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 read_current_timer(unsigned long *timer_value)
  22 {
  23         rdtscll(*timer_value);
  24         return 0;
  25 }
  26
  27 void __delay(unsigned long loops)
  28 {
  29         unsigned bclock, now;
  30
  31         rdtscl(bclock);
  32         do
  33         {
  34                 rep_nop();
  35                 rdtscl(now);
  36         }
  37         while((now-bclock) < loops);
  38 }
  39
  40 inline void __const_udelay(unsigned long xloops)
  41 {
  42         __delay(((xloops * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32) * HZ);
  43 }
  44
  45 void __udelay(unsigned long usecs)
  46 {
  47         __const_udelay(usecs * 0x000010c6);  /* 2**32 / 1000000 */
  48 }
  49
  50 void __ndelay(unsigned long nsecs)
  51 {
  52         __const_udelay(nsecs * 0x00005);  /* 2**32 / 1000000000 (rounded up) */
  53 }