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/preempt.h>
  14 #include <linux/delay.h>
  15
  16 #include <asm/delay.h>
  17 #include <asm/msr.h>
  18
  19 #ifdef CONFIG_SMP
  20 #include <asm/smp.h>
  21 #endif
  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         preempt_disable();              /* TSC's are pre-cpu */
  34         rdtscl(bclock);
  35         do {
  36                 rep_nop();
  37                 rdtscl(now);
  38         }
  39         while ((now-bclock) < loops);
  40         preempt_enable();
  41 }
  42 EXPORT_SYMBOL(__delay);
  43
  44 inline void __const_udelay(unsigned long xloops)
  45 {
  46         __delay(((xloops * HZ *
  47                 cpu_data(raw_smp_processor_id()).loops_per_jiffy) >> 32) + 1);
  48 }
  49 EXPORT_SYMBOL(__const_udelay);
  50
  51 void __udelay(unsigned long usecs)
  52 {
  53         __const_udelay(usecs * 0x000010c7);  /* 2**32 / 1000000 (rounded up) */
  54 }
  55 EXPORT_SYMBOL(__udelay);
  56
  57 void __ndelay(unsigned long nsecs)
  58 {
  59         __const_udelay(nsecs * 0x00005);  /* 2**32 / 1000000000 (rounded up) */
  60 }
  61 EXPORT_SYMBOL(__ndelay);