSC FDC 37B782.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/uaccess.h>


static unsigned long eurwdt_is_open;
static int eurwdt_timeout;
static char eur_expect_close;
static DEFINE_SPINLOCK(eurwdt_lock);

/*
 * You must set these - there is no sane way to probe for this board.
 */

static int io = 0x3f0;
static int irq = 10;
static char *ev = "int";

#define WDT_TIMEOUT             60                /* 1 minute */

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
                "Watchdog cannot be stopped once started (default="
                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

/*
 * Some symbolic names
 */

#define WDT_CTRL_REG            0x30
#define WDT_OUTPIN_CFG          0xe2
#define WDT_EVENT_INT           0x00
#define WDT_EVENT_REBOOT        0x08
#define WDT_UNIT_SEL            0xf1
#define WDT_UNIT_SECS           0x80
#define WDT_TIMEOUT_VAL         0xf2
#define WDT_TIMER_CFG           0xf3


module_param_hw(io, int, ioport, 0);
MODULE_PARM_DESC(io, "Eurotech WDT io port (default=0x3f0)");
module_param_hw(irq, int, irq, 0);
MODULE_PARM_DESC(irq, "Eurotech WDT irq (default=10)");
module_param(ev, charp, 0);
MODULE_PARM_DESC(ev, "Eurotech WDT event type (default is `int')");


/*
 * Programming support
 */

static inline void eurwdt_write_reg(u8 index, u8 data)
{
        outb(index, io);
        outb(data, io+1);
}

static inline void eurwdt_lock_chip(void)
{
        outb(0xaa, io);
}

static inline void eurwdt_unlock_chip(void)
{
        outb(0x55, io);
        eurwdt_write_reg(0x07, 0x08);   /* set the logical device */
}

static inline void eurwdt_set_timeout(int timeout)
{
        eurwdt_write_reg(WDT_TIMEOUT_VAL, (u8) timeout);
}

static inline void eurwdt_disable_timer(void)
{
        eurwdt_set_timeout(0);
}

static void eurwdt_activate_timer(void)
{
        eurwdt_disable_timer();
        eurwdt_write_reg(WDT_CTRL_REG, 0x01);   /* activate the WDT */
        eurwdt_write_reg(WDT_OUTPIN_CFG,
                !strcmp("int", ev) ? WDT_EVENT_INT : WDT_EVENT_REBOOT);

        /* Setting interrupt line */
        if (irq == 2 || irq > 15 || irq < 0) {
                pr_err("invalid irq number\n");
                irq = 0;        /* if invalid we disable interrupt */
        }
        if (irq == 0)
                pr_info("interrupt disabled\n");

        eurwdt_write_reg(WDT_TIMER_CFG, irq << 4);

        eurwdt_write_reg(WDT_UNIT_SEL, WDT_UNIT_SECS);  /* we use seconds */
        eurwdt_set_timeout(0);  /* the default timeout */
}


/*
 * Kernel methods.
 */

static irqreturn_t eurwdt_interrupt(int irq, void *dev_id)
{
        pr_crit("timeout WDT timeout\n");

#ifdef ONLY_TESTING
        pr_crit("Would Reboot\n");
#else
        pr_crit("Initiating system reboot\n");
        emergency_restart();
#endif
        return IRQ_HANDLED;
}


/**
 * eurwdt_ping:
 *
 * Reload counter one with the watchdog timeout.
 */

static void eurwdt_ping(void)
{
        /* Write the watchdog default value */
        eurwdt_set_timeout(eurwdt_timeout);
}

/**
 * eurwdt_write:
 * @file: file handle to the watchdog
 * @buf: buffer to write (unused as data does not matter here
 * @count: count of bytes
 * @ppos: pointer to the position to write. No seeks allowed
 *
 * A write to a watchdog device is defined as a keepalive signal. Any
 * write of data will do, as we we don't define content meaning.
 */

static ssize_t eurwdt_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
        if (count) {
                if (!nowayout) {
                        size_t i;

                        eur_expect_close = 0;

                        for (i = 0; i != count; i++) {
                                char c;
                                if (get_user(c, buf + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        eur_expect_close = 42;
                        }
                }
                spin_lock(&eurwdt_lock);
                eurwdt_ping();  /* the default timeout */
                spin_unlock(&eurwdt_lock);
        }
        return count;
}

/**
 * eurwdt_ioctl:
 * @file: file handle to the device
 * @cmd: watchdog command
 * @arg: argument pointer
 *
 * The watchdog API defines a common set of functions for all watchdogs
 * according to their available features.
 */

static long eurwdt_ioctl(struct file *file,
                                        unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        static const struct watchdog_info ident = {
                .options          = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
                                                        | WDIOF_MAGICCLOSE,
                .firmware_version = 1,
                .identity         = "WDT Eurotech CPU-1220/1410",
        };

        int time;
        int options, retval = -EINVAL;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;

        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);

        case WDIOC_SETOPTIONS:
                if (get_user(options, p))
                        return -EFAULT;
                spin_lock(&eurwdt_lock);
                if (options & WDIOS_DISABLECARD) {
                        eurwdt_disable_timer();
                        retval = 0;
                }
                if (options & WDIOS_ENABLECARD) {
                        eurwdt_activate_timer();
                        eurwdt_ping();
                        retval = 0;
                }
                spin_unlock(&eurwdt_lock);
                return retval;

        case WDIOC_KEEPALIVE:
                spin_lock(&eurwdt_lock);
                eurwdt_ping();
                spin_unlock(&eurwdt_lock);
                return 0;

        case WDIOC_SETTIMEOUT:
                if (copy_from_user(&time, p, sizeof(int)))
                        return -EFAULT;

                /* Sanity check */
                if (time < 0 || time > 255)
                        return -EINVAL;

                spin_lock(&eurwdt_lock);
                eurwdt_timeout = time;
                eurwdt_set_timeout(time);
                spin_unlock(&eurwdt_lock);
                fallthrough;

        case WDIOC_GETTIMEOUT:
                return put_user(eurwdt_timeout, p);

        default:
                return -ENOTTY;
        }
}

/**
 * eurwdt_open:
 * @inode: inode of device
 * @file: file handle to device
 *
 * The misc device has been opened. The watchdog device is single
 * open and on opening we load the counter.
 */

static int eurwdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &eurwdt_is_open))
                return -EBUSY;
        eurwdt_timeout = WDT_TIMEOUT;   /* initial timeout */
        /* Activate the WDT */
        eurwdt_activate_timer();
        return stream_open(inode, file);
}

/**
 * eurwdt_release:
 * @inode: inode to board
 * @file: file handle to board
 *
 * The watchdog has a configurable API. There is a religious dispute
 * between people who want their watchdog to be able to shut down and
 * those who want to be sure if the watchdog manager dies the machine
 * reboots. In the former case we disable the counters, in the latter
 * case you have to open it again very soon.
 */

static int eurwdt_release(struct inode *inode, struct file *file)
{
        if (eur_expect_close == 42)
                eurwdt_disable_timer();
        else {
                pr_crit("Unexpected close, not stopping watchdog!\n");
                eurwdt_ping();
        }
        clear_bit(0, &eurwdt_is_open);
        eur_expect_close = 0;
        return 0;
}

/**
 * eurwdt_notify_sys:
 * @this: our notifier block
 * @code: the event being reported
 * @unused: unused
 *
 * Our notifier is called on system shutdowns. We want to turn the card
 * off at reboot otherwise the machine will reboot again during memory
 * test or worse yet during the following fsck. This would suck, in fact
 * trust me - if it happens it does suck.
 */

static int eurwdt_notify_sys(struct notifier_block *this, unsigned long code,
        void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                eurwdt_disable_timer(); /* Turn the card off */

        return NOTIFY_DONE;
}

/*
 * Kernel Interfaces
 */


static const struct file_operations eurwdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = eurwdt_write,
        .unlocked_ioctl = eurwdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = eurwdt_open,
        .release        = eurwdt_release,
};

static struct miscdevice eurwdt_miscdev = {
        .minor  = WATCHDOG_MINOR,
        .name   = "watchdog",
        .fops   = &eurwdt_fops,
};

/*
 * The WDT card needs to learn about soft shutdowns in order to
 * turn the timebomb registers off.
 */

static struct notifier_block eurwdt_notifier = {
        .notifier_call = eurwdt_notify_sys,
};

/**
 * eurwdt_exit:
 *
 * Unload the watchdog. You cannot do this with any file handles open.
 * If your watchdog is set to continue ticking on close and you unload
 * it, well it keeps ticking. We won't get the interrupt but the board
 * will not touch PC memory so all is fine. You just have to load a new
 * module in 60 seconds or reboot.
 */

static void __exit eurwdt_exit(void)
{
        eurwdt_lock_chip();

        misc_deregister(&eurwdt_miscdev);

        unregister_reboot_notifier(&eurwdt_notifier);
        release_region(io, 2);
        free_irq(irq, NULL);
}

/**
 * eurwdt_init:
 *
 * Set up the WDT watchdog board. After grabbing the resources
 * we require we need also to unlock the device.
 * The open() function will actually kick the board off.
 */

static int __init eurwdt_init(void)
{
        int ret;

        ret = request_irq(irq, eurwdt_interrupt, 0, "eurwdt", NULL);
        if (ret) {
                pr_err("IRQ %d is not free\n", irq);
                goto out;
        }

        if (!request_region(io, 2, "eurwdt")) {
                pr_err("IO %X is not free\n", io);
                ret = -EBUSY;
                goto outirq;
        }

        ret = register_reboot_notifier(&eurwdt_notifier);
        if (ret) {
                pr_err("can't register reboot notifier (err=%d)\n", ret);
                goto outreg;
        }

        ret = misc_register(&eurwdt_miscdev);
        if (ret) {
                pr_err("can't misc_register on minor=%d\n", WATCHDOG_MINOR);
                goto outreboot;
        }

        eurwdt_unlock_chip();

        ret = 0;
        pr_info("Eurotech WDT driver 0.01 at %X (Interrupt %d) - timeout event: %s\n",
                io, irq, (!strcmp("int", ev) ? "int" : "reboot"));

out:
        return ret;

outreboot:
        unregister_reboot_notifier(&eurwdt_notifier);

outreg:
        release_region(io, 2);

outirq:
        free_irq(irq, NULL);
        goto out;
}

module_init(eurwdt_init);
module_exit(eurwdt_exit);

MODULE_AUTHOR("Rodolfo Giometti");
MODULE_DESCRIPTION("Driver for Eurotech CPU-1220/1410 on board watchdog");
MODULE_LICENSE("GPL");