patch-2.4.19 linux-2.4.19/drivers/char/sc520_wdt.c

• Lines: 382
• Date: Fri Aug 2 17:39:43 2002
• Orig file: linux-2.4.18/drivers/char/sc520_wdt.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.18/drivers/char/sc520_wdt.c linux-2.4.19/drivers/char/sc520_wdt.c
@@ -0,0 +1,381 @@
+/*
+ *	AMD Elan SC520 processor Watchdog Timer driver for Linux 2.4.x
+ *
+ *      Based on acquirewdt.c by Alan Cox,
+ *           and sbc60xxwdt.c by Jakob Oestergaard <jakob@ostenfeld.dk>
+ *     
+ *	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 authors do 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 2001    Scott Jennings <linuxdrivers@oro.net>
+ *           9/27 - 2001      [Initial release]
+ *	
+ *	Additional fixes Alan Cox
+ *	-	Fixed formatting
+ *	-	Removed debug printks
+ *	-	Fixed SMP built kernel deadlock
+ *	-	Switched to private locks not lock_kernel
+ *	-	Used ioremap/writew/readw
+ *	-	Added NOWAYOUT 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 most other Linux WDT
+ *  drivers in that the driver will ping the watchdog by itself,
+ *  because this particular WDT has a very short timeout (1.6
+ *  seconds) and it would be insane to count on any userspace
+ *  daemon always getting scheduled within that time frame.
+ *
+ *  This driver uses memory mapped IO, and spinlock.
+ */
+
+#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>
+
+/*
+ * The SC520 can timeout anywhere from 492us to 32.21s.
+ * 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 30 seconds.
+ */
+
+#define WDT_HEARTBEAT (HZ * 30)
+
+/*
+ * AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
+ *
+ *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
+ *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
+ */
+
+#define TIMEOUT_EXPONENT ( 1 << 3 )  /* 0x08 = 2.01s */
+
+/* #define MMCR_BASE_DEFAULT 0xfffef000 */
+#define MMCR_BASE_DEFAULT ((__u16 *)0xffffe)
+#define OFFS_WDTMRCTL ((unsigned int)0xcb0)
+#define WDT_ENB 0x8000		/* [15] Watchdog Timer Enable */
+#define WDT_WRST_ENB 0x4000	/* [14] Watchdog Timer Reset Enable */
+
+#define OUR_NAME "sc520_wdt"
+
+#define WRT_DOG(data) *wdtmrctl=data
+
+static __u16 *wdtmrctl;
+
+static void wdt_timer_ping(unsigned long);
+static struct timer_list timer;
+static unsigned long next_heartbeat;
+static unsigned long wdt_is_open;
+static int wdt_expect_close;
+
+static spinlock_t wdt_spinlock;
+/*
+ *	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 */
+		spin_lock(&wdt_spinlock);
+		writew(0xAAAA, wdtmrctl);
+		writew(0x5555, wdtmrctl);
+		spin_unlock(&wdt_spinlock);
+
+		/* 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_config(int writeval)
+{
+	__u16 dummy;
+	unsigned long flags;
+
+	/* buy some time (ping) */
+	spin_lock_irqsave(&wdt_spinlock, flags);
+	dummy=readw(wdtmrctl);  /* ensure write synchronization */
+	writew(0xAAAA, wdtmrctl);
+	writew(0x5555, wdtmrctl);
+	/* make WDT configuration register writable one time */
+	writew(0x3333, wdtmrctl);
+	writew(0xCCCC, wdtmrctl);
+	/* write WDT configuration register */
+	writew(writeval, wdtmrctl);
+	spin_unlock_irqrestore(&wdt_spinlock, flags);
+}
+
+static void wdt_startup(void)
+{
+	next_heartbeat = jiffies + WDT_HEARTBEAT;
+
+	/* Start the timer */
+	timer.expires = jiffies + WDT_INTERVAL;	
+	add_timer(&timer);
+
+	wdt_config(WDT_ENB | WDT_WRST_ENB | TIMEOUT_EXPONENT);
+	printk(OUR_NAME ": Watchdog timer is now enabled.\n");  
+}
+
+static void wdt_turnoff(void)
+{
+#ifndef CONFIG_WATCHDOG_NOWAYOUT
+	/* Stop the timer */
+	del_timer(&timer);
+	wdt_config(0);
+	printk(OUR_NAME ": Watchdog timer is now disabled...\n");
+#endif
+}
+
+
+/*
+ * /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 1;
+	}
+	return 0;
+}
+
+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(test_and_set_bit(0, &wdt_is_open))
+				return -EBUSY;
+			/* Good, fire up the show */
+			wdt_startup();
+#ifdef CONFIG_WATCHDOG_NOWAYOUT
+			MOD_INC_USE_COUNT;
+#endif	
+			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");
+		}
+	}
+	clear_bit(0, &wdt_is_open);
+	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,
+		"SC520"
+	};
+	
+	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,
+	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 sc520_wdt_unload(void)
+{
+	wdt_turnoff();
+
+	/* Deregister */
+	misc_deregister(&wdt_miscdev);
+	iounmap(wdtmrctl);
+	unregister_reboot_notifier(&wdt_notifier);
+}
+
+static int __init sc520_wdt_init(void)
+{
+	int rc = -EBUSY;
+	unsigned long cbar;
+
+	spin_lock_init(&wdt_spinlock);
+
+	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;
+
+	/* get the Base Address Register */
+	cbar = inl_p(0xfffc);
+	printk(OUR_NAME ": CBAR: 0x%08lx\n", cbar);
+	/* check if MMCR aliasing bit is set */
+	if (cbar & 0x80000000) {
+		printk(OUR_NAME ": MMCR Aliasing enabled.\n");
+		wdtmrctl = (__u16 *)(cbar & 0x3fffffff);
+	} else {
+		printk(OUR_NAME "!!! WARNING !!!\n"
+		  "\t MMCR Aliasing found NOT enabled!\n"
+		  "\t Using default value of: %p\n"
+		  "\t This has not been tested!\n"
+		  "\t Please email Scott Jennings <smj@oro.net>\n"
+		  "\t  and Bill Jennings <bj@oro.net> if it works!\n"
+		  , MMCR_BASE_DEFAULT
+		  );
+	  wdtmrctl = MMCR_BASE_DEFAULT;
+	}
+
+	wdtmrctl = (__u16 *)((char *)wdtmrctl + OFFS_WDTMRCTL);
+	wdtmrctl = ioremap((unsigned long)wdtmrctl, 2);
+	printk(KERN_INFO OUR_NAME ": WDT driver for SC520 initialised.\n");
+
+	return 0;
+
+err_out_miscdev:
+	misc_deregister(&wdt_miscdev);
+err_out_region2:
+	return rc;
+}
+
+module_init(sc520_wdt_init);
+module_exit(sc520_wdt_unload);
+
+MODULE_AUTHOR("Scott and Bill Jennings");
+MODULE_DESCRIPTION("Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
+MODULE_LICENSE("GPL");
+EXPORT_NO_SYMBOLS;