1 /*
2 * x86 TSC related functions
3 */
4 #ifndef _ASM_X86_TSC_H
5 #define _ASM_X86_TSC_H
6
7 #include <asm/processor.h>
8
9 #define NS_SCALE 10 /* 2^10, carefully chosen */
10 #define US_SCALE 32 /* 2^32, arbitralrily chosen */
11
12 /*
13 * Standard way to access the cycle counter.
14 */
15 typedef unsigned long long cycles_t;
16
17 extern unsigned int cpu_khz;
18 extern unsigned int tsc_khz;
19
get_cycles(void)20 static inline cycles_t get_cycles(void)
21 {
22 unsigned long long ret = 0;
23
24 #ifndef CONFIG_X86_TSC
25 if (!cpu_has_tsc)
26 return 0;
27 #endif
28
29 #if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
30 rdtscll(ret);
31 #endif
32 return ret;
33 }
34
35 /* Like get_cycles, but make sure the CPU is synchronized. */
get_cycles_sync(void)36 static __always_inline cycles_t get_cycles_sync(void)
37 {
38 unsigned long long ret;
39 unsigned eax, edx;
40
41 /*
42 * Use RDTSCP if possible; it is guaranteed to be synchronous
43 * and doesn't cause a VMEXIT on Hypervisors
44 */
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);
49 if (ret)
50 return ret;
51
52 /*
53 * Don't do an additional sync on CPUs where we know
54 * RDTSC is already synchronous:
55 */
56 alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
57 "=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
58 rdtscll(ret);
59
60 return ret;
61 }
62
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);
68
69 /*
70 * Boot-time check whether the TSCs are synchronized across
71 * all CPUs/cores:
72 */
73 extern void check_tsc_sync_source(int cpu);
74 extern void check_tsc_sync_target(void);
75
76 #ifdef CONFIG_X86_64
77 extern void tsc_calibrate(void);
78 #endif
79
80 #endif
81