LinuxQuestions.org - How to use udelay() in uclinux-2.4.x

the file is /usr/src/linux/include/asm-m68k/delay.h and here is the code:
Code:
#ifndef _M68K_DELAY_H

#define _M68K_DELAY_H



#include <asm/param.h>



/*

 * Copyright (C) 1994 Hamish Macdonald

 *

 * Delay routines, using a pre-computed "loops_per_jiffy" value.

 */



static inline void __delay(unsigned long loops)

{

        __asm__ __volatile__ ("1: subql #1,%0; jcc 1b"

                : "=d" (loops) : "0" (loops));

}



extern void __bad_udelay(void);

extern void __bad_ndelay(void);



/*

 * Use only for very small delays ( < 1 msec).  Should probably use a

 * lookup table, really, as the multiplications take much too long with

 * short delays.  This is a "reasonable" implementation, though (and the

 * first constant multiplications gets optimized away if the delay is

 * a constant)  

 */

static inline void __const_udelay(unsigned long xloops)

{

        unsigned long tmp;



        __asm__ ("mulul %2,%0:%1"

                : "=d" (xloops), "=d" (tmp)

                : "d" (xloops), "1" (loops_per_jiffy));

        __delay(xloops * HZ);

}



static inline void __udelay(unsigned long usecs)

{

        __const_udelay(usecs * 4295);  /* 2**32 / 1000000 */

}



static inline void __ndelay(unsigned long nsecs)

{

        __const_udelay(nsecs * 5);      /* 2**32 / 1000000000 */

}



#define udelay(n) (__builtin_constant_p(n) ? \

        ((n) > 20000 ? __bad_udelay() : __const_udelay((n) * 4295)) : \

        __udelay(n))



#define ndelay(n) (__builtin_constant_p(n) ? \

        ((n) > 20000 ? __bad_ndelay() : __const_udelay((n) * 5)) : \

        __ndelay(n))



static inline unsigned long muldiv(unsigned long a, unsigned long b,

                                  unsigned long c)

{

        unsigned long tmp;



        __asm__ ("mulul %2,%0:%1; divul %3,%0:%1"

                : "=d" (tmp), "=d" (a)

                : "d" (b), "d" (c), "1" (a));

        return a;

}



#endif /* defined(_M68K_DELAY_H) */