at91rm9200_wdt.c

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/*
 * Watchdog driver for Atmel AT91RM9200 (Thunder)
 *
 *  Copyright (C) 2003 SAN People (Pty) Ltd
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>
#include <mach/at91_st.h>

#define WDT_DEFAULT_TIME    5   /* seconds */
#define WDT_MAX_TIME        256 /* seconds */

static int wdt_time = WDT_DEFAULT_TIME;
static bool nowayout = WATCHDOG_NOWAYOUT;

module_param(wdt_time, int, 0);
MODULE_PARM_DESC(wdt_time, "Watchdog time in seconds. (default="
                __MODULE_STRING(WDT_DEFAULT_TIME) ")");

#ifdef CONFIG_WATCHDOG_NOWAYOUT
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
        "Watchdog cannot be stopped once started (default="
                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
#endif


static unsigned long at91wdt_busy;

/* ......................................................................... */

/*
 * Disable the watchdog.
 */
static inline void at91_wdt_stop(void)
{
    at91_st_write(AT91_ST_WDMR, AT91_ST_EXTEN);
}

/*
 * Enable and reset the watchdog.
 */
static inline void at91_wdt_start(void)
{
    at91_st_write(AT91_ST_WDMR, AT91_ST_EXTEN | AT91_ST_RSTEN |
                (((65536 * wdt_time) >> 8) & AT91_ST_WDV));
    at91_st_write(AT91_ST_CR, AT91_ST_WDRST);
}

/*
 * Reload the watchdog timer.  (ie, pat the watchdog)
 */
static inline void at91_wdt_reload(void)
{
    at91_st_write(AT91_ST_CR, AT91_ST_WDRST);
}

/* ......................................................................... */

/*
 * Watchdog device is opened, and watchdog starts running.
 */
static int at91_wdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(0, &at91wdt_busy))
        return -EBUSY;

    at91_wdt_start();
    return nonseekable_open(inode, file);
}

/*
 * Close the watchdog device.
 * If CONFIG_WATCHDOG_NOWAYOUT is NOT defined then the watchdog is also
 *  disabled.
 */
static int at91_wdt_close(struct inode *inode, struct file *file)
{
    /* Disable the watchdog when file is closed */
    if (!nowayout)
        at91_wdt_stop();

    clear_bit(0, &at91wdt_busy);
    return 0;
}

/*
 * Change the watchdog time interval.
 */
static int at91_wdt_settimeout(int new_time)
{
    /*
     * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
     *
     * Since WDV is a 16-bit counter, the maximum period is
     * 65536 / 256 = 256 seconds.
     */
    if ((new_time <= 0) || (new_time > WDT_MAX_TIME))
        return -EINVAL;

    /* Set new watchdog time. It will be used when
       at91_wdt_start() is called. */
    wdt_time = new_time;
    return 0;
}

static const struct watchdog_info at91_wdt_info = {
    .identity   = "at91 watchdog",
    .options    = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
};

/*
 * Handle commands from user-space.
 */
static long at91_wdt_ioctl(struct file *file,
                    unsigned int cmd, unsigned long arg)
{
    void __user *argp = (void __user *)arg;
    int __user *p = argp;
    int new_value;

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        return copy_to_user(argp, &at91_wdt_info,
                sizeof(at91_wdt_info)) ? -EFAULT : 0;
    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, p);
    case WDIOC_SETOPTIONS:
        if (get_user(new_value, p))
            return -EFAULT;
        if (new_value & WDIOS_DISABLECARD)
            at91_wdt_stop();
        if (new_value & WDIOS_ENABLECARD)
            at91_wdt_start();
        return 0;
    case WDIOC_KEEPALIVE:
        at91_wdt_reload();  /* pat the watchdog */
        return 0;
    case WDIOC_SETTIMEOUT:
        if (get_user(new_value, p))
            return -EFAULT;
        if (at91_wdt_settimeout(new_value))
            return -EINVAL;
        /* Enable new time value */
        at91_wdt_start();
        /* Return current value */
        return put_user(wdt_time, p);
    case WDIOC_GETTIMEOUT:
        return put_user(wdt_time, p);
    default:
        return -ENOTTY;
    }
}

/*
 * Pat the watchdog whenever device is written to.
 */
static ssize_t at91_wdt_write(struct file *file, const char *data,
                        size_t len, loff_t *ppos)
{
    at91_wdt_reload();      /* pat the watchdog */
    return len;
}

/* ......................................................................... */

static const struct file_operations at91wdt_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .unlocked_ioctl = at91_wdt_ioctl,
    .open       = at91_wdt_open,
    .release    = at91_wdt_close,
    .write      = at91_wdt_write,
};

static struct miscdevice at91wdt_miscdev = {
    .minor      = WATCHDOG_MINOR,
    .name       = "watchdog",
    .fops       = &at91wdt_fops,
};

static int __devinit at91wdt_probe(struct platform_device *pdev)
{
    int res;

    if (at91wdt_miscdev.parent)
        return -EBUSY;
    at91wdt_miscdev.parent = &pdev->dev;

    res = misc_register(&at91wdt_miscdev);
    if (res)
        return res;

    pr_info("AT91 Watchdog Timer enabled (%d seconds%s)\n",
        wdt_time, nowayout ? ", nowayout" : "");
    return 0;
}

static int __devexit at91wdt_remove(struct platform_device *pdev)
{
    int res;

    res = misc_deregister(&at91wdt_miscdev);
    if (!res)
        at91wdt_miscdev.parent = NULL;

    return res;
}

static void at91wdt_shutdown(struct platform_device *pdev)
{
    at91_wdt_stop();
}

#ifdef CONFIG_PM

static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
{
    at91_wdt_stop();
    return 0;
}

static int at91wdt_resume(struct platform_device *pdev)
{
    if (at91wdt_busy)
        at91_wdt_start();
    return 0;
}

#else
#define at91wdt_suspend NULL
#define at91wdt_resume  NULL
#endif

static struct platform_driver at91wdt_driver = {
    .probe      = at91wdt_probe,
    .remove     = __devexit_p(at91wdt_remove),
    .shutdown   = at91wdt_shutdown,
    .suspend    = at91wdt_suspend,
    .resume     = at91wdt_resume,
    .driver     = {
        .name   = "at91_wdt",
        .owner  = THIS_MODULE,
    },
};

static int __init at91_wdt_init(void)
{
    /* Check that the heartbeat value is within range;
       if not reset to the default */
    if (at91_wdt_settimeout(wdt_time)) {
        at91_wdt_settimeout(WDT_DEFAULT_TIME);
        pr_info("wdt_time value must be 1 <= wdt_time <= 256, using %d\n",
            wdt_time);
    }

    return platform_driver_register(&at91wdt_driver);
}

static void __exit at91_wdt_exit(void)
{
    platform_driver_unregister(&at91wdt_driver);
}

module_init(at91_wdt_init);
module_exit(at91_wdt_exit);

MODULE_AUTHOR("Andrew Victor");
MODULE_DESCRIPTION("Watchdog driver for Atmel AT91RM9200");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS("platform:at91_wdt");