/*
   *	NANO7240 SBC Watchdog device driver
   *
   *	Based on w83877f.c by Scott Jennings,
   *
   *	This program is free software; you can redistribute it and/or modify
   *	it under the terms of the GNU General Public License version 2 as
   *	published by the Free Software Foundation;
   *
   *	Software distributed under the License is distributed on an "AS IS"
   *	basis, WITHOUT WARRANTY OF ANY KIND, either express or
   *	implied. See the License for the specific language governing
   *	rights and limitations under the License.
   *
   *	(c) Copyright 2007  Gilles GIGAN <gilles.gigan@jcu.edu.au>
   *
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/fs.h>
  #include <linux/init.h>
  #include <linux/ioport.h>
  #include <linux/jiffies.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/miscdevice.h>
  #include <linux/notifier.h>
  #include <linux/reboot.h>
  #include <linux/types.h>
  #include <linux/watchdog.h>
  #include <linux/io.h>
  #include <linux/uaccess.h>
  #include <linux/atomic.h>
  
  #define SBC7240_ENABLE_PORT		0x443
  #define SBC7240_DISABLE_PORT		0x043
  #define SBC7240_SET_TIMEOUT_PORT	SBC7240_ENABLE_PORT
  #define SBC7240_MAGIC_CHAR		'V'
  
  #define SBC7240_TIMEOUT		30
  #define SBC7240_MAX_TIMEOUT		255
  static int timeout = SBC7240_TIMEOUT;	/* in seconds */
  module_param(timeout, int, 0);
  MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. (1<=timeout<="
  		 __MODULE_STRING(SBC7240_MAX_TIMEOUT) ", default="
  		 __MODULE_STRING(SBC7240_TIMEOUT) ")");
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout, "Disable watchdog when closing device file");
  
  #define SBC7240_OPEN_STATUS_BIT		0
  #define SBC7240_ENABLED_STATUS_BIT	1
  #define SBC7240_EXPECT_CLOSE_STATUS_BIT	2
  static unsigned long wdt_status;
  
  /*
   * Utility routines
   */
  
  static void wdt_disable(void)
  {
  	/* disable the watchdog */
  	if (test_and_clear_bit(SBC7240_ENABLED_STATUS_BIT, &wdt_status)) {
  		inb_p(SBC7240_DISABLE_PORT);
  		pr_info("Watchdog timer is now disabled
  ");
  	}
  }
  
  static void wdt_enable(void)
  {
  	/* enable the watchdog */
  	if (!test_and_set_bit(SBC7240_ENABLED_STATUS_BIT, &wdt_status)) {
  		inb_p(SBC7240_ENABLE_PORT);
  		pr_info("Watchdog timer is now enabled
  ");
  	}
  }
  
  static int wdt_set_timeout(int t)
  {
  	if (t < 1 || t > SBC7240_MAX_TIMEOUT) {
  		pr_err("timeout value must be 1<=x<=%d
  ", SBC7240_MAX_TIMEOUT);
  		return -1;
  	}
  	/* set the timeout */
  	outb_p((unsigned)t, SBC7240_SET_TIMEOUT_PORT);
  	timeout = t;
  	pr_info("timeout set to %d seconds
  ", t);
  	return 0;
  }
  
  /* Whack the dog */
  static inline void wdt_keepalive(void)
  {
  	if (test_bit(SBC7240_ENABLED_STATUS_BIT, &wdt_status))
  		inb_p(SBC7240_ENABLE_PORT);
  }
  
  /*
   * /dev/watchdog handling
   */
  static ssize_t fop_write(struct file *file, const char __user *buf,
  			 size_t count, loff_t *ppos)
  {
  	size_t i;
  	char c;
  
  	if (count) {
  		if (!nowayout) {
  			clear_bit(SBC7240_EXPECT_CLOSE_STATUS_BIT,
  				&wdt_status);
  
  			/* is there a magic char ? */
  			for (i = 0; i != count; i++) {
  				if (get_user(c, buf + i))
  					return -EFAULT;
  				if (c == SBC7240_MAGIC_CHAR) {
  					set_bit(SBC7240_EXPECT_CLOSE_STATUS_BIT,
  						&wdt_status);
  					break;
  				}
  			}
  		}
  
  		wdt_keepalive();
  	}
  
  	return count;
  }
  
  static int fop_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(SBC7240_OPEN_STATUS_BIT, &wdt_status))
  		return -EBUSY;
  
  	wdt_enable();
  
  	return nonseekable_open(inode, file);
  }
  
  static int fop_close(struct inode *inode, struct file *file)
  {
  	if (test_and_clear_bit(SBC7240_EXPECT_CLOSE_STATUS_BIT, &wdt_status)
  	    || !nowayout) {
  		wdt_disable();
  	} else {
  		pr_crit("Unexpected close, not stopping watchdog!
  ");
  		wdt_keepalive();
  	}
  
  	clear_bit(SBC7240_OPEN_STATUS_BIT, &wdt_status);
  	return 0;
  }
  
  static const struct watchdog_info ident = {
  	.options = WDIOF_KEEPALIVEPING|
  		   WDIOF_SETTIMEOUT|
  		   WDIOF_MAGICCLOSE,
  	.firmware_version = 1,
  	.identity = "SBC7240",
  };
  
  
  static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		return copy_to_user((void __user *)arg, &ident, sizeof(ident))
  						 ? -EFAULT : 0;
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, (int __user *)arg);
  	case WDIOC_SETOPTIONS:
  	{
  		int options;
  		int retval = -EINVAL;
  
  		if (get_user(options, (int __user *)arg))
  			return -EFAULT;
  
  		if (options & WDIOS_DISABLECARD) {
  			wdt_disable();
  			retval = 0;
  		}
  
  		if (options & WDIOS_ENABLECARD) {
  			wdt_enable();
  			retval = 0;
  		}
  
  		return retval;
  	}
  	case WDIOC_KEEPALIVE:
  		wdt_keepalive();
  		return 0;
  	case WDIOC_SETTIMEOUT:
  	{
  		int new_timeout;
  
  		if (get_user(new_timeout, (int __user *)arg))
  			return -EFAULT;
  
  		if (wdt_set_timeout(new_timeout))
  			return -EINVAL;
  
  		/* Fall through */
  	}
  	case WDIOC_GETTIMEOUT:
  		return put_user(timeout, (int __user *)arg);
  	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_disable();
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block wdt_notifier = {
  	.notifier_call = wdt_notify_sys,
  };
  
  static void __exit sbc7240_wdt_unload(void)
  {
  	pr_info("Removing watchdog
  ");
  	misc_deregister(&wdt_miscdev);
  
  	unregister_reboot_notifier(&wdt_notifier);
  	release_region(SBC7240_ENABLE_PORT, 1);
  }
  
  static int __init sbc7240_wdt_init(void)
  {
  	int rc = -EBUSY;
  
  	if (!request_region(SBC7240_ENABLE_PORT, 1, "SBC7240 WDT")) {
  		pr_err("I/O address 0x%04x already in use
  ",
  		       SBC7240_ENABLE_PORT);
  		rc = -EIO;
  		goto err_out;
  	}
  
  	/* The IO port 0x043 used to disable the watchdog
  	 * is already claimed by the system timer, so we
  	 * can't request_region() it ...*/
  
  	if (timeout < 1 || timeout > SBC7240_MAX_TIMEOUT) {
  		timeout = SBC7240_TIMEOUT;
  		pr_info("timeout value must be 1<=x<=%d, using %d
  ",
  			SBC7240_MAX_TIMEOUT, timeout);
  	}
  	wdt_set_timeout(timeout);
  	wdt_disable();
  
  	rc = register_reboot_notifier(&wdt_notifier);
  	if (rc) {
  		pr_err("cannot register reboot notifier (err=%d)
  ", rc);
  		goto err_out_region;
  	}
  
  	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_notifier;
  	}
  
  	pr_info("Watchdog driver for SBC7240 initialised (nowayout=%d)
  ",
  		nowayout);
  
  	return 0;
  
  err_out_reboot_notifier:
  	unregister_reboot_notifier(&wdt_notifier);
  err_out_region:
  	release_region(SBC7240_ENABLE_PORT, 1);
  err_out:
  	return rc;
  }
  
  module_init(sbc7240_wdt_init);
  module_exit(sbc7240_wdt_unload);
  
  MODULE_AUTHOR("Gilles Gigan");
  MODULE_DESCRIPTION("Watchdog device driver for single board"
  		   " computers EPIC Nano 7240 from iEi");
  MODULE_LICENSE("GPL");