sbc7240_wdt.c

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/*
 *  NANO7240 SBC Watchdog device driver
 *
 *  Based on w83877f.c by Scott Jennings,
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation;
 *
 *  Software distributed under the License is distributed on an "AS IS"
 *  basis, WITHOUT WARRANTY OF ANY KIND, either express or
 *  implied. See the License for the specific language governing
 *  rights and limitations under the License.
 *
 *  (c) Copyright 2007  Gilles GIGAN <[email protected]>
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/miscdevice.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/atomic.h>

#define SBC7240_ENABLE_PORT     0x443
#define SBC7240_DISABLE_PORT        0x043
#define SBC7240_SET_TIMEOUT_PORT    SBC7240_ENABLE_PORT
#define SBC7240_MAGIC_CHAR      'V'

#define SBC7240_TIMEOUT     30
#define SBC7240_MAX_TIMEOUT     255
static int timeout = SBC7240_TIMEOUT;   /* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. (1<=timeout<="
         __MODULE_STRING(SBC7240_MAX_TIMEOUT) ", default="
         __MODULE_STRING(SBC7240_TIMEOUT) ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Disable watchdog when closing device file");

#define SBC7240_OPEN_STATUS_BIT     0
#define SBC7240_ENABLED_STATUS_BIT  1
#define SBC7240_EXPECT_CLOSE_STATUS_BIT 2
static unsigned long wdt_status;

/*
 * Utility routines
 */

static void wdt_disable(void)
{
    /* disable the watchdog */
    if (test_and_clear_bit(SBC7240_ENABLED_STATUS_BIT, &wdt_status)) {
        inb_p(SBC7240_DISABLE_PORT);
        pr_info("Watchdog timer is now disabled\n");
    }
}

static void wdt_enable(void)
{
    /* enable the watchdog */
    if (!test_and_set_bit(SBC7240_ENABLED_STATUS_BIT, &wdt_status)) {
        inb_p(SBC7240_ENABLE_PORT);
        pr_info("Watchdog timer is now enabled\n");
    }
}

static int wdt_set_timeout(int t)
{
    if (t < 1 || t > SBC7240_MAX_TIMEOUT) {
        pr_err("timeout value must be 1<=x<=%d\n", SBC7240_MAX_TIMEOUT);
        return -1;
    }
    /* set the timeout */
    outb_p((unsigned)t, SBC7240_SET_TIMEOUT_PORT);
    timeout = t;
    pr_info("timeout set to %d seconds\n", t);
    return 0;
}

/* Whack the dog */
static inline void wdt_keepalive(void)
{
    if (test_bit(SBC7240_ENABLED_STATUS_BIT, &wdt_status))
        inb_p(SBC7240_ENABLE_PORT);
}

/*
 * /dev/watchdog handling
 */
static ssize_t fop_write(struct file *file, const char __user *buf,
             size_t count, loff_t *ppos)
{
    size_t i;
    char c;

    if (count) {
        if (!nowayout) {
            clear_bit(SBC7240_EXPECT_CLOSE_STATUS_BIT,
                &wdt_status);

            /* is there a magic char ? */
            for (i = 0; i != count; i++) {
                if (get_user(c, buf + i))
                    return -EFAULT;
                if (c == SBC7240_MAGIC_CHAR) {
                    set_bit(SBC7240_EXPECT_CLOSE_STATUS_BIT,
                        &wdt_status);
                    break;
                }
            }
        }

        wdt_keepalive();
    }

    return count;
}

static int fop_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(SBC7240_OPEN_STATUS_BIT, &wdt_status))
        return -EBUSY;

    wdt_enable();

    return nonseekable_open(inode, file);
}

static int fop_close(struct inode *inode, struct file *file)
{
    if (test_and_clear_bit(SBC7240_EXPECT_CLOSE_STATUS_BIT, &wdt_status)
        || !nowayout) {
        wdt_disable();
    } else {
        pr_crit("Unexpected close, not stopping watchdog!\n");
        wdt_keepalive();
    }

    clear_bit(SBC7240_OPEN_STATUS_BIT, &wdt_status);
    return 0;
}

static const struct watchdog_info ident = {
    .options = WDIOF_KEEPALIVEPING|
           WDIOF_SETTIMEOUT|
           WDIOF_MAGICCLOSE,
    .firmware_version = 1,
    .identity = "SBC7240",
};


static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    switch (cmd) {
    case WDIOC_GETSUPPORT:
        return copy_to_user((void __user *)arg, &ident, sizeof(ident))
                         ? -EFAULT : 0;
    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, (int __user *)arg);
    case WDIOC_SETOPTIONS:
    {
        int options;
        int retval = -EINVAL;

        if (get_user(options, (int __user *)arg))
            return -EFAULT;

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

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

        return retval;
    }
    case WDIOC_KEEPALIVE:
        wdt_keepalive();
        return 0;
    case WDIOC_SETTIMEOUT:
    {
        int new_timeout;

        if (get_user(new_timeout, (int __user *)arg))
            return -EFAULT;

        if (wdt_set_timeout(new_timeout))
            return -EINVAL;

        /* Fall through */
    }
    case WDIOC_GETTIMEOUT:
        return put_user(timeout, (int __user *)arg);
    default:
        return -ENOTTY;
    }
}

static const struct file_operations wdt_fops = {
    .owner = THIS_MODULE,
    .llseek = no_llseek,
    .write = fop_write,
    .open = fop_open,
    .release = fop_close,
    .unlocked_ioctl = fop_ioctl,
};

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

/*
 *  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();
    return NOTIFY_DONE;
}

static struct notifier_block wdt_notifier = {
    .notifier_call = wdt_notify_sys,
};

static void __exit sbc7240_wdt_unload(void)
{
    pr_info("Removing watchdog\n");
    misc_deregister(&wdt_miscdev);

    unregister_reboot_notifier(&wdt_notifier);
    release_region(SBC7240_ENABLE_PORT, 1);
}

static int __init sbc7240_wdt_init(void)
{
    int rc = -EBUSY;

    if (!request_region(SBC7240_ENABLE_PORT, 1, "SBC7240 WDT")) {
        pr_err("I/O address 0x%04x already in use\n",
               SBC7240_ENABLE_PORT);
        rc = -EIO;
        goto err_out;
    }

    /* The IO port 0x043 used to disable the watchdog
     * is already claimed by the system timer, so we
     * can't request_region() it ...*/

    if (timeout < 1 || timeout > SBC7240_MAX_TIMEOUT) {
        timeout = SBC7240_TIMEOUT;
        pr_info("timeout value must be 1<=x<=%d, using %d\n",
            SBC7240_MAX_TIMEOUT, timeout);
    }
    wdt_set_timeout(timeout);
    wdt_disable();

    rc = register_reboot_notifier(&wdt_notifier);
    if (rc) {
        pr_err("cannot register reboot notifier (err=%d)\n", rc);
        goto err_out_region;
    }

    rc = misc_register(&wdt_miscdev);
    if (rc) {
        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
               wdt_miscdev.minor, rc);
        goto err_out_reboot_notifier;
    }

    pr_info("Watchdog driver for SBC7240 initialised (nowayout=%d)\n",
        nowayout);

    return 0;

err_out_reboot_notifier:
    unregister_reboot_notifier(&wdt_notifier);
err_out_region:
    release_region(SBC7240_ENABLE_PORT, 1);
err_out:
    return rc;
}

module_init(sbc7240_wdt_init);
module_exit(sbc7240_wdt_unload);

MODULE_AUTHOR("Gilles Gigan");
MODULE_DESCRIPTION("Watchdog device driver for single board"
           " computers EPIC Nano 7240 from iEi");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);