udelay.c

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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);