udelay.c
1.09 KB
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/*
* Copyright (C) 1993, 2000 Linus Torvalds
*
* Delay routines, using a pre-computed "loops_per_jiffy" value.
*/
#include <linux/module.h>
#include <linux/sched.h> /* for udelay's use of smp_processor_id */
#include <asm/param.h>
#include <asm/smp.h>
#include <linux/delay.h>
/*
* Use only for very small delays (< 1 msec).
*
* The active part of our cycle counter is only 32-bits wide, and
* we're treating the difference between two marks as signed. On
* a 1GHz box, that's about 2 seconds.
*/
void
__delay(int loops)
{
int tmp;
__asm__ __volatile__(
" rpcc %0\n"
" addl %1,%0,%1\n"
"1: rpcc %0\n"
" subl %1,%0,%0\n"
" bgt %0,1b"
: "=&r" (tmp), "=r" (loops) : "1"(loops));
}
#ifdef CONFIG_SMP
#define LPJ cpu_data[smp_processor_id()].loops_per_jiffy
#else
#define LPJ loops_per_jiffy
#endif
void
udelay(unsigned long usecs)
{
usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
__delay((long)usecs >> 32);
}
EXPORT_SYMBOL(udelay);
void
ndelay(unsigned long nsecs)
{
nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
__delay((long)nsecs >> 32);
}
EXPORT_SYMBOL(ndelay);