/*
   *	SMsC 37B787 Watchdog Timer driver for Linux 2.6.x.x
   *
   *	Based on acquirewdt.c by Alan Cox <alan@lxorguk.ukuu.org.uk>
   *	and some other existing drivers
   *
   *	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 authors do 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 2003-2006  Sven Anders <anders@anduras.de>
   *
   *  History:
   *	2003 - Created version 1.0 for Linux 2.4.x.
   *	2006 - Ported to Linux 2.6, added nowayout and MAGICCLOSE
   *	       features. Released version 1.1
   *
   *  Theory of operation:
   *
   *	A Watchdog Timer (WDT) is a hardware circuit that can
   *	reset the computer system in case of a software fault.
   *	You probably knew that already.
   *
   *	Usually a userspace daemon will notify the kernel WDT driver
   *	via the /dev/watchdog special device file that userspace is
   *	still alive, at regular intervals.  When such a notification
   *	occurs, the driver will usually tell the hardware watchdog
   *	that everything is in order, and that the watchdog should wait
   *	for yet another little while to reset the system.
   *	If userspace fails (RAM error, kernel bug, whatever), the
   *	notifications cease to occur, and the hardware watchdog will
   *	reset the system (causing a reboot) after the timeout occurs.
   *
   * Create device with:
   *  mknod /dev/watchdog c 10 130
   *
   * For an example userspace keep-alive daemon, see:
   *   Documentation/watchdog/wdt.txt
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/types.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/delay.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>
  
  
  /* enable support for minutes as units? */
  /* (does not always work correctly, so disabled by default!) */
  #define SMSC_SUPPORT_MINUTES
  #undef SMSC_SUPPORT_MINUTES
  
  #define MAX_TIMEOUT     255
  
  #define UNIT_SECOND     0
  #define UNIT_MINUTE     1
  
  #define VERSION		"1.1"
  
  #define IOPORT		0x3F0
  #define IOPORT_SIZE     2
  #define IODEV_NO	8
  
  static int unit = UNIT_SECOND;	/* timer's unit */
  static int timeout = 60;	/* timeout value: default is 60 "units" */
  static unsigned long timer_enabled;   /* is the timer enabled? */
  
  static char expect_close;       /* is the close expected? */
  
  static DEFINE_SPINLOCK(io_lock);/* to guard the watchdog from io races */
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  
  /* -- Low level function ----------------------------------------*/
  
  /* unlock the IO chip */
  
  static inline void open_io_config(void)
  {
  	outb(0x55, IOPORT);
  	mdelay(1);
  	outb(0x55, IOPORT);
  }
  
  /* lock the IO chip */
  static inline void close_io_config(void)
  {
  	outb(0xAA, IOPORT);
  }
  
  /* select the IO device */
  static inline void select_io_device(unsigned char devno)
  {
  	outb(0x07, IOPORT);
  	outb(devno, IOPORT+1);
  }
  
  /* write to the control register */
  static inline void write_io_cr(unsigned char reg, unsigned char data)
  {
  	outb(reg, IOPORT);
  	outb(data, IOPORT+1);
  }
  
  /* read from the control register */
  static inline char read_io_cr(unsigned char reg)
  {
  	outb(reg, IOPORT);
  	return inb(IOPORT+1);
  }
  
  /* -- Medium level functions ------------------------------------*/
  
  static inline void gpio_bit12(unsigned char reg)
  {
  	/* -- General Purpose I/O Bit 1.2 --
  	 * Bit 0,   In/Out: 0 = Output, 1 = Input
  	 * Bit 1,   Polarity: 0 = No Invert, 1 = Invert
  	 * Bit 2,   Group Enable Intr.: 0 = Disable, 1 = Enable
  	 * Bit 3/4, Function select: 00 = GPI/O, 01 = WDT, 10 = P17,
  	 *                           11 = Either Edge Triggered Intr. 2
  	 * Bit 5/6  (Reserved)
  	 * Bit 7,   Output Type: 0 = Push Pull Bit, 1 = Open Drain
  	 */
  	write_io_cr(0xE2, reg);
  }
  
  static inline void gpio_bit13(unsigned char reg)
  {
  	/* -- General Purpose I/O Bit 1.3 --
  	 * Bit 0,  In/Out: 0 = Output, 1 = Input
  	 * Bit 1,  Polarity: 0 = No Invert, 1 = Invert
  	 * Bit 2,  Group Enable Intr.: 0 = Disable, 1 = Enable
  	 * Bit 3,  Function select: 0 = GPI/O, 1 = LED
  	 * Bit 4-6 (Reserved)
  	 * Bit 7,  Output Type: 0 = Push Pull Bit, 1 = Open Drain
  	 */
  	write_io_cr(0xE3, reg);
  }
  
  static inline void wdt_timer_units(unsigned char new_units)
  {
  	/* -- Watchdog timer units --
  	 * Bit 0-6 (Reserved)
  	 * Bit 7,  WDT Time-out Value Units Select
  	 *         (0 = Minutes, 1 = Seconds)
  	 */
  	write_io_cr(0xF1, new_units);
  }
  
  static inline void wdt_timeout_value(unsigned char new_timeout)
  {
  	/* -- Watchdog Timer Time-out Value --
  	 * Bit 0-7 Binary coded units (0=Disabled, 1..255)
  	 */
  	write_io_cr(0xF2, new_timeout);
  }
  
  static inline void wdt_timer_conf(unsigned char conf)
  {
  	/* -- Watchdog timer configuration --
  	 * Bit 0   Joystick enable: 0* = No Reset, 1 = Reset WDT upon
  	 *							Gameport I/O
  	 * Bit 1   Keyboard enable: 0* = No Reset, 1 = Reset WDT upon KBD Intr.
  	 * Bit 2   Mouse enable: 0* = No Reset, 1 = Reset WDT upon Mouse Intr
  	 * Bit 3   Reset the timer
  	 *         (Wrong in SMsC documentation? Given as: PowerLED Timout
  	 *							Enabled)
  	 * Bit 4-7 WDT Interrupt Mapping: (0000* = Disabled,
  	 *            0001=IRQ1, 0010=(Invalid), 0011=IRQ3 to 1111=IRQ15)
  	 */
  	write_io_cr(0xF3, conf);
  }
  
  static inline void wdt_timer_ctrl(unsigned char reg)
  {
  	/* -- Watchdog timer control --
  	 * Bit 0   Status Bit: 0 = Timer counting, 1 = Timeout occurred
  	 * Bit 1   Power LED Toggle: 0 = Disable Toggle, 1 = Toggle at 1 Hz
  	 * Bit 2   Force Timeout: 1 = Forces WD timeout event (self-cleaning)
  	 * Bit 3   P20 Force Timeout enabled:
  	 *          0 = P20 activity does not generate the WD timeout event
  	 *          1 = P20 Allows rising edge of P20, from the keyboard
  	 *              controller, to force the WD timeout event.
  	 * Bit 4   (Reserved)
  	 * -- Soft power management --
  	 * Bit 5   Stop Counter: 1 = Stop software power down counter
  	 *            set via register 0xB8, (self-cleaning)
  	 *            (Upon read: 0 = Counter running, 1 = Counter stopped)
  	 * Bit 6   Restart Counter: 1 = Restart software power down counter
  	 *            set via register 0xB8, (self-cleaning)
  	 * Bit 7   SPOFF: 1 = Force software power down (self-cleaning)
  	 */
  	write_io_cr(0xF4, reg);
  }
  
  /* -- Higher level functions ------------------------------------*/
  
  /* initialize watchdog */
  
  static void wb_smsc_wdt_initialize(void)
  {
  	unsigned char old;
  
  	spin_lock(&io_lock);
  	open_io_config();
  	select_io_device(IODEV_NO);
  
  	/* enable the watchdog */
  	gpio_bit13(0x08);  /* Select pin 80 = LED not GPIO */
  	gpio_bit12(0x0A);  /* Set pin 79 = WDT not
  			      GPIO/Output/Polarity=Invert */
  	/* disable the timeout */
  	wdt_timeout_value(0);
  
  	/* reset control register */
  	wdt_timer_ctrl(0x00);
  
  	/* reset configuration register */
  	wdt_timer_conf(0x00);
  
  	/* read old (timer units) register */
  	old = read_io_cr(0xF1) & 0x7F;
  	if (unit == UNIT_SECOND)
  		old |= 0x80;	/* set to seconds */
  
  	/* set the watchdog timer units */
  	wdt_timer_units(old);
  
  	close_io_config();
  	spin_unlock(&io_lock);
  }
  
  /* shutdown the watchdog */
  
  static void wb_smsc_wdt_shutdown(void)
  {
  	spin_lock(&io_lock);
  	open_io_config();
  	select_io_device(IODEV_NO);
  
  	/* disable the watchdog */
  	gpio_bit13(0x09);
  	gpio_bit12(0x09);
  
  	/* reset watchdog config register */
  	wdt_timer_conf(0x00);
  
  	/* reset watchdog control register */
  	wdt_timer_ctrl(0x00);
  
  	/* disable timeout */
  	wdt_timeout_value(0x00);
  
  	close_io_config();
  	spin_unlock(&io_lock);
  }
  
  /* set timeout => enable watchdog */
  
  static void wb_smsc_wdt_set_timeout(unsigned char new_timeout)
  {
  	spin_lock(&io_lock);
  	open_io_config();
  	select_io_device(IODEV_NO);
  
  	/* set Power LED to blink, if we enable the timeout */
  	wdt_timer_ctrl((new_timeout == 0) ? 0x00 : 0x02);
  
  	/* set timeout value */
  	wdt_timeout_value(new_timeout);
  
  	close_io_config();
  	spin_unlock(&io_lock);
  }
  
  /* get timeout */
  
  static unsigned char wb_smsc_wdt_get_timeout(void)
  {
  	unsigned char set_timeout;
  
  	spin_lock(&io_lock);
  	open_io_config();
  	select_io_device(IODEV_NO);
  	set_timeout = read_io_cr(0xF2);
  	close_io_config();
  	spin_unlock(&io_lock);
  
  	return set_timeout;
  }
  
  /* disable watchdog */
  
  static void wb_smsc_wdt_disable(void)
  {
  	/* set the timeout to 0 to disable the watchdog */
  	wb_smsc_wdt_set_timeout(0);
  }
  
  /* enable watchdog by setting the current timeout */
  
  static void wb_smsc_wdt_enable(void)
  {
  	/* set the current timeout... */
  	wb_smsc_wdt_set_timeout(timeout);
  }
  
  /* reset the timer */
  
  static void wb_smsc_wdt_reset_timer(void)
  {
  	spin_lock(&io_lock);
  	open_io_config();
  	select_io_device(IODEV_NO);
  
  	/* reset the timer */
  	wdt_timeout_value(timeout);
  	wdt_timer_conf(0x08);
  
  	close_io_config();
  	spin_unlock(&io_lock);
  }
  
  /* return, if the watchdog is enabled (timeout is set...) */
  
  static int wb_smsc_wdt_status(void)
  {
  	return (wb_smsc_wdt_get_timeout() == 0) ? 0 : WDIOF_KEEPALIVEPING;
  }
  
  
  /* -- File operations -------------------------------------------*/
  
  /* open => enable watchdog and set initial timeout */
  
  static int wb_smsc_wdt_open(struct inode *inode, struct file *file)
  {
  	/* /dev/watchdog can only be opened once */
  
  	if (test_and_set_bit(0, &timer_enabled))
  		return -EBUSY;
  
  	if (nowayout)
  		__module_get(THIS_MODULE);
  
  	/* Reload and activate timer */
  	wb_smsc_wdt_enable();
  
  	pr_info("Watchdog enabled. Timeout set to %d %s
  ",
  		timeout, (unit == UNIT_SECOND) ? "second(s)" : "minute(s)");
  
  	return nonseekable_open(inode, file);
  }
  
  /* close => shut off the timer */
  
  static int wb_smsc_wdt_release(struct inode *inode, struct file *file)
  {
  	/* Shut off the timer. */
  
  	if (expect_close == 42) {
  		wb_smsc_wdt_disable();
  		pr_info("Watchdog disabled, sleeping again...
  ");
  	} else {
  		pr_crit("Unexpected close, not stopping watchdog!
  ");
  		wb_smsc_wdt_reset_timer();
  	}
  
  	clear_bit(0, &timer_enabled);
  	expect_close = 0;
  	return 0;
  }
  
  /* write => update the timer to keep the machine alive */
  
  static ssize_t wb_smsc_wdt_write(struct file *file, const char __user *data,
  				 size_t len, loff_t *ppos)
  {
  	/* See if we got the magic character 'V' and reload the timer */
  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			/* reset expect flag */
  			expect_close = 0;
  
  			/* scan to see whether or not we got the
  			   magic character */
  			for (i = 0; i != len; i++) {
  				char c;
  				if (get_user(c, data + i))
  					return -EFAULT;
  				if (c == 'V')
  					expect_close = 42;
  			}
  		}
  
  		/* someone wrote to us, we should reload the timer */
  		wb_smsc_wdt_reset_timer();
  	}
  	return len;
  }
  
  /* ioctl => control interface */
  
  static long wb_smsc_wdt_ioctl(struct file *file,
  					unsigned int cmd, unsigned long arg)
  {
  	int new_timeout;
  
  	union {
  		struct watchdog_info __user *ident;
  		int __user *i;
  	} uarg;
  
  	static const struct watchdog_info ident = {
  		.options =		WDIOF_KEEPALIVEPING |
  					WDIOF_SETTIMEOUT |
  					WDIOF_MAGICCLOSE,
  		.firmware_version =	0,
  		.identity =		"SMsC 37B787 Watchdog",
  	};
  
  	uarg.i = (int __user *)arg;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		return copy_to_user(uarg.ident, &ident, sizeof(ident))
  								? -EFAULT : 0;
  	case WDIOC_GETSTATUS:
  		return put_user(wb_smsc_wdt_status(), uarg.i);
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, uarg.i);
  	case WDIOC_SETOPTIONS:
  	{
  		int options, retval = -EINVAL;
  
  		if (get_user(options, uarg.i))
  			return -EFAULT;
  
  		if (options & WDIOS_DISABLECARD) {
  			wb_smsc_wdt_disable();
  			retval = 0;
  		}
  		if (options & WDIOS_ENABLECARD) {
  			wb_smsc_wdt_enable();
  			retval = 0;
  		}
  		return retval;
  	}
  	case WDIOC_KEEPALIVE:
  		wb_smsc_wdt_reset_timer();
  		return 0;
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_timeout, uarg.i))
  			return -EFAULT;
  		/* the API states this is given in secs */
  		if (unit == UNIT_MINUTE)
  			new_timeout /= 60;
  		if (new_timeout < 0 || new_timeout > MAX_TIMEOUT)
  			return -EINVAL;
  		timeout = new_timeout;
  		wb_smsc_wdt_set_timeout(timeout);
  		/* fall through and return the new timeout... */
  	case WDIOC_GETTIMEOUT:
  		new_timeout = timeout;
  		if (unit == UNIT_MINUTE)
  			new_timeout *= 60;
  		return put_user(new_timeout, uarg.i);
  	default:
  		return -ENOTTY;
  	}
  }
  
  /* -- Notifier funtions -----------------------------------------*/
  
  static int wb_smsc_wdt_notify_sys(struct notifier_block *this,
  					unsigned long code, void *unused)
  {
  	if (code == SYS_DOWN || code == SYS_HALT) {
  		/* set timeout to 0, to avoid possible race-condition */
  		timeout = 0;
  		wb_smsc_wdt_disable();
  	}
  	return NOTIFY_DONE;
  }
  
  /* -- Module's structures ---------------------------------------*/
  
  static const struct file_operations wb_smsc_wdt_fops = {
  	.owner	  = THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= wb_smsc_wdt_write,
  	.unlocked_ioctl	= wb_smsc_wdt_ioctl,
  	.open		= wb_smsc_wdt_open,
  	.release	= wb_smsc_wdt_release,
  };
  
  static struct notifier_block wb_smsc_wdt_notifier = {
  	.notifier_call  = wb_smsc_wdt_notify_sys,
  };
  
  static struct miscdevice wb_smsc_wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &wb_smsc_wdt_fops,
  };
  
  /* -- Module init functions -------------------------------------*/
  
  /* module's "constructor" */
  
  static int __init wb_smsc_wdt_init(void)
  {
  	int ret;
  
  	pr_info("SMsC 37B787 watchdog component driver "
  		VERSION " initialising...
  ");
  
  	if (!request_region(IOPORT, IOPORT_SIZE, "SMsC 37B787 watchdog")) {
  		pr_err("Unable to register IO port %#x
  ", IOPORT);
  		ret = -EBUSY;
  		goto out_pnp;
  	}
  
  	/* set new maximum, if it's too big */
  	if (timeout > MAX_TIMEOUT)
  		timeout = MAX_TIMEOUT;
  
  	/* init the watchdog timer */
  	wb_smsc_wdt_initialize();
  
  	ret = register_reboot_notifier(&wb_smsc_wdt_notifier);
  	if (ret) {
  		pr_err("Unable to register reboot notifier err = %d
  ", ret);
  		goto out_io;
  	}
  
  	ret = misc_register(&wb_smsc_wdt_miscdev);
  	if (ret) {
  		pr_err("Unable to register miscdev on minor %d
  ",
  		       WATCHDOG_MINOR);
  		goto out_rbt;
  	}
  
  	/* output info */
  	pr_info("Timeout set to %d %s
  ",
  		timeout, (unit == UNIT_SECOND) ? "second(s)" : "minute(s)");
  	pr_info("Watchdog initialized and sleeping (nowayout=%d)...
  ",
  		nowayout);
  out_clean:
  	return ret;
  
  out_rbt:
  	unregister_reboot_notifier(&wb_smsc_wdt_notifier);
  
  out_io:
  	release_region(IOPORT, IOPORT_SIZE);
  
  out_pnp:
  	goto out_clean;
  }
  
  /* module's "destructor" */
  
  static void __exit wb_smsc_wdt_exit(void)
  {
  	/* Stop the timer before we leave */
  	if (!nowayout) {
  		wb_smsc_wdt_shutdown();
  		pr_info("Watchdog disabled
  ");
  	}
  
  	misc_deregister(&wb_smsc_wdt_miscdev);
  	unregister_reboot_notifier(&wb_smsc_wdt_notifier);
  	release_region(IOPORT, IOPORT_SIZE);
  
  	pr_info("SMsC 37B787 watchdog component driver removed
  ");
  }
  
  module_init(wb_smsc_wdt_init);
  module_exit(wb_smsc_wdt_exit);
  
  MODULE_AUTHOR("Sven Anders <anders@anduras.de>");
  MODULE_DESCRIPTION("Driver for SMsC 37B787 watchdog component (Version "
  								VERSION ")");
  MODULE_LICENSE("GPL");
  
  #ifdef SMSC_SUPPORT_MINUTES
  module_param(unit, int, 0);
  MODULE_PARM_DESC(unit,
  		"set unit to use, 0=seconds or 1=minutes, default is 0");
  #endif
  
  module_param(timeout, int, 0);
  MODULE_PARM_DESC(timeout, "range is 1-255 units, default is 60");
  
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout,
  		"Watchdog cannot be stopped once started (default="
  				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");