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
  21 void
  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 }
  33
  34 #ifdef CONFIG_SMP
  35 #define LPJ      cpu_data[smp_processor_id()].loops_per_jiffy
  36 #else
  37 #define LPJ      loops_per_jiffy
  38 #endif
  39
  40 void
  41 udelay(unsigned long usecs)
  42 {
  43         usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
  44         __delay((long)usecs >> 32);
  45 }
  46 EXPORT_SYMBOL(udelay);
  47
  48 void
  49 ndelay(unsigned long nsecs)
  50 {
  51         nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
  52         __delay((long)nsecs >> 32);
  53 }
  54 EXPORT_SYMBOL(ndelay);