/*
 *      ICP Wafer 5823 Single Board Computer WDT driver
 *      http://www.icpamerica.com/wafer_5823.php
 *      May also work on other similar models
 *
 *      (c) Copyright 2002 Justin Cormack <justin@street-vision.com>
 *
 *      Release 0.02
 *
 *      Based on advantechwdt.c which is based on wdt.c.
 *      Original copyright messages:
 *
 *      (c) Copyright 1996-1997 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 *      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>
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.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/spinlock.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#define WATCHDOG_NAME "Wafer 5823 WDT"
#define PFX WATCHDOG_NAME ": "
#define WD_TIMO 60                      /* 60 sec default timeout */

static unsigned long wafwdt_is_open;
static char expect_close;
static DEFINE_SPINLOCK(wafwdt_lock);

/*
 *      You must set these - there is no sane way to probe for this board.
 *
 *      To enable, write the timeout value in seconds (1 to 255) to I/O
 *      port WDT_START, then read the port to start the watchdog. To pat
 *      the dog, read port WDT_STOP to stop the timer, then read WDT_START
 *      to restart it again.
 */

static int wdt_stop = 0x843;
static int wdt_start = 0x443;

static int timeout = WD_TIMO;  /* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
                "Watchdog timeout in seconds. 1 <= timeout <= 255, default="
                                __MODULE_STRING(WD_TIMO) ".");

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) ")");

static void wafwdt_ping(void)
{
        /* pat watchdog */
        spin_lock(&wafwdt_lock);
        inb_p(wdt_stop);
        inb_p(wdt_start);
        spin_unlock(&wafwdt_lock);
}

static void wafwdt_start(void)
{
        /* start up watchdog */
        outb_p(timeout, wdt_start);
        inb_p(wdt_start);
}

static void wafwdt_stop(void)
{
        /* stop watchdog */
        inb_p(wdt_stop);
}

static ssize_t wafwdt_write(struct file *file, const char __user *buf,
                                                size_t count, loff_t *ppos)
{
        /* See if we got the magic character 'V' and reload the timer */
        if (count) {
                if (!nowayout) {
                        size_t i;

                        /* In case it was set long ago */
                        expect_close = 0;

                        /* scan to see whether or not we got the magic
                           character */
                        for (i = 0; i != count; i++) {
                                char c;
                                if (get_user(c, buf + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        expect_close = 42;
                        }
                }
                /* Well, anyhow someone wrote to us, we should
                   return that favour */
                wafwdt_ping();
        }
        return count;
}

static long wafwdt_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        int new_timeout;
        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 = "Wafer 5823 WDT",
        };

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

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

        case WDIOC_SETOPTIONS:
        {
                int options, retval = -EINVAL;

                if (get_user(options, p))
                        return -EFAULT;

                if (options & WDIOS_DISABLECARD) {
                        wafwdt_stop();
                        retval = 0;
                }

                if (options & WDIOS_ENABLECARD) {
                        wafwdt_start();
                        retval = 0;
                }

                return retval;
        }

        case WDIOC_KEEPALIVE:
                wafwdt_ping();
                break;

        case WDIOC_SETTIMEOUT:
                if (get_user(new_timeout, p))
                        return -EFAULT;
                if ((new_timeout < 1) || (new_timeout > 255))
                        return -EINVAL;
                timeout = new_timeout;
                wafwdt_stop();
                wafwdt_start();
                /* Fall through */
        case WDIOC_GETTIMEOUT:
                return put_user(timeout, p);

        default:
                return -ENOTTY;
        }
        return 0;
}

static int wafwdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &wafwdt_is_open))
                return -EBUSY;

        /*
         *      Activate
         */
        wafwdt_start();
        return nonseekable_open(inode, file);
}

static int wafwdt_close(struct inode *inode, struct file *file)
{
        if (expect_close == 42)
                wafwdt_stop();
        else {
                pr_crit("WDT device closed unexpectedly.  WDT will not stop!\n");
                wafwdt_ping();
        }
        clear_bit(0, &wafwdt_is_open);
        expect_close = 0;
        return 0;
}

/*
 *      Notifier for system down
 */

static int wafwdt_notify_sys(struct notifier_block *this, unsigned long code,
                                                                void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                wafwdt_stop();
        return NOTIFY_DONE;
}

/*
 *      Kernel Interfaces
 */

static const struct file_operations wafwdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = wafwdt_write,
        .unlocked_ioctl = wafwdt_ioctl,
        .open           = wafwdt_open,
        .release        = wafwdt_close,
};

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

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

static struct notifier_block wafwdt_notifier = {
        .notifier_call = wafwdt_notify_sys,
};

static int __init wafwdt_init(void)
{
        int ret;

        pr_info("WDT driver for Wafer 5823 single board computer initialising\n");

        if (timeout < 1 || timeout > 255) {
                timeout = WD_TIMO;
                pr_info("timeout value must be 1 <= x <= 255, using %d\n",
                        timeout);
        }

        if (wdt_stop != wdt_start) {
                if (!request_region(wdt_stop, 1, "Wafer 5823 WDT")) {
                        pr_err("I/O address 0x%04x already in use\n", wdt_stop);
                        ret = -EIO;
                        goto error;
                }
        }

        if (!request_region(wdt_start, 1, "Wafer 5823 WDT")) {
                pr_err("I/O address 0x%04x already in use\n", wdt_start);
                ret = -EIO;
                goto error2;
        }

        ret = register_reboot_notifier(&wafwdt_notifier);
        if (ret != 0) {
                pr_err("cannot register reboot notifier (err=%d)\n", ret);
                goto error3;
        }

        ret = misc_register(&wafwdt_miscdev);
        if (ret != 0) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, ret);
                goto error4;
        }

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

        return ret;
error4:
        unregister_reboot_notifier(&wafwdt_notifier);
error3:
        release_region(wdt_start, 1);
error2:
        if (wdt_stop != wdt_start)
                release_region(wdt_stop, 1);
error:
        return ret;
}

static void __exit wafwdt_exit(void)
{
        misc_deregister(&wafwdt_miscdev);
        unregister_reboot_notifier(&wafwdt_notifier);
        if (wdt_stop != wdt_start)
                release_region(wdt_stop, 1);
        release_region(wdt_start, 1);
}

module_init(wafwdt_init);
module_exit(wafwdt_exit);

MODULE_AUTHOR("Justin Cormack");
MODULE_DESCRIPTION("ICP Wafer 5823 Single Board Computer WDT driver");
MODULE_LICENSE("GPL");

/* end of wafer5823wdt.c */