2 * linux/include/asm-i386/tsc.h
4 * i386 TSC related functions
6 #ifndef _ASM_i386_TSC_H
7 #define _ASM_i386_TSC_H
9 #include <asm/processor.h>
12 * Standard way to access the cycle counter on i586+ CPUs.
13 * Currently only used on SMP.
15 * If you really have a SMP machine with i486 chips or older,
16 * compile for that, and this will just always return zero.
17 * That's ok, it just means that the nicer scheduling heuristics
20 * We only use the low 32 bits, and we'd simply better make sure
21 * that we reschedule before that wraps. Scheduling at least every
22 * four billion cycles just basically sounds like a good idea,
23 * regardless of how fast the machine is.
25 typedef unsigned long long cycles_t;
27 extern unsigned int cpu_khz;
28 extern unsigned int tsc_khz;
30 static inline cycles_t get_cycles(void)
32 unsigned long long ret = 0;
34 #ifndef CONFIG_X86_TSC
39 #if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
45 extern void tsc_init(void);
46 extern void mark_tsc_unstable(void);