tools/perf/arch/x86/util/tsc.c

   1 #include <stdbool.h>
   2 #include <errno.h>
   3
   4 #include <linux/perf_event.h>
   5
   6 #include "../../perf.h"
   7 #include "../../util/types.h"
   8 #include "../../util/debug.h"
   9 #include "tsc.h"
  10
  11 u64 perf_time_to_tsc(u64 ns, struct perf_tsc_conversion *tc)
  12 {
  13         u64 t, quot, rem;
  14
  15         t = ns - tc->time_zero;
  16         quot = t / tc->time_mult;
  17         rem  = t % tc->time_mult;
  18         return (quot << tc->time_shift) +
  19                (rem << tc->time_shift) / tc->time_mult;
  20 }
  21
  22 u64 tsc_to_perf_time(u64 cyc, struct perf_tsc_conversion *tc)
  23 {
  24         u64 quot, rem;
  25
  26         quot = cyc >> tc->time_shift;
  27         rem  = cyc & ((1 << tc->time_shift) - 1);
  28         return tc->time_zero + quot * tc->time_mult +
  29                ((rem * tc->time_mult) >> tc->time_shift);
  30 }
  31
  32 int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
  33                              struct perf_tsc_conversion *tc)
  34 {
  35         bool cap_user_time_zero;
  36         u32 seq;
  37         int i = 0;
  38
  39         while (1) {
  40                 seq = pc->lock;
  41                 rmb();
  42                 tc->time_mult = pc->time_mult;
  43                 tc->time_shift = pc->time_shift;
  44                 tc->time_zero = pc->time_zero;
  45                 cap_user_time_zero = pc->cap_user_time_zero;
  46                 rmb();
  47                 if (pc->lock == seq && !(seq & 1))
  48                         break;
  49                 if (++i > 10000) {
  50                         pr_debug("failed to get perf_event_mmap_page lock\n");
  51                         return -EINVAL;
  52                 }
  53         }
  54
  55         if (!cap_user_time_zero)
  56                 return -EOPNOTSUPP;
  57
  58         return 0;
  59 }