/*
   *	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 */
  	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!
  ");
  		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
  ");
  
  	if (timeout < 1 || timeout > 255) {
  		timeout = WD_TIMO;
  		pr_info("timeout value must be 1 <= x <= 255, using %d
  ",
  			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
  ", 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
  ", wdt_start);
  		ret = -EIO;
  		goto error2;
  	}
  
  	ret = register_reboot_notifier(&wafwdt_notifier);
  	if (ret != 0) {
  		pr_err("cannot register reboot notifier (err=%d)
  ", ret);
  		goto error3;
  	}
  
  	ret = misc_register(&wafwdt_miscdev);
  	if (ret != 0) {
  		pr_err("cannot register miscdev on minor=%d (err=%d)
  ",
  		       WATCHDOG_MINOR, ret);
  		goto error4;
  	}
  
  	pr_info("initialized. timeout=%d sec (nowayout=%d)
  ",
  		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 */