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/*
* 60xx Single Board Computer Watchdog Timer driver for Linux 2.2.x
*
* Based on acquirewdt.c by Alan Cox.
*
* 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.
*
* The author does NOT admit liability nor provide warranty for
* any of this software. This material is provided "AS-IS" in
* the hope that it may be useful for others.
*
* (c) Copyright 2000 Jakob Oestergaard <jakob@ostenfeld.dk>
*
* 12/4 - 2000 [Initial revision]
* 25/4 - 2000 Added /dev/watchdog support
* 09/5 - 2001 [smj@oro.net] fixed fop_write to "return 1" on success
*
*
* Theory of operation:
* A Watchdog Timer (WDT) is a hardware circuit that can
* reset the computer system in case of a software fault.
* You probably knew that already.
*
* Usually a userspace daemon will notify the kernel WDT driver
* via the /proc/watchdog special device file that userspace is
* still alive, at regular intervals. When such a notification
* occurs, the driver will usually tell the hardware watchdog
* that everything is in order, and that the watchdog should wait
* for yet another little while to reset the system.
* If userspace fails (RAM error, kernel bug, whatever), the
* notifications cease to occur, and the hardware watchdog will
* reset the system (causing a reboot) after the timeout occurs.
*
* This WDT driver is different from the other Linux WDT
* drivers in several ways:
* *) The driver will ping the watchdog by itself, because this
* particular WDT has a very short timeout (one second) and it
* would be insane to count on any userspace daemon always
* getting scheduled within that time frame.
* *) This driver expects the userspace daemon to send a specific
* character code ('V') to /dev/watchdog before closing the
* /dev/watchdog file. If the userspace daemon closes the file
* without sending this special character, the driver will assume
* that the daemon (and userspace in general) died, and will
* stop pinging the WDT without disabling it first. This will
* cause a reboot.
*
* Why `V' ? Well, `V' is the character in ASCII for the value 86,
* and we all know that 86 is _the_ most random number in the universe.
* Therefore it is the letter that has the slightest chance of occuring
* by chance, when the system becomes corrupted.
*
*/
#include <linux/module.h>
#include <linux/version.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/sched.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/fcntl.h>
#include <linux/smp_lock.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#define OUR_NAME "sbc60xxwdt"
/*
* You must set these - The driver cannot probe for the settings
*/
#define WDT_STOP 0x45
#define WDT_START 0x443
/*
* The 60xx board can use watchdog timeout values from one second
* to several minutes. The default is one second, so if we reset
* the watchdog every ~250ms we should be safe.
*/
#define WDT_INTERVAL (HZ/4+1)
/*
* We must not require too good response from the userspace daemon.
* Here we require the userspace daemon to send us a heartbeat
* char to /dev/watchdog every 10 seconds.
* If the daemon pulses us every 5 seconds, we can still afford
* a 5 second scheduling delay on the (high priority) daemon. That
* should be sufficient for a box under any load.
*/
#define WDT_HEARTBEAT (HZ * 10)
static void wdt_timer_ping(unsigned long);
static struct timer_list timer;
static unsigned long next_heartbeat;
static int wdt_is_open;
static int wdt_expect_close;
/*
* Whack the dog
*/
static void wdt_timer_ping(unsigned long data)
{
/* If we got a heartbeat pulse within the WDT_US_INTERVAL
* we agree to ping the WDT
*/
if(time_before(jiffies, next_heartbeat))
{
/* Ping the WDT by reading from WDT_START */
inb_p(WDT_START);
/* Re-set the timer interval */
timer.expires = jiffies + WDT_INTERVAL;
add_timer(&timer);
} else {
printk(OUR_NAME ": Heartbeat lost! Will not ping the watchdog\n");
}
}
/*
* Utility routines
*/
static void wdt_startup(void)
{
next_heartbeat = jiffies + WDT_HEARTBEAT;
/* Start the timer */
timer.expires = jiffies + WDT_INTERVAL;
add_timer(&timer);
printk(OUR_NAME ": Watchdog timer is now enabled.\n");
}
static void wdt_turnoff(void)
{
/* Stop the timer */
del_timer(&timer);
inb_p(WDT_STOP);
printk(OUR_NAME ": Watchdog timer is now disabled...\n");
}
/*
* /dev/watchdog handling
*/
static ssize_t fop_write(struct file * file, const char * buf, size_t count, loff_t * ppos)
{
/* We can't seek */
if(ppos != &file->f_pos)
return -ESPIPE;
/* See if we got the magic character */
if(count)
{
size_t ofs;
/* note: just in case someone wrote the magic character
* five months ago... */
wdt_expect_close = 0;
/* now scan */
for(ofs = 0; ofs != count; ofs++)
{
char c;
if(get_user(c, buf+ofs))
return -EFAULT;
if(c == 'V')
wdt_expect_close = 1;
}
/* Well, anyhow someone wrote to us, we should return that favour */
next_heartbeat = jiffies + WDT_HEARTBEAT;
return 1;
}
return 0;
}
static ssize_t fop_read(struct file * file, char * buf, size_t count, loff_t * ppos)
{
/* No can do */
return -EINVAL;
}
static int fop_open(struct inode * inode, struct file * file)
{
switch(MINOR(inode->i_rdev))
{
case WATCHDOG_MINOR:
/* Just in case we're already talking to someone... */
if(wdt_is_open)
return -EBUSY;
/* Good, fire up the show */
wdt_is_open = 1;
wdt_startup();
return 0;
default:
return -ENODEV;
}
}
static int fop_close(struct inode * inode, struct file * file)
{
lock_kernel();
if(MINOR(inode->i_rdev) == WATCHDOG_MINOR)
{
if(wdt_expect_close)
wdt_turnoff();
else {
del_timer(&timer);
printk(OUR_NAME ": device file closed unexpectedly. Will not stop the WDT!\n");
}
}
wdt_is_open = 0;
unlock_kernel();
return 0;
}
static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
unsigned long arg)
{
static struct watchdog_info ident=
{
0,
1,
"SB60xx"
};
switch(cmd)
{
default:
return -ENOTTY;
case WDIOC_GETSUPPORT:
return copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident))?-EFAULT:0;
case WDIOC_KEEPALIVE:
next_heartbeat = jiffies + WDT_HEARTBEAT;
return 0;
}
}
static struct file_operations wdt_fops = {
owner: THIS_MODULE,
llseek: no_llseek,
read: fop_read,
write: fop_write,
open: fop_open,
release: fop_close,
ioctl: fop_ioctl
};
static struct miscdevice wdt_miscdev = {
WATCHDOG_MINOR,
"watchdog",
&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_turnoff();
return NOTIFY_DONE;
}
/*
* The WDT needs to learn about soft shutdowns in order to
* turn the timebomb registers off.
*/
static struct notifier_block wdt_notifier=
{
wdt_notify_sys,
0,
0
};
static void __exit sbc60xxwdt_unload(void)
{
wdt_turnoff();
/* Deregister */
misc_deregister(&wdt_miscdev);
unregister_reboot_notifier(&wdt_notifier);
release_region(WDT_START,1);
release_region(WDT_STOP,1);
}
static int __init sbc60xxwdt_init(void)
{
int rc = -EBUSY;
if (!request_region(WDT_STOP, 1, "SBC 60XX WDT"))
goto err_out;
if (!request_region(WDT_START, 1, "SBC 60XX WDT"))
goto err_out_region1;
init_timer(&timer);
timer.function = wdt_timer_ping;
timer.data = 0;
rc = misc_register(&wdt_miscdev);
if (rc)
goto err_out_region2;
rc = register_reboot_notifier(&wdt_notifier);
if (rc)
goto err_out_miscdev;
printk(KERN_INFO OUR_NAME ": WDT driver for 60XX single board computer initialised.\n");
return 0;
err_out_miscdev:
misc_deregister(&wdt_miscdev);
err_out_region2:
release_region(WDT_START,1);
err_out_region1:
release_region(WDT_STOP,1);
err_out:
return rc;
}
module_init(sbc60xxwdt_init);
module_exit(sbc60xxwdt_unload);
MODULE_LICENSE("GPL");
EXPORT_NO_SYMBOLS;
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