/*
 *      w83697hf/hg WDT driver
 *
 *      (c) Copyright 2006 Samuel Tardieu <sam@rfc1149.net>
 *      (c) Copyright 2006 Marcus Junker <junker@anduras.de>
 *
 *      Based on w83627hf_wdt.c which is based on advantechwdt.c
 *      which is based on wdt.c.
 *      Original copyright messages:
 *
 *      (c) Copyright 2003 Pádraig Brady <P@draigBrady.com>
 *
 *      (c) Copyright 2000-2001 Marek Michalkiewicz <marekm@linux.org.pl>
 *
 *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 *
 *      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 Marcus Junker nor ANDURAS AG admit liability nor provide
 *      warranty for any of this software. This material is provided
 *      "AS-IS" and at no charge.
 */

#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 "w83697hf/hg WDT"
#define WATCHDOG_TIMEOUT 60             /* 60 sec default timeout */
#define WATCHDOG_EARLY_DISABLE 1        /* Disable until userland kicks in */

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

/* You must set this - there is no sane way to probe for this board. */
static int wdt_io = 0x2e;
module_param(wdt_io, int, 0);
MODULE_PARM_DESC(wdt_io,
                "w83697hf/hg WDT io port (default 0x2e, 0 = autodetect)");

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) ")");

static int early_disable = WATCHDOG_EARLY_DISABLE;
module_param(early_disable, int, 0);
MODULE_PARM_DESC(early_disable,
        "Watchdog gets disabled at boot time (default="
                                __MODULE_STRING(WATCHDOG_EARLY_DISABLE) ")");

/*
 *      Kernel methods.
 */

#define W83697HF_EFER (wdt_io + 0)  /* Extended Function Enable Register */
#define W83697HF_EFIR (wdt_io + 0)  /* Extended Function Index Register
                                                        (same as EFER) */
#define W83697HF_EFDR (wdt_io + 1)  /* Extended Function Data Register */

static inline void w83697hf_unlock(void)
{
        outb_p(0x87, W83697HF_EFER);    /* Enter extended function mode */
        outb_p(0x87, W83697HF_EFER);    /* Again according to manual */
}

static inline void w83697hf_lock(void)
{
        outb_p(0xAA, W83697HF_EFER);    /* Leave extended function mode */
}

/*
 *      The three functions w83697hf_get_reg(), w83697hf_set_reg() and
 *      w83697hf_write_timeout() must be called with the device unlocked.
 */

static unsigned char w83697hf_get_reg(unsigned char reg)
{
        outb_p(reg, W83697HF_EFIR);
        return inb_p(W83697HF_EFDR);
}

static void w83697hf_set_reg(unsigned char reg, unsigned char data)
{
        outb_p(reg, W83697HF_EFIR);
        outb_p(data, W83697HF_EFDR);
}

static void w83697hf_write_timeout(int timeout)
{
        /* Write Timeout counter to CRF4 */
        w83697hf_set_reg(0xF4, timeout);
}

static void w83697hf_select_wdt(void)
{
        w83697hf_unlock();
        w83697hf_set_reg(0x07, 0x08);   /* Switch to logic device 8 (GPIO2) */
}

static inline void w83697hf_deselect_wdt(void)
{
        w83697hf_lock();
}

static void w83697hf_init(void)
{
        unsigned char bbuf;

        w83697hf_select_wdt();

        bbuf = w83697hf_get_reg(0x29);
        bbuf &= ~0x60;
        bbuf |= 0x20;

        /* Set pin 119 to WDTO# mode (= CR29, WDT0) */
        w83697hf_set_reg(0x29, bbuf);

        bbuf = w83697hf_get_reg(0xF3);
        bbuf &= ~0x04;
        w83697hf_set_reg(0xF3, bbuf);   /* Count mode is seconds */

        w83697hf_deselect_wdt();
}

static void wdt_ping(void)
{
        spin_lock(&io_lock);
        w83697hf_select_wdt();

        w83697hf_write_timeout(timeout);

        w83697hf_deselect_wdt();
        spin_unlock(&io_lock);
}

static void wdt_enable(void)
{
        spin_lock(&io_lock);
        w83697hf_select_wdt();

        w83697hf_write_timeout(timeout);
        w83697hf_set_reg(0x30, 1);      /* Enable timer */

        w83697hf_deselect_wdt();
        spin_unlock(&io_lock);
}

static void wdt_disable(void)
{
        spin_lock(&io_lock);
        w83697hf_select_wdt();

        w83697hf_set_reg(0x30, 0);      /* Disable timer */
        w83697hf_write_timeout(0);

        w83697hf_deselect_wdt();
        spin_unlock(&io_lock);
}

static unsigned char wdt_running(void)
{
        unsigned char t;

        spin_lock(&io_lock);
        w83697hf_select_wdt();

        t = w83697hf_get_reg(0xF4);     /* Read timer */

        w83697hf_deselect_wdt();
        spin_unlock(&io_lock);

        return t;
}

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 = "W83697HF 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_enable();
                        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_enable();
        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 w83697hf_check_wdt(void)
{
        if (!request_region(wdt_io, 2, WATCHDOG_NAME)) {
                pr_err("I/O address 0x%x already in use\n", wdt_io);
                return -EIO;
        }

        pr_debug("Looking for watchdog at address 0x%x\n", wdt_io);
        w83697hf_unlock();
        if (w83697hf_get_reg(0x20) == 0x60) {
                pr_info("watchdog found at address 0x%x\n", wdt_io);
                w83697hf_lock();
                return 0;
        }
        /* Reprotect in case it was a compatible device */
        w83697hf_lock();

        pr_info("watchdog not found at address 0x%x\n", wdt_io);
        release_region(wdt_io, 2);
        return -EIO;
}

static int w83697hf_ioports[] = { 0x2e, 0x4e, 0x00 };

static int __init wdt_init(void)
{
        int ret, i, found = 0;

        pr_info("WDT driver for W83697HF/HG initializing\n");

        if (wdt_io == 0) {
                /* we will autodetect the W83697HF/HG watchdog */
                for (i = 0; ((!found) && (w83697hf_ioports[i] != 0)); i++) {
                        wdt_io = w83697hf_ioports[i];
                        if (!w83697hf_check_wdt())
                                found++;
                }
        } else {
                if (!w83697hf_check_wdt())
                        found++;
        }

        if (!found) {
                pr_err("No W83697HF/HG could be found\n");
                ret = -EIO;
                goto out;
        }

        w83697hf_init();
        if (early_disable) {
                if (wdt_running())
                        pr_warn("Stopping previously enabled watchdog until userland kicks in\n");
                wdt_disable();
        }

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

        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, 2);
        goto out;
}

static void __exit wdt_exit(void)
{
        misc_deregister(&wdt_miscdev);
        unregister_reboot_notifier(&wdt_notifier);
        release_region(wdt_io, 2);
}

module_init(wdt_init);
module_exit(wdt_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marcus Junker <junker@anduras.de>, "
                "Samuel Tardieu <sam@rfc1149.net>");
MODULE_DESCRIPTION("w83697hf/hg WDT driver");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);