/release/src/linux/linux/drivers/char/sbc60xxwdt.c
C | 346 lines | 190 code | 46 blank | 110 comment | 20 complexity | 4c7f6748cfdc4c7cfe702de6c7db166f MD5 | raw file
- /*
- * 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=
- {
- WDIOF_MAGICCLOSE,
- 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;
- // We cannot reserve 0x45 - the kernel already has!
- // 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;