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

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (C) 1993, 2000 Linus Torvalds
   4 *
   5 * Delay routines, using a pre-computed "loops_per_jiffy" value.
   6 */
   7
   8#include <linux/module.h>
   9#include <linux/sched.h> /* for udelay's use of smp_processor_id */
  10#include <asm/param.h>
  11#include <asm/smp.h>
  12#include <linux/delay.h>
  13
  14/*
  15 * Use only for very small delays (< 1 msec). 
  16 *
  17 * The active part of our cycle counter is only 32-bits wide, and
  18 * we're treating the difference between two marks as signed.  On
  19 * a 1GHz box, that's about 2 seconds.
  20 */
  21
  22void
  23__delay(int loops)
  24{
  25        int tmp;
  26        __asm__ __volatile__(
  27                "       rpcc %0\n"
  28                "       addl %1,%0,%1\n"
  29                "1:     rpcc %0\n"
  30                "       subl %1,%0,%0\n"
  31                "       bgt %0,1b"
  32                : "=&r" (tmp), "=r" (loops) : "1"(loops));
  33}
  34EXPORT_SYMBOL(__delay);
  35
  36#ifdef CONFIG_SMP
  37#define LPJ      cpu_data[smp_processor_id()].loops_per_jiffy
  38#else
  39#define LPJ      loops_per_jiffy
  40#endif
  41
  42void
  43udelay(unsigned long usecs)
  44{
  45        usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
  46        __delay((long)usecs >> 32);
  47}
  48EXPORT_SYMBOL(udelay);
  49
  50void
  51ndelay(unsigned long nsecs)
  52{
  53        nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
  54        __delay((long)nsecs >> 32);
  55}
  56EXPORT_SYMBOL(ndelay);
  57