About watch dog timer limit of CPU (Xscale ->IXP425) How can I set more long time ?

["Bob Zhang" <zhanglinbao@gmail.com>]

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Hello all , 

    My embeded board hardware configuration is like this :
# cat /proc/cpuinfo
Processor       : XScale-IXP425/IXC1100 rev 1 (v5b)
BogoMIPS        : 266.24
Features        : swp half thumb fastmult edsp 

Hardware        : Intel IXDP425 Development Platform
Revision        : 0000
Serial          : 0000000000000000

Through reading datasheet of ixp4xx ,I know it has own watchdog functions ,
please see attchment :15 Timer 

I find a driver by goole , 
see attachment .


Watchdog timer counter is 32 bit register , its max value is 2<<32 -1 

#define TIMER_FREQ 66000000 /* 66 MHZ timer */
#define TIMER_KEY 0x482e
#define TIMER_MARGIN 60  /* (secs) Default is 1 minute */     
//I want to modify it ,I find its max value is 65

static int ixp425_margin = TIMER_MARGIN; /* in seconds */
static int ixp425wdt_users;
//static int pre_margin;  //IXP425 CPU 's watch dog timer is 32 bit , 
//so I define it to be unsigned int --bob
static unsigned int pre_margin;   
pre_margin = TIMER_FREQ *  TIMER_MARGIN 
*IXP425_OSWT = pre_margin; 

if I need one minutes , 
*IXP425_OSWT = 66000000 * 60 =  396000000  ,not overflow  

if I need two minutes , 
*IXP425_OSWT = 66000000 * 120 = 792000000  ( which has been >  2<<32-1  , overflow 

So I compute the max time I can set :
 T_max = 2<<32-1 / 66000000    =  65 seconds 。  


--------------------
My question:

if need more seconds ( for example , 5 minutes ) ,what should I do ? 

I have a method based on datasheet (ixp4xx) ,but I don't know if it will successed when system crash 

How can I do to break the limit of hardware ? 
Thanks ahead ! 

--
Best Regards
bob

[-- Attachment #2: ixp425_wdt.c --]
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/*
 *	Watchdog driver for the IXP2400/IXP2800 based platforms
 *
 *      (c) Copyright 2000 Intel Coporation
 *          Based on SoftDog driver by Alan Cox <alan@redhat.com>
 *
 *	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.
 *
 *	Neither Oleg Drokin nor iXcelerator.com admit liability nor provide
 *	warranty for any of this software. This material is provided
 *	"AS-IS" and at no charge.
 *
 *	Harold Yang <harold.yang@intel.com>
 *	Stanley Wang <stanley.wang@intel.com>
 *
 */

#include <linux/module.h>
#include <linux/config.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/reboot.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <asm/hardware.h>
#include <asm/bitops.h>
#include <asm/arch/ixp425.h>

#define MY_NAME "IXP425 Watchdog Timer"

/* you must define it ,otherwise ,the timer will stop after write() ,read()  */
//#define CONFIG_WATCHDOG_NOWAYOUT

/* you can comment it ,if you don't debug */
#define CONFIG_IXP425_WTDEBUG

#ifdef CONFIG_IXP425_WTDEBUG
#define dbg(format, arg...)                                     \
	do {                                                    \
		printk("<0>" "%s: " format,		\
				MY_NAME , ## arg);              \
        } while (0)
#else
#define dbg(format, arg...)
#endif

#define TIMER_FREQ	66000000	/* 66 MHZ timer */
#define TIMER_KEY	0x482e
#define TIMER_MARGIN	66		/* (secs) Default is 1 minute */

static int ixp425_margin = TIMER_MARGIN;	/* in seconds */
static int ixp425wdt_users;
//static int pre_margin;  //IXP425 CPU 's watch dog timer is 32 bit , so I define it to be unsigned int --bob
static unsigned int pre_margin;

/*
 *	Allow only one person to hold it open
 */

static int ixp425dog_open(struct inode *inode, struct file *file)
{
	if(test_and_set_bit(1,&ixp425wdt_users))
		return -EBUSY;
	MOD_INC_USE_COUNT;
	dbg("\n\nin open () function  , *IXP425_OSWT = %u\n",*IXP425_OSWT);
	dbg("ixp425_margin=%d\n",ixp425_margin);
	/* Activate IXP425 Watchdog timer */
	pre_margin=TIMER_FREQ * ixp425_margin;
	*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
	*IXP425_OSWT = pre_margin;	
	dbg("in open function pre_margin = %u\n",pre_margin);
	*IXP425_OSWE = 0x5;  //bit 0:reset ; bit 1:interupt; bit 2:counter down enable 
	*IXP425_OSWK = 0;		/* Lock the watch dog timer */
	return 0;
}

static int ixp425dog_release(struct inode *inode, struct file *file)
{
	/*
	 *	Shut off the timer.
	 * 	Lock it in if it's a module and we defined ...NOWAYOUT
	 */
	*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
	*IXP425_OSWT = pre_margin;
#ifndef CONFIG_WATCHDOG_NOWAYOUT
	*IXP425_OSWE = 0x0;
#endif
	*IXP425_OSWK = 0;		/* Lock the watch dog timer */
	ixp425wdt_users = 0;
	MOD_DEC_USE_COUNT;
	return 0;
}

static ssize_t ixp425dog_write(struct file *file, const char *data, size_t len, loff_t *ppos)
{
	/*  Can't seek (pwrite) on this device  */
	if (ppos != &file->f_pos)
		return -ESPIPE;

	/* Refresh OSMR3 timer. */
	if(len) {
		dbg("has into write function len !=0  , *IXP425_OSWT = %u\n",*IXP425_OSWT);
		dbg("just IXP425_OSWT will set to be %u \n",pre_margin);
		*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
		*IXP425_OSWT = pre_margin;
		*IXP425_OSWK = 0;		/* Lock the watch dog timer */
		return 1;
	}
	return 0;
}

/* it is only used to test the IXP425_OSWT register's value 
  --BOB */
static ssize_t ixp425dog_read(struct file *file, char *data, size_t len, loff_t *ppos)
{
	
	/* read OSMR3 timer. */
	int current_timer = 0;
	char buffer[10] = {'\0'};
	
	dbg("has into read() function  , *IXP425_OSWT = %u\n",*IXP425_OSWT);
	//*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
	current_timer = *IXP425_OSWT ;
	//*IXP425_OSWK = 0;		/* Lock the watch dog timer */
	//-->
	snprintf(buffer,sizeof(buffer)-1,"%d",current_timer);
	copy_to_user(data,buffer,strlen(buffer));
	
}



static int ixp425dog_ioctl(struct inode *inode, struct file *file,
	unsigned int cmd, unsigned long arg)
{
	int new_margin;
	int options = 0;
	static struct watchdog_info ident = {
		identity: "IXP425 Watchdog Timer",
		options: WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_CARDRESET,
	};

	switch(cmd){
	default:
		return -ENOIOCTLCMD;
	case WDIOC_GETSUPPORT:
		return copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident));
	case WDIOC_GETSTATUS:
		return put_user(0,(int *)arg);
	case WDIOC_GETBOOTSTATUS:
		return put_user((*IXP425_OSST & 0x00000010) ? WDIOF_CARDRESET : 0, (int *)arg);
	case WDIOC_GETTEMP:
		return -ENOIOCTLCMD;
	case WDIOC_SETOPTIONS:
		if (get_user(options, (int *)arg))
			return -EFAULT;
		switch(options) {
			case WDIOS_DISABLECARD:
				*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
				*IXP425_OSWE = 0x0; 
				*IXP425_OSWK = 0;		/* Lock the watch dog timer */
				return 0;
			case WDIOS_ENABLECARD:
				*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
				*IXP425_OSWE = 0x5; 
				*IXP425_OSWK = 0;		/* Lock the watch dog timer */
				return 0;
			default:	
				return -ENOIOCTLCMD;		
		}
	case WDIOC_SETTIMEOUT:
		if (get_user(new_margin, (int *)arg))
			return -EFAULT;
		if (new_margin < 1)
			return -EINVAL;
		ixp425_margin = new_margin;
		pre_margin=TIMER_FREQ * ixp425_margin;
		*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
		*IXP425_OSWT = pre_margin;
		*IXP425_OSWK = 0;		/* Lock the watch dog timer */
		return 0;
	case WDIOC_GETTIMEOUT:
		put_user(ixp425_margin, (int *)arg);
		return 0;
	case WDIOC_KEEPALIVE:
		*IXP425_OSWK = TIMER_KEY; 	/* Unlock the watch dog timer */
		*IXP425_OSWT = pre_margin;
		*IXP425_OSWK = 0;		/* Lock the watch dog timer */
		return 0;
	}
}

static struct file_operations ixp425dog_fops=
{
	owner:		THIS_MODULE,
	read:		ixp425dog_read,
	write:		ixp425dog_write,
	ioctl:		ixp425dog_ioctl,
	open:		ixp425dog_open,
	release:	ixp425dog_release,
};

static struct miscdevice ixp425dog_miscdev=
{
	WATCHDOG_MINOR,
	"IXP425 watchdog",
	&ixp425dog_fops
};

static int __init ixp425dog_init(void)
{
	int ret;
	dbg("WATCHDOG_MINOR = %d\n",WATCHDOG_MINOR);
	ret = misc_register(&ixp425dog_miscdev);
	dbg("ret of misc_register() = %d\n",ret);	
	if (ret)
		return ret;

	dbg("timer margin %d sec\n", ixp425_margin);

	return 0;
}

static void __exit ixp425dog_exit(void)
{
	misc_deregister(&ixp425dog_miscdev);
}

module_init(ixp425dog_init);
module_exit(ixp425dog_exit);

MODULE_AUTHOR("Stanely Wang");
MODULE_LICENSE("GPL");
MODULE_PARM(ixp425_margin,"i");
MODULE_PARM_DESC(ixp425_margin,"IXP425 Watchdog Timer's expiring time.");
MODULE_DESCRIPTION("IXP425 Watchdog Timer driver.");
MODULE_SUPPORTED_DEVICE("IXCDP1100 dev board.");