LXR linux/arch/alpha/lib/udelay.c

   1/*
   2 * Copyright (C) 1993, 2000 Linus Torvalds
   3 *
   4 * Delay routines, using a pre-computed "loops_per_jiffy" value.
   5 */
   6
   7#include <linux/module.h>
   8#include <linux/sched.h> /* for udelay's use of smp_processor_id */
   9#include <asm/param.h>
  10#include <asm/smp.h>
  11#include <linux/delay.h>
  12
  13/*
  14 * Use only for very small delays (< 1 msec). 
  15 *
  16 * The active part of our cycle counter is only 32-bits wide, and
  17 * we're treating the difference between two marks as signed.  On
  18 * a 1GHz box, that's about 2 seconds.
  19 */
  20
  21void
  22__delay(int loops)
  23{
  24        int tmp;
  25        __asm__ __volatile__(
  26                "       rpcc %0\n"
  27                "       addl %1,%0,%1\n"
  28                "1:     rpcc %0\n"
  29                "       subl %1,%0,%0\n"
  30                "       bgt %0,1b"
  31                : "=&r" (tmp), "=r" (loops) : "1"(loops));
  32}
  33EXPORT_SYMBOL(__delay);
  34
  35#ifdef CONFIG_SMP
  36#define LPJ      cpu_data[smp_processor_id()].loops_per_jiffy
  37#else
  38#define LPJ      loops_per_jiffy
  39#endif
  40
  41void
  42udelay(unsigned long usecs)
  43{
  44        usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
  45        __delay((long)usecs >> 32);
  46}
  47EXPORT_SYMBOL(udelay);
  48
  49void
  50ndelay(unsigned long nsecs)
  51{
  52        nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
  53        __delay((long)nsecs >> 32);
  54}
  55EXPORT_SYMBOL(ndelay);
  56