src/include/cpu/x86/tsc.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #ifndef CPU_X86_TSC_H
   4 #define CPU_X86_TSC_H
   5
   6 #include <stdint.h>
   7
   8 #if CONFIG(TSC_SYNC_MFENCE)
   9 #define TSC_SYNC "mfence\n"
  10 #elif CONFIG(TSC_SYNC_LFENCE)
  11 #define TSC_SYNC "lfence\n"
  12 #else
  13 #define TSC_SYNC
  14 #endif
  15
  16 struct tsc_struct {
  17         unsigned int lo;
  18         unsigned int hi;
  19 };
  20 typedef struct tsc_struct tsc_t;
  21
  22 static inline tsc_t rdtsc(void)
  23 {
  24         tsc_t res;
  25         asm volatile (
  26                 TSC_SYNC
  27                 "rdtsc"
  28                 : "=a" (res.lo), "=d"(res.hi) /* outputs */
  29         );
  30         return res;
  31 }
  32
  33 /* Simple 32- to 64-bit multiplication. Uses 16-bit words to avoid overflow.
  34  * This code is used to prevent use of libgcc's umoddi3.
  35  */
  36 static inline void multiply_to_tsc(tsc_t *const tsc, const u32 a, const u32 b)
  37 {
  38         tsc->lo = (a & 0xffff) * (b & 0xffff);
  39         tsc->hi = ((tsc->lo >> 16)
  40                 + ((a & 0xffff) * (b >> 16))
  41                 + ((b & 0xffff) * (a >> 16)));
  42         tsc->lo = ((tsc->hi & 0xffff) << 16) | (tsc->lo & 0xffff);
  43         tsc->hi = ((a >> 16) * (b >> 16)) + (tsc->hi >> 16);
  44 }
  45
  46 static inline uint64_t tsc_to_uint64(tsc_t tstamp)
  47 {
  48         return (((uint64_t)tstamp.hi) << 32) + tstamp.lo;
  49 }
  50
  51 static inline unsigned long long rdtscll(void)
  52 {
  53         return tsc_to_uint64(rdtsc());
  54 }
  55
  56 /* Provided by CPU/chipset code for the TSC rate in MHz. */
  57 unsigned long tsc_freq_mhz(void);
  58
  59 static inline int tsc_constant_rate(void)
  60 {
  61         return !CONFIG(UNKNOWN_TSC_RATE);
  62 }
  63
  64 #endif /* CPU_X86_TSC_H */