LXR linux/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
  11u64 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
  22u64 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
  32int 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}
  60