linux/tools/perf/util/tsc.c
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   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
  16u64 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
  27u64 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
  41int 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
  72int 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
 109u64 __weak rdtsc(void)
 110{
 111        return 0;
 112}
 113