2 * x86 TSC related functions
7 #include <asm/processor.h>
9 #define NS_SCALE 10 /* 2^10, carefully chosen */
10 #define US_SCALE 32 /* 2^32, arbitralrily chosen */
13 * Standard way to access the cycle counter.
15 typedef unsigned long long cycles_t
;
17 extern unsigned int cpu_khz
;
18 extern unsigned int tsc_khz
;
20 static inline cycles_t
get_cycles(void)
22 unsigned long long ret
= 0;
24 #ifndef CONFIG_X86_TSC
29 #if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
35 /* Like get_cycles, but make sure the CPU is synchronized. */
36 static __always_inline cycles_t
get_cycles_sync(void)
38 unsigned long long ret
;
42 * Use RDTSCP if possible; it is guaranteed to be synchronous
43 * and doesn't cause a VMEXIT on Hypervisors
45 alternative_io(ASM_NOP3
, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP
,
46 ASM_OUTPUT2("=a" (eax
), "=d" (edx
)),
47 "a" (0U), "d" (0U) : "ecx", "memory");
48 ret
= (((unsigned long long)edx
) << 32) | ((unsigned long long)eax
);
53 * Don't do an additional sync on CPUs where we know
54 * RDTSC is already synchronous:
56 alternative_io("cpuid", ASM_NOP2
, X86_FEATURE_SYNC_RDTSC
,
57 "=a" (eax
), "0" (1) : "ebx","ecx","edx","memory");
63 extern void tsc_init(void);
64 extern void mark_tsc_unstable(char *reason
);
65 extern int unsynchronized_tsc(void);
66 extern void init_tsc_clocksource(void);
67 int check_tsc_unstable(void);
70 * Boot-time check whether the TSCs are synchronized across
73 extern void check_tsc_sync_source(int cpu
);
74 extern void check_tsc_sync_target(void);
77 extern void tsc_calibrate(void);