include/asm-i386/tsc.h

   1 /*
   2  * linux/include/asm-i386/tsc.h
   3  *
   4  * i386 TSC related functions
   5  */
   6 #ifndef _ASM_i386_TSC_H
   7 #define _ASM_i386_TSC_H
   8
   9 #include <asm/processor.h>
  10
  11 /*
  12  * Standard way to access the cycle counter.
  13  */
  14 typedef unsigned long long cycles_t;
  15
  16 extern unsigned int cpu_khz;
  17 extern unsigned int tsc_khz;
  18
  19 static inline cycles_t get_cycles(void)
  20 {
  21         unsigned long long ret = 0;
  22
  23 #ifndef CONFIG_X86_TSC
  24         if (!cpu_has_tsc)
  25                 return 0;
  26 #endif
  27
  28 #if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
  29         rdtscll(ret);
  30 #endif
  31         return ret;
  32 }
  33
  34 /* Like get_cycles, but make sure the CPU is synchronized. */
  35 static __always_inline cycles_t get_cycles_sync(void)
  36 {
  37         unsigned long long ret;
  38         unsigned eax, edx;
  39
  40         /*
  41          * Use RDTSCP if possible; it is guaranteed to be synchronous
  42          * and doesn't cause a VMEXIT on Hypervisors
  43          */
  44         alternative_io(ASM_NOP3, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP,
  45                        ASM_OUTPUT2("=a" (eax), "=d" (edx)),
  46                        "a" (0U), "d" (0U) : "ecx", "memory");
  47         ret = (((unsigned long long)edx) << 32) | ((unsigned long long)eax);
  48         if (ret)
  49                 return ret;
  50
  51         /*
  52          * Don't do an additional sync on CPUs where we know
  53          * RDTSC is already synchronous:
  54          */
  55         alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
  56                           "=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
  57         rdtscll(ret);
  58
  59         return ret;
  60 }
  61
  62 extern void tsc_init(void);
  63 extern void mark_tsc_unstable(char *reason);
  64 extern int unsynchronized_tsc(void);
  65 extern void init_tsc_clocksource(void);
  66 int check_tsc_unstable(void);
  67
  68 /*
  69  * Boot-time check whether the TSCs are synchronized across
  70  * all CPUs/cores:
  71  */
  72 extern void check_tsc_sync_source(int cpu);
  73 extern void check_tsc_sync_target(void);
  74
  75 #endif