patch-2.4.0-test2 linux/drivers/char/sbc60xxwdt.c

• Lines: 339
• Date: Mon Jun 19 13:25:06 2000
• Orig file: v2.4.0-test1/linux/drivers/char/sbc60xxwdt.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.0-test1/linux/drivers/char/sbc60xxwdt.c linux/drivers/char/sbc60xxwdt.c
@@ -0,0 +1,338 @@
+/*
+ *	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
+ *
+ *
+ *  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/malloc.h>
+#include <linux/ioport.h>
+#include <linux/fcntl.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 = 0;
+static int wdt_is_open = 0;
+static int wdt_expect_close = 0;
+
+/*
+ *	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++) 
+			if(buf[ofs] == 'V')
+				wdt_expect_close = 1;
+
+		/* Well, anyhow someone wrote to us, we should return that favour */
+		next_heartbeat = jiffies + WDT_HEARTBEAT;
+	}
+	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)
+{
+	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;
+	return 0;
+}
+
+static long long fop_llseek(struct file *file, long long offset, int origin)
+{
+	return -ESPIPE;
+}
+
+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 -ENOIOCTLCMD;
+		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:		fop_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)