ib700wdt.c

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/*
 *  IB700 Single Board Computer WDT driver
 *
 *  (c) Copyright 2001 Charles Howes <[email protected]>
 *
 *  Based on advantechwdt.c which is based on acquirewdt.c which
 *  is based on wdt.c.
 *
 *  (c) Copyright 2000-2001 Marek Michalkiewicz <[email protected]>
 *
 *  Based on acquirewdt.c which is based on wdt.c.
 *  Original copyright messages:
 *
 *  (c) Copyright 1996 Alan Cox <[email protected]>,
 *                      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 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 <[email protected]>
 *
 *  14-Dec-2001 Matt Domsch <[email protected]>
 *       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/fs.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/uaccess.h>


static struct platform_device *ibwdt_platform_device;
static unsigned long ibwdt_is_open;
static DEFINE_SPINLOCK(ibwdt_lock);
static char expect_close;

/* Module information */
#define DRV_NAME "ib700wdt"

/*
 *
 * Watchdog Timer Configuration
 *
 * The function of the watchdog timer is to reset the system
 * automatically and is defined at I/O port 0443H.  To enable the
 * watchdog timer and allow the system to reset, write I/O port 0443H.
 * To disable the timer, write I/O port 0441H for the system to stop the
 * watchdog function.  The timer has a tolerance of 20% for its
 * intervals.
 *
 * The following describes how the timer should be programmed.
 *
 * Enabling Watchdog:
 * MOV AX,000FH (Choose the values from 0 to F)
 * MOV DX,0443H
 * OUT DX,AX
 *
 * Disabling Watchdog:
 * MOV AX,000FH (Any value is fine.)
 * MOV DX,0441H
 * OUT DX,AX
 *
 * Watchdog timer control table:
 * Level   Value  Time/sec | Level Value Time/sec
 *   1       F       0     |   9     7      16
 *   2       E       2     |   10    6      18
 *   3       D       4     |   11    5      20
 *   4       C       6     |   12    4      22
 *   5       B       8     |   13    3      24
 *   6       A       10    |   14    2      26
 *   7       9       12    |   15    1      28
 *   8       8       14    |   16    0      30
 *
 */

#define WDT_STOP 0x441
#define WDT_START 0x443

/* Default timeout */
#define WATCHDOG_TIMEOUT 30     /* 30 seconds +/- 20% */
static int timeout = WATCHDOG_TIMEOUT;  /* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
    "Watchdog timeout in seconds. 0<= timeout <=30, 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) ")");


/*
 *  Watchdog Operations
 */

static void ibwdt_ping(void)
{
    int wd_margin = 15 - ((timeout + 1) / 2);

    spin_lock(&ibwdt_lock);

    /* Write a watchdog value */
    outb_p(wd_margin, WDT_START);

    spin_unlock(&ibwdt_lock);
}

static void ibwdt_disable(void)
{
    spin_lock(&ibwdt_lock);
    outb_p(0, WDT_STOP);
    spin_unlock(&ibwdt_lock);
}

static int ibwdt_set_heartbeat(int t)
{
    if (t < 0 || t > 30)
        return -EINVAL;

    timeout = t;
    return 0;
}

/*
 *  /dev/watchdog handling
 */

static ssize_t ibwdt_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;
            }
        }
        ibwdt_ping();
    }
    return count;
}

static long ibwdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    int new_margin;
    void __user *argp = (void __user *)arg;
    int __user *p = argp;

    static const struct watchdog_info ident = {
        .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
                            | WDIOF_MAGICCLOSE,
        .firmware_version = 1,
        .identity = "IB700 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) {
            ibwdt_disable();
            retval = 0;
        }
        if (options & WDIOS_ENABLECARD) {
            ibwdt_ping();
            retval = 0;
        }
        return retval;
    }
    case WDIOC_KEEPALIVE:
        ibwdt_ping();
        break;

    case WDIOC_SETTIMEOUT:
        if (get_user(new_margin, p))
            return -EFAULT;
        if (ibwdt_set_heartbeat(new_margin))
            return -EINVAL;
        ibwdt_ping();
        /* Fall */

    case WDIOC_GETTIMEOUT:
        return put_user(timeout, p);

    default:
        return -ENOTTY;
    }
    return 0;
}

static int ibwdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(0, &ibwdt_is_open))
        return -EBUSY;
    if (nowayout)
        __module_get(THIS_MODULE);

    /* Activate */
    ibwdt_ping();
    return nonseekable_open(inode, file);
}

static int ibwdt_close(struct inode *inode, struct file *file)
{
    if (expect_close == 42) {
        ibwdt_disable();
    } else {
        pr_crit("WDT device closed unexpectedly.  WDT will not stop!\n");
        ibwdt_ping();
    }
    clear_bit(0, &ibwdt_is_open);
    expect_close = 0;
    return 0;
}

/*
 *  Kernel Interfaces
 */

static const struct file_operations ibwdt_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .write      = ibwdt_write,
    .unlocked_ioctl = ibwdt_ioctl,
    .open       = ibwdt_open,
    .release    = ibwdt_close,
};

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

/*
 *  Init & exit routines
 */

static int __devinit ibwdt_probe(struct platform_device *dev)
{
    int res;

#if WDT_START != WDT_STOP
    if (!request_region(WDT_STOP, 1, "IB700 WDT")) {
        pr_err("STOP method I/O %X is not available\n", WDT_STOP);
        res = -EIO;
        goto out_nostopreg;
    }
#endif

    if (!request_region(WDT_START, 1, "IB700 WDT")) {
        pr_err("START method I/O %X is not available\n", WDT_START);
        res = -EIO;
        goto out_nostartreg;
    }

    /* Check that the heartbeat value is within it's range ;
     * if not reset to the default */
    if (ibwdt_set_heartbeat(timeout)) {
        ibwdt_set_heartbeat(WATCHDOG_TIMEOUT);
        pr_info("timeout value must be 0<=x<=30, using %d\n", timeout);
    }

    res = misc_register(&ibwdt_miscdev);
    if (res) {
        pr_err("failed to register misc device\n");
        goto out_nomisc;
    }
    return 0;

out_nomisc:
    release_region(WDT_START, 1);
out_nostartreg:
#if WDT_START != WDT_STOP
    release_region(WDT_STOP, 1);
#endif
out_nostopreg:
    return res;
}

static int __devexit ibwdt_remove(struct platform_device *dev)
{
    misc_deregister(&ibwdt_miscdev);
    release_region(WDT_START, 1);
#if WDT_START != WDT_STOP
    release_region(WDT_STOP, 1);
#endif
    return 0;
}

static void ibwdt_shutdown(struct platform_device *dev)
{
    /* Turn the WDT off if we have a soft shutdown */
    ibwdt_disable();
}

static struct platform_driver ibwdt_driver = {
    .probe      = ibwdt_probe,
    .remove     = __devexit_p(ibwdt_remove),
    .shutdown   = ibwdt_shutdown,
    .driver     = {
        .owner  = THIS_MODULE,
        .name   = DRV_NAME,
    },
};

static int __init ibwdt_init(void)
{
    int err;

    pr_info("WDT driver for IB700 single board computer initialising\n");

    err = platform_driver_register(&ibwdt_driver);
    if (err)
        return err;

    ibwdt_platform_device = platform_device_register_simple(DRV_NAME,
                                -1, NULL, 0);
    if (IS_ERR(ibwdt_platform_device)) {
        err = PTR_ERR(ibwdt_platform_device);
        goto unreg_platform_driver;
    }

    return 0;

unreg_platform_driver:
    platform_driver_unregister(&ibwdt_driver);
    return err;
}

static void __exit ibwdt_exit(void)
{
    platform_device_unregister(ibwdt_platform_device);
    platform_driver_unregister(&ibwdt_driver);
    pr_info("Watchdog Module Unloaded\n");
}

module_init(ibwdt_init);
module_exit(ibwdt_exit);

MODULE_AUTHOR("Charles Howes <[email protected]>");
MODULE_DESCRIPTION("IB700 SBC watchdog driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

/* end of ib700wdt.c */