/*
 *	w83697ug/uf WDT driver
 *
 *	(c) Copyright 2008 Flemming Fransen <ff@nrvissing.net>
 *		reused original code to support w83697ug/uf.
 *
 *	Based on w83627hf_wdt.c which is based on advantechwdt.c
 *	which is based on wdt.c.
 *	Original copyright messages:
 *
 *	(c) Copyright 2007 Vlad Drukker <vlad@storewiz.com>
 *		added support for W83627THF.
 *
 *	(c) Copyright 2003 Pádraig Brady <P@draigBrady.com>
 *
 *	(c) Copyright 2000-2001 Marek Michalkiewicz <marekm@linux.org.pl>
 *
 *	(c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
 *				http://www.redhat.com
 *
 *	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.
 *
 *	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@redhat.com>
 */

#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/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>


#define WATCHDOG_NAME "w83697ug/uf WDT"
#define WATCHDOG_TIMEOUT 60		/* 60 sec default timeout */

static unsigned long wdt_is_open;
static char expect_close;
static DEFINE_SPINLOCK(io_lock);

static int wdt_io = 0x2e;
module_param(wdt_io, int, 0);
MODULE_PARM_DESC(wdt_io, "w83697ug/uf WDT io port (default 0x2e)");

static int timeout = WATCHDOG_TIMEOUT;	/* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
	"Watchdog timeout in seconds. 1<= timeout <=255 (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) ")");

/*
 *	Kernel methods.
 */

#define WDT_EFER (wdt_io+0)   /* Extended Function Enable Registers */
#define WDT_EFIR (wdt_io+0)   /* Extended Function Index Register
							(same as EFER) */
#define WDT_EFDR (WDT_EFIR+1) /* Extended Function Data Register */

static int w83697ug_select_wd_register(void)
{
	unsigned char c;
	unsigned char version;

	outb_p(0x87, WDT_EFER); /* Enter extended function mode */
	outb_p(0x87, WDT_EFER); /* Again according to manual */

	outb(0x20, WDT_EFER);	/* check chip version	*/
	version = inb(WDT_EFDR);

	if (version == 0x68) {	/* W83697UG		*/
		pr_info("Watchdog chip version 0x%02x = W83697UG/UF found at 0x%04x\n",
			version, wdt_io);

		outb_p(0x2b, WDT_EFER);
		c = inb_p(WDT_EFDR);    /* select WDT0 */
		c &= ~0x04;
		outb_p(0x2b, WDT_EFER);
		outb_p(c, WDT_EFDR);	/* set pin118 to WDT0 */

	} else {
		pr_err("No W83697UG/UF could be found\n");
		return -ENODEV;
	}

	outb_p(0x07, WDT_EFER); /* point to logical device number reg */
	outb_p(0x08, WDT_EFDR); /* select logical device 8 (GPIO2) */
	outb_p(0x30, WDT_EFER); /* select CR30 */
	c = inb_p(WDT_EFDR);
	outb_p(c | 0x01, WDT_EFDR); /* set bit 0 to activate GPIO2 */

	return 0;
}

static void w83697ug_unselect_wd_register(void)
{
	outb_p(0xAA, WDT_EFER); /* Leave extended function mode */
}

static int w83697ug_init(void)
{
	int ret;
	unsigned char t;

	ret = w83697ug_select_wd_register();
	if (ret != 0)
		return ret;

	outb_p(0xF6, WDT_EFER); /* Select CRF6 */
	t = inb_p(WDT_EFDR);    /* read CRF6 */
	if (t != 0) {
		pr_info("Watchdog already running. Resetting timeout to %d sec\n",
			timeout);
		outb_p(timeout, WDT_EFDR);    /* Write back to CRF6 */
	}
	outb_p(0xF5, WDT_EFER); /* Select CRF5 */
	t = inb_p(WDT_EFDR);    /* read CRF5 */
	t &= ~0x0C;             /* set second mode &
					disable keyboard turning off watchdog */
	outb_p(t, WDT_EFDR);    /* Write back to CRF5 */

	w83697ug_unselect_wd_register();
	return 0;
}

static void wdt_ctrl(int timeout)
{
	spin_lock(&io_lock);

	if (w83697ug_select_wd_register() < 0) {
		spin_unlock(&io_lock);
		return;
	}

	outb_p(0xF4, WDT_EFER);    /* Select CRF4 */
	outb_p(timeout, WDT_EFDR); /* Write Timeout counter to CRF4 */

	w83697ug_unselect_wd_register();

	spin_unlock(&io_lock);
}

static int wdt_ping(void)
{
	wdt_ctrl(timeout);
	return 0;
}

static int wdt_disable(void)
{
	wdt_ctrl(0);
	return 0;
}

static int wdt_set_heartbeat(int t)
{
	if (t < 1 || t > 255)
		return -EINVAL;

	timeout = t;
	return 0;
}

static ssize_t wdt_write(struct file *file, const char __user *buf,
						size_t count, loff_t *ppos)
{
	if (count) {
		if (!nowayout) {
			size_t i;

			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;
			}
		}
		wdt_ping();
	}
	return count;
}

static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int new_timeout;
	static const struct watchdog_info ident = {
		.options =		WDIOF_KEEPALIVEPING |
					WDIOF_SETTIMEOUT |
					WDIOF_MAGICCLOSE,
		.firmware_version =	1,
		.identity =		"W83697UG WDT",
	};

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		if (copy_to_user(argp, &ident, sizeof(ident)))
			return -EFAULT;
		break;

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(0, p);

	case WDIOC_SETOPTIONS:
	{
		int options, retval = -EINVAL;

		if (get_user(options, p))
			return -EFAULT;

		if (options & WDIOS_DISABLECARD) {
			wdt_disable();
			retval = 0;
		}

		if (options & WDIOS_ENABLECARD) {
			wdt_ping();
			retval = 0;
		}

		return retval;
	}

	case WDIOC_KEEPALIVE:
		wdt_ping();
		break;

	case WDIOC_SETTIMEOUT:
		if (get_user(new_timeout, p))
			return -EFAULT;
		if (wdt_set_heartbeat(new_timeout))
			return -EINVAL;
		wdt_ping();
		/* Fall */

	case WDIOC_GETTIMEOUT:
		return put_user(timeout, p);

	default:
		return -ENOTTY;
	}
	return 0;
}

static int wdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(0, &wdt_is_open))
		return -EBUSY;
	/*
	 *	Activate
	 */

	wdt_ping();
	return nonseekable_open(inode, file);
}

static int wdt_close(struct inode *inode, struct file *file)
{
	if (expect_close == 42)
		wdt_disable();
	else {
		pr_crit("Unexpected close, not stopping watchdog!\n");
		wdt_ping();
	}
	expect_close = 0;
	clear_bit(0, &wdt_is_open);
	return 0;
}

/*
 *	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();	/* Turn the WDT off */

	return NOTIFY_DONE;
}

/*
 *	Kernel Interfaces
 */

static const struct file_operations wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.write		= wdt_write,
	.unlocked_ioctl	= wdt_ioctl,
	.open		= wdt_open,
	.release	= wdt_close,
};

static struct miscdevice wdt_miscdev = {
	.minor = WATCHDOG_MINOR,
	.name = "watchdog",
	.fops = &wdt_fops,
};

/*
 *	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 int __init wdt_init(void)
{
	int ret;

	pr_info("WDT driver for the Winbond(TM) W83697UG/UF Super I/O chip initialising\n");

	if (wdt_set_heartbeat(timeout)) {
		wdt_set_heartbeat(WATCHDOG_TIMEOUT);
		pr_info("timeout value must be 1<=timeout<=255, using %d\n",
			WATCHDOG_TIMEOUT);
	}

	if (!request_region(wdt_io, 1, WATCHDOG_NAME)) {
		pr_err("I/O address 0x%04x already in use\n", wdt_io);
		ret = -EIO;
		goto out;
	}

	ret = w83697ug_init();
	if (ret != 0)
		goto unreg_regions;

	ret = register_reboot_notifier(&wdt_notifier);
	if (ret != 0) {
		pr_err("cannot register reboot notifier (err=%d)\n", ret);
		goto unreg_regions;
	}

	ret = misc_register(&wdt_miscdev);
	if (ret != 0) {
		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
		       WATCHDOG_MINOR, ret);
		goto unreg_reboot;
	}

	pr_info("initialized. timeout=%d sec (nowayout=%d)\n",
		timeout, nowayout);

out:
	return ret;
unreg_reboot:
	unregister_reboot_notifier(&wdt_notifier);
unreg_regions:
	release_region(wdt_io, 1);
	goto out;
}

static void __exit wdt_exit(void)
{
	misc_deregister(&wdt_miscdev);
	unregister_reboot_notifier(&wdt_notifier);
	release_region(wdt_io, 1);
}

module_init(wdt_init);
module_exit(wdt_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Flemming Frandsen <ff@nrvissing.net>");
MODULE_DESCRIPTION("w83697ug/uf WDT driver");