| /* |
| * 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; |
| |
| #ifdef CONFIG_WATCHDOG_NOWAYOUT |
| static int nowayout = 1; |
| #else |
| static int nowayout = 0; |
| #endif |
| |
| MODULE_PARM(nowayout,"i"); |
| MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)"); |
| |
| /* |
| * 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; |
| if (nowayout) { |
| MOD_INC_USE_COUNT; |
| } |
| /* 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) |
| { |
| if(minor(inode->i_rdev) == WATCHDOG_MINOR) |
| { |
| if(wdt_expect_close && !nowayout) |
| wdt_turnoff(); |
| else { |
| del_timer(&timer); |
| printk(OUR_NAME ": device file closed unexpectedly. Will not stop the WDT!\n"); |
| } |
| } |
| wdt_is_open = 0; |
| 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; |