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 #include <asm/msr.h>
  16
  17 #ifdef CONFIG_SMP
  18 #include <asm/smp.h>
  19 #endif
  20
  21 int x86_udelay_tsc = 0;         /* Delay via TSC */
  22
  23 int read_current_timer(unsigned long *timer_value)
  24 {
  25         rdtscll(*timer_value);
  26         return 0;
  27 }
  28
  29 void __delay(unsigned long loops)
  30 {
  31         unsigned bclock, now;
  32
  33         rdtscl(bclock);
  34         do
  35         {
  36                 rep_nop();
  37                 rdtscl(now);
  38         }
  39         while((now-bclock) < loops);
  40 }
  41
  42 inline void __const_udelay(unsigned long xloops)
  43 {
  44         __delay(((xloops * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32) * HZ);
  45 }
  46
  47 void __udelay(unsigned long usecs)
  48 {
  49         __const_udelay(usecs * 0x000010c6);  /* 2**32 / 1000000 */
  50 }
  51
  52 void __ndelay(unsigned long nsecs)
  53 {
  54         __const_udelay(nsecs * 0x00005);  /* 2**32 / 1000000000 (rounded up) */
  55 }