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/processor.h>
  11
  12 #ifdef CONFIG_X86_ELAN
  13 #  define CLOCK_TICK_RATE 1189200 /* AMD Elan has different frequency! */
  14 #else
  15 #  define CLOCK_TICK_RATE 1193182 /* Underlying HZ */
  16 #endif
  17
  18
  19 /*
  20  * Standard way to access the cycle counter on i586+ CPUs.
  21  * Currently only used on SMP.
  22  *
  23  * If you really have a SMP machine with i486 chips or older,
  24  * compile for that, and this will just always return zero.
  25  * That's ok, it just means that the nicer scheduling heuristics
  26  * won't work for you.
  27  *
  28  * We only use the low 32 bits, and we'd simply better make sure
  29  * that we reschedule before that wraps. Scheduling at least every
  30  * four billion cycles just basically sounds like a good idea,
  31  * regardless of how fast the machine is.
  32  */
  33 typedef unsigned long long cycles_t;
  34
  35 static inline cycles_t get_cycles (void)
  36 {
  37         unsigned long long ret=0;
  38
  39 #ifndef CONFIG_X86_TSC
  40         if (!cpu_has_tsc)
  41                 return 0;
  42 #endif
  43
  44 #if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
  45         rdtscll(ret);
  46 #endif
  47         return ret;
  48 }
  49
  50 extern unsigned long cpu_khz;
  51
  52 #endif