tools/testing/selftests/timers/raw_skew.c

   1 /* CLOCK_MONOTONIC vs CLOCK_MONOTONIC_RAW skew test
   2  *              by: john stultz (johnstul@us.ibm.com)
   3  *                  John Stultz <john.stultz@linaro.org>
   4  *              (C) Copyright IBM 2012
   5  *              (C) Copyright Linaro Limited 2015
   6  *              Licensed under the GPLv2
   7  *
   8  *  To build:
   9  *      $ gcc raw_skew.c -o raw_skew -lrt
  10  *
  11  *   This program is free software: you can redistribute it and/or modify
  12  *   it under the terms of the GNU General Public License as published by
  13  *   the Free Software Foundation, either version 2 of the License, or
  14  *   (at your option) any later version.
  15  *
  16  *   This program is distributed in the hope that it will be useful,
  17  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  *   GNU General Public License for more details.
  20  */
  21
  22 #include <stdio.h>
  23 #include <unistd.h>
  24 #include <stdlib.h>
  25 #include <sys/time.h>
  26 #include <sys/timex.h>
  27 #include <time.h>
  28 #ifdef KTEST
  29 #include "../kselftest.h"
  30 #else
  31 static inline int ksft_exit_pass(void)
  32 {
  33         exit(0);
  34 }
  35 static inline int ksft_exit_fail(void)
  36 {
  37         exit(1);
  38 }
  39 #endif
  40
  41
  42 #define CLOCK_MONOTONIC_RAW             4
  43 #define NSEC_PER_SEC 1000000000LL
  44
  45 #define shift_right(x, s) ({            \
  46         __typeof__(x) __x = (x);        \
  47         __typeof__(s) __s = (s);        \
  48         __x < 0 ? -(-__x >> __s) : __x >> __s; \
  49 })
  50
  51 long long llabs(long long val)
  52 {
  53         if (val < 0)
  54                 val = -val;
  55         return val;
  56 }
  57
  58 unsigned long long ts_to_nsec(struct timespec ts)
  59 {
  60         return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
  61 }
  62
  63 struct timespec nsec_to_ts(long long ns)
  64 {
  65         struct timespec ts;
  66
  67         ts.tv_sec = ns/NSEC_PER_SEC;
  68         ts.tv_nsec = ns%NSEC_PER_SEC;
  69         return ts;
  70 }
  71
  72 long long diff_timespec(struct timespec start, struct timespec end)
  73 {
  74         long long start_ns, end_ns;
  75
  76         start_ns = ts_to_nsec(start);
  77         end_ns = ts_to_nsec(end);
  78         return end_ns - start_ns;
  79 }
  80
  81 void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)
  82 {
  83         struct timespec start, mid, end;
  84         long long diff = 0, tmp;
  85         int i;
  86
  87         for (i = 0; i < 3; i++) {
  88                 long long newdiff;
  89
  90                 clock_gettime(CLOCK_MONOTONIC, &start);
  91                 clock_gettime(CLOCK_MONOTONIC_RAW, &mid);
  92                 clock_gettime(CLOCK_MONOTONIC, &end);
  93
  94                 newdiff = diff_timespec(start, end);
  95                 if (diff == 0 || newdiff < diff) {
  96                         diff = newdiff;
  97                         *raw = mid;
  98                         tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2;
  99                         *mon = nsec_to_ts(tmp);
 100                 }
 101         }
 102 }
 103
 104 int main(int argv, char **argc)
 105 {
 106         struct timespec mon, raw, start, end;
 107         long long delta1, delta2, interval, eppm, ppm;
 108         struct timex tx1, tx2;
 109
 110         setbuf(stdout, NULL);
 111
 112         if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {
 113                 printf("ERR: NO CLOCK_MONOTONIC_RAW\n");
 114                 return -1;
 115         }
 116
 117         tx1.modes = 0;
 118         adjtimex(&tx1);
 119         get_monotonic_and_raw(&mon, &raw);
 120         start = mon;
 121         delta1 = diff_timespec(mon, raw);
 122
 123         if (tx1.offset)
 124                 printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");
 125
 126         printf("Estimating clock drift: ");
 127         sleep(120);
 128
 129         get_monotonic_and_raw(&mon, &raw);
 130         end = mon;
 131         tx2.modes = 0;
 132         adjtimex(&tx2);
 133         delta2 = diff_timespec(mon, raw);
 134
 135         interval = diff_timespec(start, end);
 136
 137         /* calculate measured ppm between MONOTONIC and MONOTONIC_RAW */
 138         eppm = ((delta2-delta1)*NSEC_PER_SEC)/interval;
 139         eppm = -eppm;
 140         printf("%lld.%i(est)", eppm/1000, abs((int)(eppm%1000)));
 141
 142         /* Avg the two actual freq samples adjtimex gave us */
 143         ppm = (tx1.freq + tx2.freq) * 1000 / 2;
 144         ppm = (long long)tx1.freq * 1000;
 145         ppm = shift_right(ppm, 16);
 146         printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
 147
 148         if (llabs(eppm - ppm) > 1000) {
 149                 printf("        [FAILED]\n");
 150                 return ksft_exit_fail();
 151         }
 152         printf("        [OK]\n");
 153         return  ksft_exit_pass();
 154 }