sbc_fitpc2_wdt.c

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/*
 * Watchdog driver for SBC-FITPC2 board
 *
 * Author: Denis Turischev <[email protected]>
 *
 * Adapted from the IXP2000 watchdog driver by Deepak Saxena.
 *
 * This file is licensed under  the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#define pr_fmt(fmt) KBUILD_MODNAME " WATCHDOG: " fmt

#include <linux/module.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/ioport.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/dmi.h>
#include <linux/io.h>
#include <linux/uaccess.h>


static bool nowayout = WATCHDOG_NOWAYOUT;
static unsigned int margin = 60;    /* (secs) Default is 1 minute */
static unsigned long wdt_status;
static DEFINE_MUTEX(wdt_lock);

#define WDT_IN_USE      0
#define WDT_OK_TO_CLOSE     1

#define COMMAND_PORT        0x4c
#define DATA_PORT       0x48

#define IFACE_ON_COMMAND    1
#define REBOOT_COMMAND      2

#define WATCHDOG_NAME       "SBC-FITPC2 Watchdog"

static void wdt_send_data(unsigned char command, unsigned char data)
{
    outb(data, DATA_PORT);
    msleep(200);
    outb(command, COMMAND_PORT);
    msleep(100);
}

static void wdt_enable(void)
{
    mutex_lock(&wdt_lock);
    wdt_send_data(IFACE_ON_COMMAND, 1);
    wdt_send_data(REBOOT_COMMAND, margin);
    mutex_unlock(&wdt_lock);
}

static void wdt_disable(void)
{
    mutex_lock(&wdt_lock);
    wdt_send_data(IFACE_ON_COMMAND, 0);
    wdt_send_data(REBOOT_COMMAND, 0);
    mutex_unlock(&wdt_lock);
}

static int fitpc2_wdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(WDT_IN_USE, &wdt_status))
        return -EBUSY;

    clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

    wdt_enable();

    return nonseekable_open(inode, file);
}

static ssize_t fitpc2_wdt_write(struct file *file, const char *data,
                        size_t len, loff_t *ppos)
{
    size_t i;

    if (!len)
        return 0;

    if (nowayout) {
        len = 0;
        goto out;
    }

    clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

    for (i = 0; i != len; i++) {
        char c;

        if (get_user(c, data + i))
            return -EFAULT;

        if (c == 'V')
            set_bit(WDT_OK_TO_CLOSE, &wdt_status);
    }

out:
    wdt_enable();

    return len;
}


static const struct watchdog_info ident = {
    .options    = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT |
                WDIOF_KEEPALIVEPING,
    .identity   = WATCHDOG_NAME,
};


static long fitpc2_wdt_ioctl(struct file *file, unsigned int cmd,
                            unsigned long arg)
{
    int ret = -ENOTTY;
    int time;

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        ret = copy_to_user((struct watchdog_info *)arg, &ident,
                   sizeof(ident)) ? -EFAULT : 0;
        break;

    case WDIOC_GETSTATUS:
        ret = put_user(0, (int *)arg);
        break;

    case WDIOC_GETBOOTSTATUS:
        ret = put_user(0, (int *)arg);
        break;

    case WDIOC_KEEPALIVE:
        wdt_enable();
        ret = 0;
        break;

    case WDIOC_SETTIMEOUT:
        ret = get_user(time, (int *)arg);
        if (ret)
            break;

        if (time < 31 || time > 255) {
            ret = -EINVAL;
            break;
        }

        margin = time;
        wdt_enable();
        /* Fall through */

    case WDIOC_GETTIMEOUT:
        ret = put_user(margin, (int *)arg);
        break;
    }

    return ret;
}

static int fitpc2_wdt_release(struct inode *inode, struct file *file)
{
    if (test_bit(WDT_OK_TO_CLOSE, &wdt_status)) {
        wdt_disable();
        pr_info("Device disabled\n");
    } else {
        pr_warn("Device closed unexpectedly - timer will not stop\n");
        wdt_enable();
    }

    clear_bit(WDT_IN_USE, &wdt_status);
    clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

    return 0;
}


static const struct file_operations fitpc2_wdt_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .write      = fitpc2_wdt_write,
    .unlocked_ioctl = fitpc2_wdt_ioctl,
    .open       = fitpc2_wdt_open,
    .release    = fitpc2_wdt_release,
};

static struct miscdevice fitpc2_wdt_miscdev = {
    .minor      = WATCHDOG_MINOR,
    .name       = "watchdog",
    .fops       = &fitpc2_wdt_fops,
};

static int __init fitpc2_wdt_init(void)
{
    int err;
    const char *brd_name;

    brd_name = dmi_get_system_info(DMI_BOARD_NAME);

    if (!brd_name || !strstr(brd_name, "SBC-FITPC2"))
        return -ENODEV;

    pr_info("%s found\n", brd_name);

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

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

    if (margin < 31 || margin > 255) {
        pr_err("margin must be in range 31 - 255 seconds, you tried to set %d\n",
               margin);
        err = -EINVAL;
        goto err_margin;
    }

    err = misc_register(&fitpc2_wdt_miscdev);
    if (err) {
        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
               WATCHDOG_MINOR, err);
        goto err_margin;
    }

    return 0;

err_margin:
    release_region(DATA_PORT, 1);
err_data_port:
    release_region(COMMAND_PORT, 1);

    return err;
}

static void __exit fitpc2_wdt_exit(void)
{
    misc_deregister(&fitpc2_wdt_miscdev);
    release_region(DATA_PORT, 1);
    release_region(COMMAND_PORT, 1);
}

module_init(fitpc2_wdt_init);
module_exit(fitpc2_wdt_exit);

MODULE_AUTHOR("Denis Turischev <[email protected]>");
MODULE_DESCRIPTION("SBC-FITPC2 Watchdog");

module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds (default 60s)");

module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");

MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);