arch/x86_64/lib/delay.c

   1 /*
   2  *      Precise Delay Loops for x86-64
   3  *
   4  *      Copyright (C) 1993 Linus Torvalds
   5  *      Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   6  *
   7  *      The __delay function must _NOT_ be inlined as its execution time
   8  *      depends wildly on alignment on many x86 processors.
   9  */
  10
  11 #include <linux/config.h>
  12 #include <linux/sched.h>
  13 #include <linux/delay.h>
  14 #include <asm/delay.h>
  15
  16 #ifdef CONFIG_SMP
  17 #include <asm/smp.h>
  18 #endif
  19
  20 int x86_udelay_tsc = 0;         /* Delay via TSC */
  21
  22 void __delay(unsigned long loops)
  23 {
  24         unsigned bclock, now;
  25
  26         rdtscl(bclock);
  27         do
  28         {
  29                 rep_nop();
  30                 rdtscl(now);
  31         }
  32         while((now-bclock) < loops);
  33 }
  34
  35 inline void __const_udelay(unsigned long xloops)
  36 {
  37         __delay(((xloops * cpu_data[_smp_processor_id()].loops_per_jiffy) >> 32) * HZ);
  38 }
  39
  40 void __udelay(unsigned long usecs)
  41 {
  42         __const_udelay(usecs * 0x000010c6);  /* 2**32 / 1000000 */
  43 }
  44
  45 void __ndelay(unsigned long nsecs)
  46 {
  47         __const_udelay(nsecs * 0x00005);  /* 2**32 / 1000000000 (rounded up) */
  48 }