tools/perf/util/tsc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <errno.h>
   3
   4 #include <linux/compiler.h>
   5 #include <linux/perf_event.h>
   6 #include <linux/stddef.h>
   7 #include <linux/types.h>
   8
   9 #include <asm/barrier.h>
  10
  11 #include "event.h"
  12 #include "synthetic-events.h"
  13 #include "debug.h"
  14 #include "tsc.h"
  15
  16 u64 perf_time_to_tsc(u64 ns, struct perf_tsc_conversion *tc)
  17 {
  18         u64 t, quot, rem;
  19
  20         t = ns - tc->time_zero;
  21         quot = t / tc->time_mult;
  22         rem  = t % tc->time_mult;
  23         return (quot << tc->time_shift) +
  24                (rem << tc->time_shift) / tc->time_mult;
  25 }
  26
  27 u64 tsc_to_perf_time(u64 cyc, struct perf_tsc_conversion *tc)
  28 {
  29         u64 quot, rem;
  30
  31         if (tc->cap_user_time_short)
  32                 cyc = tc->time_cycles +
  33                         ((cyc - tc->time_cycles) & tc->time_mask);
  34
  35         quot = cyc >> tc->time_shift;
  36         rem  = cyc & (((u64)1 << tc->time_shift) - 1);
  37         return tc->time_zero + quot * tc->time_mult +
  38                ((rem * tc->time_mult) >> tc->time_shift);
  39 }
  40
  41 int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
  42                              struct perf_tsc_conversion *tc)
  43 {
  44         u32 seq;
  45         int i = 0;
  46
  47         while (1) {
  48                 seq = pc->lock;
  49                 rmb();
  50                 tc->time_mult = pc->time_mult;
  51                 tc->time_shift = pc->time_shift;
  52                 tc->time_zero = pc->time_zero;
  53                 tc->time_cycles = pc->time_cycles;
  54                 tc->time_mask = pc->time_mask;
  55                 tc->cap_user_time_zero = pc->cap_user_time_zero;
  56                 tc->cap_user_time_short = pc->cap_user_time_short;
  57                 rmb();
  58                 if (pc->lock == seq && !(seq & 1))
  59                         break;
  60                 if (++i > 10000) {
  61                         pr_debug("failed to get perf_event_mmap_page lock\n");
  62                         return -EINVAL;
  63                 }
  64         }
  65
  66         if (!tc->cap_user_time_zero)
  67                 return -EOPNOTSUPP;
  68
  69         return 0;
  70 }
  71
  72 int perf_event__synth_time_conv(const struct perf_event_mmap_page *pc,
  73                                 struct perf_tool *tool,
  74                                 perf_event__handler_t process,
  75                                 struct machine *machine)
  76 {
  77         union perf_event event = {
  78                 .time_conv = {
  79                         .header = {
  80                                 .type = PERF_RECORD_TIME_CONV,
  81                                 .size = sizeof(struct perf_record_time_conv),
  82                         },
  83                 },
  84         };
  85         struct perf_tsc_conversion tc;
  86         int err;
  87
  88         if (!pc)
  89                 return 0;
  90         err = perf_read_tsc_conversion(pc, &tc);
  91         if (err == -EOPNOTSUPP)
  92                 return 0;
  93         if (err)
  94                 return err;
  95
  96         pr_debug2("Synthesizing TSC conversion information\n");
  97
  98         event.time_conv.time_mult  = tc.time_mult;
  99         event.time_conv.time_shift = tc.time_shift;
 100         event.time_conv.time_zero  = tc.time_zero;
 101         event.time_conv.time_cycles = tc.time_cycles;
 102         event.time_conv.time_mask = tc.time_mask;
 103         event.time_conv.cap_user_time_zero = tc.cap_user_time_zero;
 104         event.time_conv.cap_user_time_short = tc.cap_user_time_short;
 105
 106         return process(tool, &event, NULL, machine);
 107 }
 108
 109 u64 __weak rdtsc(void)
 110 {
 111         return 0;
 112 }