// SPDX-License-Identifier: GPL-2.0+

  /*
   *	SBC8360 Watchdog driver
   *
   *	(c) Copyright 2005 Webcon, Inc.
   *
   *	Based on ib700wdt.c, which is based on advantechwdt.c which is based

   *	on acquirewdt.c which is based on wdt.c.

   *
   *	(c) Copyright 2001 Charles Howes <chowes@vsol.net>
   *

   *	Based on advantechwdt.c which is based on acquirewdt.c which
   *	is based on wdt.c.

   *
   *	(c) Copyright 2000-2001 Marek Michalkiewicz <marekm@linux.org.pl>
   *
   *	Based on acquirewdt.c which is based on wdt.c.
   *	Original copyright messages:
   *

   *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   *						All Rights Reserved.

   *

   *	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>

   *

   *	14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
   *	     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
   *	     Added timeout module option to override default

   *
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/ioport.h>
  #include <linux/delay.h>
  #include <linux/notifier.h>
  #include <linux/fs.h>
  #include <linux/reboot.h>
  #include <linux/init.h>
  #include <linux/spinlock.h>
  #include <linux/moduleparam.h>

  #include <linux/io.h>
  #include <linux/uaccess.h>

  
  static unsigned long sbc8360_is_open;

  static char expect_close;

  /*
   *
   * Watchdog Timer Configuration
   *
   * The function of the watchdog timer is to reset the system automatically
   * and is defined at I/O port 0120H and 0121H.  To enable the watchdog timer
   * and allow the system to reset, write appropriate values from the table
   * below to I/O port 0120H and 0121H.  To disable the timer, write a zero
   * value to I/O port 0121H for the system to stop the watchdog function.
   *
   * The following describes how the timer should be programmed (according to
   * the vendor documentation)
   *
   * Enabling Watchdog:
   * MOV AX,000AH (enable, phase I)
   * MOV DX,0120H
   * OUT DX,AX
   * MOV AX,000BH (enable, phase II)
   * MOV DX,0120H
   * OUT DX,AX
   * MOV AX,000nH (set multiplier n, from 1-4)
   * MOV DX,0120H
   * OUT DX,AX
   * MOV AX,000mH (set base timer m, from 0-F)
   * MOV DX,0121H
   * OUT DX,AX
   *
   * Reset timer:
   * MOV AX,000mH (same as set base timer, above)
   * MOV DX,0121H
   * OUT DX,AX
   *
   * Disabling Watchdog:
   * MOV AX,0000H (a zero value)
   * MOV DX,0120H
   * OUT DX,AX
   *
   * Watchdog timeout configuration values:
   *		N
   *	M |	1	2	3	4
   *	--|----------------------------------
   *	0 |	0.5s	5s	50s	100s
   *	1 |	1s	10s	100s	200s
   *	2 |	1.5s	15s	150s	300s
   *	3 |	2s	20s	200s	400s
   *	4 |	2.5s	25s	250s	500s
   *	5 |	3s	30s	300s	600s
   *	6 |	3.5s	35s	350s	700s
   *	7 |	4s	40s	400s	800s
   *	8 |	4.5s	45s	450s	900s
   *	9 |	5s	50s	500s	1000s
   *	A |	5.5s	55s	550s	1100s
   *	B |	6s	60s	600s	1200s
   *	C |	6.5s	65s	650s	1300s
   *	D |	7s	70s	700s	1400s
   *	E |	7.5s	75s	750s	1500s

   *	F |	8s	80s	800s	1600s

   *
   * Another way to say the same things is:
   *  For N=1, Timeout = (M+1) * 0.5s
   *  For N=2, Timeout = (M+1) * 5s
   *  For N=3, Timeout = (M+1) * 50s
   *  For N=4, Timeout = (M+1) * 100s
   *
   */
  
  static int wd_times[64][2] = {
  	{0, 1},			/* 0  = 0.5s */
  	{1, 1},			/* 1  = 1s   */
  	{2, 1},			/* 2  = 1.5s */
  	{3, 1},			/* 3  = 2s   */
  	{4, 1},			/* 4  = 2.5s */
  	{5, 1},			/* 5  = 3s   */
  	{6, 1},			/* 6  = 3.5s */
  	{7, 1},			/* 7  = 4s   */
  	{8, 1},			/* 8  = 4.5s */
  	{9, 1},			/* 9  = 5s   */
  	{0xA, 1},		/* 10 = 5.5s */
  	{0xB, 1},		/* 11 = 6s   */
  	{0xC, 1},		/* 12 = 6.5s */
  	{0xD, 1},		/* 13 = 7s   */
  	{0xE, 1},		/* 14 = 7.5s */
  	{0xF, 1},		/* 15 = 8s   */
  	{0, 2},			/* 16 = 5s  */
  	{1, 2},			/* 17 = 10s */
  	{2, 2},			/* 18 = 15s */
  	{3, 2},			/* 19 = 20s */
  	{4, 2},			/* 20 = 25s */
  	{5, 2},			/* 21 = 30s */
  	{6, 2},			/* 22 = 35s */
  	{7, 2},			/* 23 = 40s */
  	{8, 2},			/* 24 = 45s */
  	{9, 2},			/* 25 = 50s */
  	{0xA, 2},		/* 26 = 55s */
  	{0xB, 2},		/* 27 = 60s */
  	{0xC, 2},		/* 28 = 65s */
  	{0xD, 2},		/* 29 = 70s */
  	{0xE, 2},		/* 30 = 75s */
  	{0xF, 2},		/* 31 = 80s */
  	{0, 3},			/* 32 = 50s  */
  	{1, 3},			/* 33 = 100s */
  	{2, 3},			/* 34 = 150s */
  	{3, 3},			/* 35 = 200s */
  	{4, 3},			/* 36 = 250s */
  	{5, 3},			/* 37 = 300s */
  	{6, 3},			/* 38 = 350s */
  	{7, 3},			/* 39 = 400s */
  	{8, 3},			/* 40 = 450s */
  	{9, 3},			/* 41 = 500s */
  	{0xA, 3},		/* 42 = 550s */
  	{0xB, 3},		/* 43 = 600s */
  	{0xC, 3},		/* 44 = 650s */
  	{0xD, 3},		/* 45 = 700s */
  	{0xE, 3},		/* 46 = 750s */
  	{0xF, 3},		/* 47 = 800s */
  	{0, 4},			/* 48 = 100s */
  	{1, 4},			/* 49 = 200s */
  	{2, 4},			/* 50 = 300s */
  	{3, 4},			/* 51 = 400s */
  	{4, 4},			/* 52 = 500s */
  	{5, 4},			/* 53 = 600s */
  	{6, 4},			/* 54 = 700s */
  	{7, 4},			/* 55 = 800s */
  	{8, 4},			/* 56 = 900s */
  	{9, 4},			/* 57 = 1000s */
  	{0xA, 4},		/* 58 = 1100s */
  	{0xB, 4},		/* 59 = 1200s */
  	{0xC, 4},		/* 60 = 1300s */
  	{0xD, 4},		/* 61 = 1400s */
  	{0xE, 4},		/* 62 = 1500s */
  	{0xF, 4}		/* 63 = 1600s */
  };
  
  #define SBC8360_ENABLE 0x120
  #define SBC8360_BASETIME 0x121
  
  static int timeout = 27;
  static int wd_margin = 0xB;
  static int wd_multiplier = 2;

  static bool nowayout = WATCHDOG_NOWAYOUT;

  module_param(timeout, int, 0);

  MODULE_PARM_DESC(timeout, "Index into timeout table (0-63) (default=27 (60s))");

  module_param(nowayout, bool, 0);

  MODULE_PARM_DESC(nowayout,

  		 "Watchdog cannot be stopped once started (default="
  				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

  
  /*
   *	Kernel methods.
   */
  
  /* Activate and pre-configure watchdog */
  static void sbc8360_activate(void)
  {
  	/* Enable the watchdog */
  	outb(0x0A, SBC8360_ENABLE);
  	msleep_interruptible(100);
  	outb(0x0B, SBC8360_ENABLE);
  	msleep_interruptible(100);
  	/* Set timeout multiplier */
  	outb(wd_multiplier, SBC8360_ENABLE);
  	msleep_interruptible(100);
  	/* Nothing happens until first sbc8360_ping() */
  }
  
  /* Kernel pings watchdog */
  static void sbc8360_ping(void)
  {
  	/* Write the base timer register */
  	outb(wd_margin, SBC8360_BASETIME);
  }

  /* stop watchdog */
  static void sbc8360_stop(void)
  {
  	/* De-activate the watchdog */
  	outb(0, SBC8360_ENABLE);
  }

  /* Userspace pings kernel driver, or requests clean close */

  static ssize_t sbc8360_write(struct file *file, const char __user *buf,
  			     size_t count, loff_t *ppos)

  {
  	if (count) {
  		if (!nowayout) {
  			size_t i;
  
  			/* In case it was set long ago */
  			expect_close = 0;
  
  			for (i = 0; i != count; i++) {
  				char c;
  				if (get_user(c, buf + i))
  					return -EFAULT;
  				if (c == 'V')
  					expect_close = 42;
  			}
  		}
  		sbc8360_ping();
  	}
  	return count;
  }
  
  static int sbc8360_open(struct inode *inode, struct file *file)
  {

  	if (test_and_set_bit(0, &sbc8360_is_open))

  		return -EBUSY;

  	if (nowayout)
  		__module_get(THIS_MODULE);
  
  	/* Activate and ping once to start the countdown */

  	sbc8360_activate();
  	sbc8360_ping();

  	return stream_open(inode, file);

  }
  
  static int sbc8360_close(struct inode *inode, struct file *file)
  {

  	if (expect_close == 42)

  		sbc8360_stop();

  	else

  		pr_crit("SBC8360 device closed unexpectedly.  SBC8360 will not stop!
  ");

  
  	clear_bit(0, &sbc8360_is_open);
  	expect_close = 0;

  	return 0;
  }
  
  /*
   *	Notifier for system down
   */
  
  static int sbc8360_notify_sys(struct notifier_block *this, unsigned long code,
  			      void *unused)
  {

  	if (code == SYS_DOWN || code == SYS_HALT)
  		sbc8360_stop();	/* Disable the SBC8360 Watchdog */

  	return NOTIFY_DONE;
  }
  
  /*
   *	Kernel Interfaces
   */

  static const struct file_operations sbc8360_fops = {

  	.owner = THIS_MODULE,
  	.llseek = no_llseek,
  	.write = sbc8360_write,
  	.open = sbc8360_open,
  	.release = sbc8360_close,
  };
  
  static struct miscdevice sbc8360_miscdev = {
  	.minor = WATCHDOG_MINOR,
  	.name = "watchdog",
  	.fops = &sbc8360_fops,
  };
  
  /*
   *	The SBC8360 needs to learn about soft shutdowns in order to
   *	turn the timebomb registers off.
   */
  
  static struct notifier_block sbc8360_notifier = {
  	.notifier_call = sbc8360_notify_sys,
  };
  
  static int __init sbc8360_init(void)
  {
  	int res;
  	unsigned long int mseconds = 60000;

  	if (timeout < 0 || timeout > 63) {

  		pr_err("Invalid timeout index (must be 0-63)
  ");

  		res = -EINVAL;
  		goto out;

  	}
  
  	if (!request_region(SBC8360_ENABLE, 1, "SBC8360")) {

  		pr_err("ENABLE method I/O %X is not available
  ",

  		       SBC8360_ENABLE);
  		res = -EIO;

  		goto out;

  	}
  	if (!request_region(SBC8360_BASETIME, 1, "SBC8360")) {

  		pr_err("BASETIME method I/O %X is not available
  ",

  		       SBC8360_BASETIME);
  		res = -EIO;
  		goto out_nobasetimereg;
  	}
  
  	res = register_reboot_notifier(&sbc8360_notifier);
  	if (res) {

  		pr_err("Failed to register reboot notifier
  ");

  		goto out_noreboot;
  	}

  	res = misc_register(&sbc8360_miscdev);
  	if (res) {

  		pr_err("failed to register misc device
  ");

  		goto out_nomisc;

  	}
  
  	wd_margin = wd_times[timeout][0];
  	wd_multiplier = wd_times[timeout][1];
  
  	if (wd_multiplier == 1)
  		mseconds = (wd_margin + 1) * 500;
  	else if (wd_multiplier == 2)
  		mseconds = (wd_margin + 1) * 5000;
  	else if (wd_multiplier == 3)
  		mseconds = (wd_margin + 1) * 50000;
  	else if (wd_multiplier == 4)
  		mseconds = (wd_margin + 1) * 100000;
  
  	/* My kingdom for the ability to print "0.5 seconds" in the kernel! */

  	pr_info("Timeout set at %ld ms
  ", mseconds);

  
  	return 0;

  out_nomisc:

  	unregister_reboot_notifier(&sbc8360_notifier);

  out_noreboot:

  	release_region(SBC8360_BASETIME, 1);

  out_nobasetimereg:

  	release_region(SBC8360_ENABLE, 1);

  out:

  	return res;
  }
  
  static void __exit sbc8360_exit(void)
  {
  	misc_deregister(&sbc8360_miscdev);
  	unregister_reboot_notifier(&sbc8360_notifier);
  	release_region(SBC8360_ENABLE, 1);
  	release_region(SBC8360_BASETIME, 1);
  }
  
  module_init(sbc8360_init);
  module_exit(sbc8360_exit);
  
  MODULE_AUTHOR("Ian E. Morgan <imorgan@webcon.ca>");
  MODULE_DESCRIPTION("SBC8360 watchdog driver");
  MODULE_LICENSE("GPL");

  MODULE_VERSION("1.01");

  
  /* end of sbc8360.c */