// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *	IndyDog	0.3	A Hardware Watchdog Device for SGI IP22
   *

   *	(c) Copyright 2002 Guido Guenther <agx@sigxcpu.org>,
   *						All Rights Reserved.

   *

   *	based on softdog.c by Alan Cox <alan@lxorguk.ukuu.org.uk>

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>
  #include <linux/moduleparam.h>

  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/notifier.h>
  #include <linux/reboot.h>
  #include <linux/init.h>

  #include <linux/uaccess.h>

  #include <asm/sgi/mc.h>

  static unsigned long indydog_alive;

  static DEFINE_SPINLOCK(indydog_lock);

  #define WATCHDOG_TIMEOUT 30		/* 30 sec default 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 indydog_start(void)
  {

  	spin_lock(&indydog_lock);

  	sgimc->cpuctrl0 |= SGIMC_CCTRL0_WDOG;

  	spin_unlock(&indydog_lock);

  }
  
  static void indydog_stop(void)
  {

  	spin_lock(&indydog_lock);

  	sgimc->cpuctrl0 &= ~SGIMC_CCTRL0_WDOG;

  	spin_unlock(&indydog_lock);

  	pr_info("Stopped watchdog timer
  ");

  }
  
  static void indydog_ping(void)
  {
  	sgimc->watchdogt = 0;
  }
  
  /*
   *	Allow only one person to hold it open
   */
  static int indydog_open(struct inode *inode, struct file *file)
  {

  	if (test_and_set_bit(0, &indydog_alive))

  		return -EBUSY;
  
  	if (nowayout)
  		__module_get(THIS_MODULE);
  
  	/* Activate timer */
  	indydog_start();
  	indydog_ping();

  	pr_info("Started watchdog timer
  ");

  	return stream_open(inode, file);

  }
  
  static int indydog_release(struct inode *inode, struct file *file)
  {
  	/* Shut off the timer.
  	 * Lock it in if it's a module and we defined ...NOWAYOUT */
  	if (!nowayout)
  		indydog_stop();		/* Turn the WDT off */

  	clear_bit(0, &indydog_alive);

  	return 0;
  }

  static ssize_t indydog_write(struct file *file, const char *data,
  						size_t len, loff_t *ppos)

  {
  	/* Refresh the timer. */

  	if (len)

  		indydog_ping();

  	return len;
  }

  static long indydog_ioctl(struct file *file, unsigned int cmd,
  							unsigned long arg)

  {
  	int options, retval = -EINVAL;

  	static const struct watchdog_info ident = {

  		.options		= WDIOF_KEEPALIVEPING,

  		.firmware_version	= 0,
  		.identity		= "Hardware Watchdog for SGI IP22",
  	};
  
  	switch (cmd) {

  	case WDIOC_GETSUPPORT:
  		if (copy_to_user((struct watchdog_info *)arg,
  				 &ident, sizeof(ident)))
  			return -EFAULT;
  		return 0;
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, (int *)arg);

  	case WDIOC_SETOPTIONS:
  	{
  		if (get_user(options, (int *)arg))
  			return -EFAULT;
  		if (options & WDIOS_DISABLECARD) {
  			indydog_stop();
  			retval = 0;
  		}
  		if (options & WDIOS_ENABLECARD) {
  			indydog_start();
  			retval = 0;

  		}

  		return retval;
  	}

  	case WDIOC_KEEPALIVE:
  		indydog_ping();
  		return 0;
  	case WDIOC_GETTIMEOUT:
  		return put_user(WATCHDOG_TIMEOUT, (int *)arg);

  	default:
  		return -ENOTTY;

  	}
  }

  static int indydog_notify_sys(struct notifier_block *this,
  					unsigned long code, void *unused)

  {
  	if (code == SYS_DOWN || code == SYS_HALT)
  		indydog_stop();		/* Turn the WDT off */
  
  	return NOTIFY_DONE;
  }

  static const struct file_operations indydog_fops = {

  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= indydog_write,

  	.unlocked_ioctl	= indydog_ioctl,

  	.compat_ioctl	= compat_ptr_ioctl,

  	.open		= indydog_open,
  	.release	= indydog_release,
  };
  
  static struct miscdevice indydog_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &indydog_fops,
  };
  
  static struct notifier_block indydog_notifier = {
  	.notifier_call = indydog_notify_sys,
  };

  static int __init watchdog_init(void)
  {
  	int ret;
  
  	ret = register_reboot_notifier(&indydog_notifier);
  	if (ret) {

  		pr_err("cannot register reboot notifier (err=%d)
  ", ret);

  		return ret;
  	}
  
  	ret = misc_register(&indydog_miscdev);
  	if (ret) {

  		pr_err("cannot register miscdev on minor=%d (err=%d)
  ",
  		       WATCHDOG_MINOR, ret);

  		unregister_reboot_notifier(&indydog_notifier);
  		return ret;
  	}

  	pr_info("Hardware Watchdog Timer for SGI IP22: 0.3
  ");

  
  	return 0;
  }
  
  static void __exit watchdog_exit(void)
  {
  	misc_deregister(&indydog_miscdev);
  	unregister_reboot_notifier(&indydog_notifier);
  }
  
  module_init(watchdog_init);
  module_exit(watchdog_exit);
  
  MODULE_AUTHOR("Guido Guenther <agx@sigxcpu.org>");
  MODULE_DESCRIPTION("Hardware Watchdog Device for SGI IP22");
  MODULE_LICENSE("GPL");