/*
   *	60xx Single Board Computer Watchdog Timer driver for Linux 2.2.x
   *
   *	Based on acquirewdt.c by Alan Cox.
   *
   *	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.
   *
   *	The author does NOT admit liability nor provide warranty for
   *	any of this software. This material is provided "AS-IS" in
   *	the hope that it may be useful for others.
   *
   *	(c) Copyright 2000    Jakob Oestergaard <jakob@unthought.net>
   *
   *           12/4 - 2000      [Initial revision]
   *           25/4 - 2000      Added /dev/watchdog support
   *           09/5 - 2001      [smj@oro.net] fixed fop_write to "return 1"
   *					on success
   *           12/4 - 2002      [rob@osinvestor.com] eliminate fop_read
   *                            fix possible wdt_is_open race
   *                            add CONFIG_WATCHDOG_NOWAYOUT support
   *                            remove lock_kernel/unlock_kernel pairs
   *                            added KERN_* to printk's
   *                            got rid of extraneous comments
   *                            changed watchdog_info to correctly reflect what
   *			      the driver offers
   *			      added WDIOC_GETSTATUS, WDIOC_GETBOOTSTATUS,
   *			      WDIOC_SETTIMEOUT, WDIOC_GETTIMEOUT, and
   *			      WDIOC_SETOPTIONS ioctls
   *           09/8 - 2003      [wim@iguana.be] cleanup of trailing spaces
   *                            use module_param
   *                            made timeout (the emulated heartbeat) a
   *			      module_param
   *                            made the keepalive ping an internal subroutine
   *                            made wdt_stop and wdt_start module params
   *                            added extra printk's for startup problems
   *                            added MODULE_AUTHOR and MODULE_DESCRIPTION info
   *
   *
   *  This WDT driver is different from the other Linux WDT
   *  drivers in the following ways:
   *  *)  The driver will ping the watchdog by itself, because this
   *      particular WDT has a very short timeout (one second) and it
   *      would be insane to count on any userspace daemon always
   *      getting scheduled within that time frame.
   *
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/types.h>
  #include <linux/timer.h>
  #include <linux/jiffies.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>
  
  
  #define OUR_NAME "sbc60xxwdt"
  #define PFX OUR_NAME ": "
  
  /*
   * You must set these - The driver cannot probe for the settings
   */
  
  static int wdt_stop = 0x45;
  module_param(wdt_stop, int, 0);
  MODULE_PARM_DESC(wdt_stop, "SBC60xx WDT 'stop' io port (default 0x45)");
  
  static int wdt_start = 0x443;
  module_param(wdt_start, int, 0);
  MODULE_PARM_DESC(wdt_start, "SBC60xx WDT 'start' io port (default 0x443)");
  
  /*
   * The 60xx board can use watchdog timeout values from one second
   * to several minutes.  The default is one second, so if we reset
   * the watchdog every ~250ms we should be safe.
   */
  
  #define WDT_INTERVAL (HZ/4+1)
  
  /*
   * We must not require too good response from the userspace daemon.
   * Here we require the userspace daemon to send us a heartbeat
   * char to /dev/watchdog every 30 seconds.
   * If the daemon pulses us every 25 seconds, we can still afford
   * a 5 second scheduling delay on the (high priority) daemon. That
   * should be sufficient for a box under any load.
   */
  
  #define WATCHDOG_TIMEOUT 30		/* 30 sec default timeout */
  static int timeout = WATCHDOG_TIMEOUT;	/* in seconds, multiplied by HZ to
  					   get seconds to wait for a ping */
  module_param(timeout, int, 0);
  MODULE_PARM_DESC(timeout,
  	"Watchdog timeout in seconds. (1<=timeout<=3600, default="
  				__MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  
  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 wdt_timer_ping(unsigned long);
  static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
  static unsigned long next_heartbeat;
  static unsigned long wdt_is_open;
  static char wdt_expect_close;
  
  /*
   *	Whack the dog
   */
  
  static void wdt_timer_ping(unsigned long data)
  {
  	/* If we got a heartbeat pulse within the WDT_US_INTERVAL
  	 * we agree to ping the WDT
  	 */
  	if (time_before(jiffies, next_heartbeat)) {
  		/* Ping the WDT by reading from wdt_start */
  		inb_p(wdt_start);
  		/* Re-set the timer interval */
  		mod_timer(&timer, jiffies + WDT_INTERVAL);
  	} else
  		pr_warn("Heartbeat lost! Will not ping the watchdog
  ");
  }
  
  /*
   * Utility routines
   */
  
  static void wdt_startup(void)
  {
  	next_heartbeat = jiffies + (timeout * HZ);
  
  	/* Start the timer */
  	mod_timer(&timer, jiffies + WDT_INTERVAL);
  	pr_info("Watchdog timer is now enabled
  ");
  }
  
  static void wdt_turnoff(void)
  {
  	/* Stop the timer */
  	del_timer(&timer);
  	inb_p(wdt_stop);
  	pr_info("Watchdog timer is now disabled...
  ");
  }
  
  static void wdt_keepalive(void)
  {
  	/* user land ping */
  	next_heartbeat = jiffies + (timeout * HZ);
  }
  
  /*
   * /dev/watchdog handling
   */
  
  static ssize_t fop_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 ofs;
  
  			/* note: just in case someone wrote the
  			   magic character five months ago... */
  			wdt_expect_close = 0;
  
  			/* scan to see whether or not we got the
  			   magic character */
  			for (ofs = 0; ofs != count; ofs++) {
  				char c;
  				if (get_user(c, buf + ofs))
  					return -EFAULT;
  				if (c == 'V')
  					wdt_expect_close = 42;
  			}
  		}
  
  		/* Well, anyhow someone wrote to us, we should
  		   return that favour */
  		wdt_keepalive();
  	}
  	return count;
  }
  
  static int fop_open(struct inode *inode, struct file *file)
  {
  	/* Just in case we're already talking to someone... */
  	if (test_and_set_bit(0, &wdt_is_open))
  		return -EBUSY;
  
  	if (nowayout)
  		__module_get(THIS_MODULE);
  
  	/* Good, fire up the show */
  	wdt_startup();
  	return nonseekable_open(inode, file);
  }
  
  static int fop_close(struct inode *inode, struct file *file)
  {
  	if (wdt_expect_close == 42)
  		wdt_turnoff();
  	else {
  		del_timer(&timer);
  		pr_crit("device file closed unexpectedly. Will not stop the WDT!
  ");
  	}
  	clear_bit(0, &wdt_is_open);
  	wdt_expect_close = 0;
  	return 0;
  }
  
  static long fop_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 = "SBC60xx",
  	};
  
  	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:
  	{
  		int new_options, retval = -EINVAL;
  		if (get_user(new_options, p))
  			return -EFAULT;
  		if (new_options & WDIOS_DISABLECARD) {
  			wdt_turnoff();
  			retval = 0;
  		}
  		if (new_options & WDIOS_ENABLECARD) {
  			wdt_startup();
  			retval = 0;
  		}
  		return retval;
  	}
  	case WDIOC_KEEPALIVE:
  		wdt_keepalive();
  		return 0;
  	case WDIOC_SETTIMEOUT:
  	{
  		int new_timeout;
  		if (get_user(new_timeout, p))
  			return -EFAULT;
  		/* arbitrary upper limit */
  		if (new_timeout < 1 || new_timeout > 3600)
  			return -EINVAL;
  
  		timeout = new_timeout;
  		wdt_keepalive();
  		/* Fall through */
  	}
  	case WDIOC_GETTIMEOUT:
  		return put_user(timeout, p);
  	default:
  		return -ENOTTY;
  	}
  }
  
  static const struct file_operations wdt_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= fop_write,
  	.open		= fop_open,
  	.release	= fop_close,
  	.unlocked_ioctl	= fop_ioctl,
  };
  
  static struct miscdevice wdt_miscdev = {
  	.minor = WATCHDOG_MINOR,
  	.name = "watchdog",
  	.fops = &wdt_fops,
  };
  
  /*
   *	Notifier for system down
   */
  
  static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
  	void *unused)
  {
  	if (code == SYS_DOWN || code == SYS_HALT)
  		wdt_turnoff();
  	return NOTIFY_DONE;
  }
  
  /*
   *	The WDT needs to learn about soft shutdowns in order to
   *	turn the timebomb registers off.
   */
  
  static struct notifier_block wdt_notifier = {
  	.notifier_call = wdt_notify_sys,
  };
  
  static void __exit sbc60xxwdt_unload(void)
  {
  	wdt_turnoff();
  
  	/* Deregister */
  	misc_deregister(&wdt_miscdev);
  
  	unregister_reboot_notifier(&wdt_notifier);
  	if ((wdt_stop != 0x45) && (wdt_stop != wdt_start))
  		release_region(wdt_stop, 1);
  	release_region(wdt_start, 1);
  }
  
  static int __init sbc60xxwdt_init(void)
  {
  	int rc = -EBUSY;
  
  	if (timeout < 1 || timeout > 3600) { /* arbitrary upper limit */
  		timeout = WATCHDOG_TIMEOUT;
  		pr_info("timeout value must be 1 <= x <= 3600, using %d
  ",
  			timeout);
  	}
  
  	if (!request_region(wdt_start, 1, "SBC 60XX WDT")) {
  		pr_err("I/O address 0x%04x already in use
  ", wdt_start);
  		rc = -EIO;
  		goto err_out;
  	}
  
  	/* We cannot reserve 0x45 - the kernel already has! */
  	if (wdt_stop != 0x45 && wdt_stop != wdt_start) {
  		if (!request_region(wdt_stop, 1, "SBC 60XX WDT")) {
  			pr_err("I/O address 0x%04x already in use
  ", wdt_stop);
  			rc = -EIO;
  			goto err_out_region1;
  		}
  	}
  
  	rc = register_reboot_notifier(&wdt_notifier);
  	if (rc) {
  		pr_err("cannot register reboot notifier (err=%d)
  ", rc);
  		goto err_out_region2;
  	}
  
  	rc = misc_register(&wdt_miscdev);
  	if (rc) {
  		pr_err("cannot register miscdev on minor=%d (err=%d)
  ",
  		       wdt_miscdev.minor, rc);
  		goto err_out_reboot;
  	}
  	pr_info("WDT driver for 60XX single board computer initialised. timeout=%d sec (nowayout=%d)
  ",
  		timeout, nowayout);
  
  	return 0;
  
  err_out_reboot:
  	unregister_reboot_notifier(&wdt_notifier);
  err_out_region2:
  	if (wdt_stop != 0x45 && wdt_stop != wdt_start)
  		release_region(wdt_stop, 1);
  err_out_region1:
  	release_region(wdt_start, 1);
  err_out:
  	return rc;
  }
  
  module_init(sbc60xxwdt_init);
  module_exit(sbc60xxwdt_unload);
  
  MODULE_AUTHOR("Jakob Oestergaard <jakob@unthought.net>");
  MODULE_DESCRIPTION("60xx Single Board Computer Watchdog Timer driver");
  MODULE_LICENSE("GPL");