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From"Bob Zhang" <>
SubjectAbout watch dog timer limit of CPU (Xscale ->IXP425) How can I set more long time ?
DateMon, 4 Dec 2006 13:41:24 +0800
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[unhandled content-type:application/octet-stream]
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