patch-2.2.16 linux/drivers/char/sbc60xxwdt.c

• Lines: 305
• Date: Wed Jun 7 14:26:42 2000
• Orig file: v2.2.15/linux/drivers/char/sbc60xxwdt.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN v2.2.15/linux/drivers/char/sbc60xxwdt.c linux/drivers/char/sbc60xxwdt.c
@@ -0,0 +1,304 @@
+/*
+ *	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/config.h>
+#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 = { 0, 0, WDT_INTERVAL, 0, wdt_timer_ping };
+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 */
+
+    MOD_INC_USE_COUNT;
+
+    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;
+
+  MOD_DEC_USE_COUNT;
+  return 0;
+}
+
+
+static struct file_operations wdt_fops = {
+  0,
+  fop_read,
+  fop_write,
+  0,  /* readdir */
+  0,  /* select */
+  0,  /* ioctl */
+  0,  /* mmap */
+  fop_open,
+  0,  /* flush */
+  fop_close
+};
+
+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
+};
+
+#ifdef MODULE
+
+#define sbc60xxwdt_init init_module
+
+void cleanup_module(void)
+{
+  wdt_turnoff();
+
+  /* Deregister */
+
+  misc_deregister(&wdt_miscdev);
+
+  unregister_reboot_notifier(&wdt_notifier);
+
+  release_region(WDT_STOP,1);
+  release_region(WDT_START,1);
+}
+
+#endif
+
+__initfunc(int sbc60xxwdt_init(void))
+{
+  printk(OUR_NAME ": WDT driver for 60XX single board computer initialising.\n");
+
+  misc_register(&wdt_miscdev);
+
+  request_region(WDT_STOP, 1, "SBC 60XX WDT");
+  request_region(WDT_START, 1, "SBC 60XX WDT");
+  register_reboot_notifier(&wdt_notifier);
+
+  return 0;
+}
+