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delay_64.c

/*
 *    Precise Delay Loops for x86-64
 *
 *    Copyright (C) 1993 Linus Torvalds
 *    Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
 *
 *    The __delay function must _NOT_ be inlined as its execution time
 *    depends wildly on alignment on many x86 processors. 
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/preempt.h>
#include <linux/delay.h>

#include <asm/delay.h>
#include <asm/msr.h>

#ifdef CONFIG_SMP
#include <asm/smp.h>
#endif

int read_current_timer(unsigned long *timer_value)
{
      rdtscll(*timer_value);
      return 0;
}

void __delay(unsigned long loops)
{
      unsigned bclock, now;

      preempt_disable();            /* TSC's are pre-cpu */
      rdtscl(bclock);
      do {
            rep_nop(); 
            rdtscl(now);
      }
      while ((now-bclock) < loops);
      preempt_enable();
}
EXPORT_SYMBOL(__delay);

inline void __const_udelay(unsigned long xloops)
{
      __delay(((xloops * HZ *
            cpu_data(raw_smp_processor_id()).loops_per_jiffy) >> 32) + 1);
}
EXPORT_SYMBOL(__const_udelay);

void __udelay(unsigned long usecs)
{
      __const_udelay(usecs * 0x000010c7);  /* 2**32 / 1000000 (rounded up) */
}
EXPORT_SYMBOL(__udelay);

void __ndelay(unsigned long nsecs)
{
      __const_udelay(nsecs * 0x00005);  /* 2**32 / 1000000000 (rounded up) */
}
EXPORT_SYMBOL(__ndelay);

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