/*
 *	IT8712F "Smart Guardian" Watchdog support
 *
 *	Copyright (c) 2006-2007 Jorge Boncompte - DTI2 <jorge@dti2.net>
 *
 *	Based on info and code taken from:
 *
 *	drivers/char/watchdog/scx200_wdt.c
 *	drivers/hwmon/it87.c
 *	IT8712F EC-LPC I/O Preliminary Specification 0.9.2.pdf
 *
 *	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 author(s) of this software shall not be held liable for damages
 *	of any nature resulting due to the use of this software. This
 *	software is provided AS-IS with no warranties.
 */

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

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

#define NAME "it8712f_wdt"

MODULE_AUTHOR("Jorge Boncompte - DTI2 <jorge@dti2.net>");
MODULE_DESCRIPTION("IT8712F Watchdog Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

static int margin = 60;		/* in seconds */
module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds");

static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");

static struct semaphore it8712f_wdt_sem;
static unsigned expect_close;
static spinlock_t io_lock;

/* Dog Food address - We use the game port address */
static unsigned short address;

#define	REG		0x2e	/* The register to read/write */
#define	VAL		0x2f	/* The value to read/write */

#define	LDN		0x07	/* Register: Logical device select */
#define	DEVID		0x20	/* Register: Device ID */
#define	DEVREV		0x22	/* Register: Device Revision */
#define ACT_REG		0x30	/* LDN Register: Activation */
#define BASE_REG	0x60	/* LDN Register: Base address */

#define IT8712F_DEVID	0x8712

#define LDN_GPIO	0x07	/* GPIO and Watch Dog Timer */
#define LDN_GAME 	0x09	/* Game Port */

#define WDT_CONTROL	0x71	/* WDT Register: Control */
#define WDT_CONFIG	0x72	/* WDT Register: Configuration */
#define WDT_TIMEOUT	0x73	/* WDT Register: Timeout Value */

#define WDT_RESET_GAME	0x10
#define WDT_RESET_KBD	0x20
#define WDT_RESET_MOUSE	0x40
#define WDT_RESET_CIR	0x80

#define WDT_UNIT_SEC	0x80	/* If 0 in MINUTES */

#define WDT_OUT_PWROK	0x10
#define WDT_OUT_KRST	0x40

static int
superio_inb(int reg)
{
	outb(reg, REG);
	return inb(VAL);
}

static void
superio_outb(int val, int reg)
{
	outb(reg, REG);
	outb(val, VAL);
}

static int
superio_inw(int reg)
{
	int val;
	outb(reg++, REG);
	val = inb(VAL) << 8;
	outb(reg, REG);
	val |= inb(VAL);
	return val;
}

static inline void
superio_select(int ldn)
{
	outb(LDN, REG);
	outb(ldn, VAL);
}

static inline void
superio_enter(void)
{
	spin_lock(&io_lock);
	outb(0x87, REG);
	outb(0x01, REG);
	outb(0x55, REG);
	outb(0x55, REG);
}

static inline void
superio_exit(void)
{
	outb(0x02, REG);
	outb(0x02, VAL);
	spin_unlock(&io_lock);
}

static inline void
it8712f_wdt_ping(void)
{
	inb(address);
}

static void
it8712f_wdt_update_margin(void)
{
	int config = WDT_OUT_KRST | WDT_OUT_PWROK;

	printk(KERN_INFO NAME ": timer margin %d seconds\n", margin);

	/* The timeout register only has 8bits wide */
	if (margin < 256)
		config |= WDT_UNIT_SEC;	/* else UNIT are MINUTES */
	superio_outb(config, WDT_CONFIG);

	superio_outb((margin > 255) ? (margin / 60) : margin, WDT_TIMEOUT);
}

static void
it8712f_wdt_enable(void)
{
	printk(KERN_DEBUG NAME ": enabling watchdog timer\n");
	superio_enter();
	superio_select(LDN_GPIO);

	superio_outb(WDT_RESET_GAME, WDT_CONTROL);

	it8712f_wdt_update_margin();

	superio_exit();

	it8712f_wdt_ping();
}

static void
it8712f_wdt_disable(void)
{
	printk(KERN_DEBUG NAME ": disabling watchdog timer\n");

	superio_enter();
	superio_select(LDN_GPIO);

	superio_outb(0, WDT_CONFIG);
	superio_outb(0, WDT_CONTROL);
	superio_outb(0, WDT_TIMEOUT);

	superio_exit();
}

static int
it8712f_wdt_notify(struct notifier_block *this,
		    unsigned long code, void *unused)
{
	if (code == SYS_HALT || code == SYS_POWER_OFF)
		if (!nowayout)
			it8712f_wdt_disable();

	return NOTIFY_DONE;
}

static struct notifier_block it8712f_wdt_notifier = {
	.notifier_call = it8712f_wdt_notify,
};

static ssize_t
it8712f_wdt_write(struct file *file, const char __user *data,
	size_t len, loff_t *ppos)
{
	/* check for a magic close character */
	if (len) {
		size_t i;

		it8712f_wdt_ping();

		expect_close = 0;
		for (i = 0; i < len; ++i) {
			char c;
			if (get_user(c, data+i))
				return -EFAULT;
			if (c == 'V')
				expect_close = 42;
		}
	}

	return len;
}

static int
it8712f_wdt_ioctl(struct inode *inode, struct file *file,
	unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	static struct watchdog_info ident = {
		.identity = "IT8712F Watchdog",
		.firmware_version = 1,
		.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
	};
	int new_margin;

	switch (cmd) {
	default:
		return -ENOTTY;
	case WDIOC_GETSUPPORT:
		if (copy_to_user(argp, &ident, sizeof(ident)))
			return -EFAULT;
		return 0;
	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(0, p);
	case WDIOC_KEEPALIVE:
		it8712f_wdt_ping();
		return 0;
	case WDIOC_SETTIMEOUT:
		if (get_user(new_margin, p))
			return -EFAULT;
		if (new_margin < 1)
			return -EINVAL;
		margin = new_margin;
		superio_enter();
		superio_select(LDN_GPIO);

		it8712f_wdt_update_margin();

		superio_exit();
		it8712f_wdt_ping();
	case WDIOC_GETTIMEOUT:
		if (put_user(margin, p))
			return -EFAULT;
		return 0;
	}
}

static int
it8712f_wdt_open(struct inode *inode, struct file *file)
{
	/* only allow one at a time */
	if (down_trylock(&it8712f_wdt_sem))
		return -EBUSY;
	it8712f_wdt_enable();

	return nonseekable_open(inode, file);
}

static int
it8712f_wdt_release(struct inode *inode, struct file *file)
{
	if (expect_close != 42) {
		printk(KERN_WARNING NAME
			": watchdog device closed unexpectedly, will not"
			" disable the watchdog timer\n");
	} else if (!nowayout) {
		it8712f_wdt_disable();
	}
	expect_close = 0;
	up(&it8712f_wdt_sem);

	return 0;
}

static const struct file_operations it8712f_wdt_fops = {
	.owner = THIS_MODULE,
	.llseek = no_llseek,
	.write = it8712f_wdt_write,
	.ioctl = it8712f_wdt_ioctl,
	.open = it8712f_wdt_open,
	.release = it8712f_wdt_release,
};

static struct miscdevice it8712f_wdt_miscdev = {
	.minor = WATCHDOG_MINOR,
	.name = "watchdog",
	.fops = &it8712f_wdt_fops,
};

static int __init
it8712f_wdt_find(unsigned short *address)
{
	int err = -ENODEV;
	int chip_type;

	superio_enter();
	chip_type = superio_inw(DEVID);
	if (chip_type != IT8712F_DEVID)
		goto exit;

	superio_select(LDN_GAME);
	superio_outb(1, ACT_REG);
	if (!(superio_inb(ACT_REG) & 0x01)) {
		printk(KERN_ERR NAME ": Device not activated, skipping\n");
		goto exit;
	}

	*address = superio_inw(BASE_REG);
	if (*address == 0) {
		printk(KERN_ERR NAME ": Base address not set, skipping\n");
		goto exit;
	}

	err = 0;
	printk(KERN_DEBUG NAME ": Found IT%04xF chip revision %d - "
		"using DogFood address 0x%x\n",
		chip_type, superio_inb(DEVREV) & 0x0f, *address);

exit:
	superio_exit();
	return err;
}

static int __init
it8712f_wdt_init(void)
{
	int err = 0;

	spin_lock_init(&io_lock);

	if (it8712f_wdt_find(&address))
		return -ENODEV;

	if (!request_region(address, 1, "IT8712F Watchdog")) {
		printk(KERN_WARNING NAME ": watchdog I/O region busy\n");
		return -EBUSY;
	}

	it8712f_wdt_disable();

	sema_init(&it8712f_wdt_sem, 1);

	err = register_reboot_notifier(&it8712f_wdt_notifier);
	if (err) {
		printk(KERN_ERR NAME ": unable to register reboot notifier\n");
		goto out;
	}

	err = misc_register(&it8712f_wdt_miscdev);
	if (err) {
		printk(KERN_ERR NAME
			": cannot register miscdev on minor=%d (err=%d)\n",
			WATCHDOG_MINOR, err);
		goto reboot_out;
	}

	return 0;


reboot_out:
	unregister_reboot_notifier(&it8712f_wdt_notifier);
out:
	release_region(address, 1);
	return err;
}

static void __exit
it8712f_wdt_exit(void)
{
	misc_deregister(&it8712f_wdt_miscdev);
	unregister_reboot_notifier(&it8712f_wdt_notifier);
	release_region(address, 1);
}

module_init(it8712f_wdt_init);
module_exit(it8712f_wdt_exit);