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/config.h>
   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
  22 void
  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 }
  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
  41 void
  42 udelay(unsigned long usecs)
  43 {
  44         usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
  45         __delay((long)usecs >> 32);
  46 }
  47 EXPORT_SYMBOL(udelay);
  48
  49 void
  50 ndelay(unsigned long nsecs)
  51 {
  52         nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
  53         __delay((long)nsecs >> 32);
  54 }
  55 EXPORT_SYMBOL(ndelay);