i386/linux-2.3.21/include/asm-i386/timex.h

   1 /*
   2  * linux/include/asm-i386/timex.h
   3  *
   4  * i386 architecture timex specifications
   5  */
   6 #ifndef _ASMi386_TIMEX_H
   7 #define _ASMi386_TIMEX_H
   8
   9 #include <linux/config.h>
  10 #include <asm/msr.h>
  11
  12 #define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
  13 #define CLOCK_TICK_FACTOR       20      /* Factor of both 1000000 and CLOCK_TICK_RATE */
  14 #define FINETUNE ((((((long)LATCH * HZ - CLOCK_TICK_RATE) << SHIFT_HZ) * \
  15         (1000000/CLOCK_TICK_FACTOR) / (CLOCK_TICK_RATE/CLOCK_TICK_FACTOR)) \
  16                 << (SHIFT_SCALE-SHIFT_HZ)) / HZ)
  17
  18 /*
  19  * Standard way to access the cycle counter on i586+ CPUs.
  20  * Currently only used on SMP.
  21  *
  22  * If you really have a SMP machine with i486 chips or older,
  23  * compile for that, and this will just always return zero.
  24  * That's ok, it just means that the nicer scheduling heuristics
  25  * won't work for you.
  26  *
  27  * We only use the low 32 bits, and we'd simply better make sure
  28  * that we reschedule before that wraps. Scheduling at least every
  29  * four billion cycles just basically sounds like a good idea,
  30  * regardless of how fast the machine is.
  31  */
  32 typedef unsigned long cycles_t;
  33
  34 extern cycles_t cacheflush_time;
  35
  36 static inline cycles_t get_cycles (void)
  37 {
  38 #ifndef CONFIG_X86_TSC
  39         return 0;
  40 #else
  41         unsigned long eax, edx;
  42
  43         rdtsc(eax,edx);
  44         return eax;
  45 #endif
  46 }
  47
  48 #endif