arch/x86/lib/delay_64.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/module.h>
  12 #include <linux/sched.h>
  13 #include <linux/timex.h>
  14 #include <linux/preempt.h>
  15 #include <linux/delay.h>
  16 #include <linux/init.h>
  17
  18 #include <asm/delay.h>
  19 #include <asm/msr.h>
  20
  21 #ifdef CONFIG_SMP
  22 #include <asm/smp.h>
  23 #endif
  24
  25 int __devinit read_current_timer(unsigned long *timer_value)
  26 {
  27         rdtscll(*timer_value);
  28         return 0;
  29 }
  30
  31 void __delay(unsigned long loops)
  32 {
  33         unsigned bclock, now;
  34
  35         preempt_disable();              /* TSC's are pre-cpu */
  36         rdtscl(bclock);
  37         do {
  38                 rep_nop();
  39                 rdtscl(now);
  40         }
  41         while ((now-bclock) < loops);
  42         preempt_enable();
  43 }
  44 EXPORT_SYMBOL(__delay);
  45
  46 inline void __const_udelay(unsigned long xloops)
  47 {
  48         __delay(((xloops * HZ *
  49                 cpu_data(raw_smp_processor_id()).loops_per_jiffy) >> 32) + 1);
  50 }
  51 EXPORT_SYMBOL(__const_udelay);
  52
  53 void __udelay(unsigned long usecs)
  54 {
  55         __const_udelay(usecs * 0x000010c7);  /* 2**32 / 1000000 (rounded up) */
  56 }
  57 EXPORT_SYMBOL(__udelay);
  58
  59 void __ndelay(unsigned long nsecs)
  60 {
  61         __const_udelay(nsecs * 0x00005);  /* 2**32 / 1000000000 (rounded up) */
  62 }
  63 EXPORT_SYMBOL(__ndelay);