tools/testing/selftests/timers/freq-step.c

   1 /*
   2  * This test checks the response of the system clock to frequency
   3  * steps made with adjtimex(). The frequency error and stability of
   4  * the CLOCK_MONOTONIC clock relative to the CLOCK_MONOTONIC_RAW clock
   5  * is measured in two intervals following the step. The test fails if
   6  * values from the second interval exceed specified limits.
   7  *
   8  * Copyright (C) Miroslav Lichvar <mlichvar@redhat.com>  2017
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of version 2 of the GNU General Public License as
  12  * published by the Free Software Foundation.
  13  *
  14  * This program is distributed in the hope that it will be useful, but
  15  * WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * General Public License for more details.
  18  */
  19
  20 #include <math.h>
  21 #include <stdio.h>
  22 #include <sys/timex.h>
  23 #include <time.h>
  24 #include <unistd.h>
  25
  26 #include "../kselftest.h"
  27
  28 #define SAMPLES 100
  29 #define SAMPLE_READINGS 10
  30 #define MEAN_SAMPLE_INTERVAL 0.1
  31 #define STEP_INTERVAL 1.0
  32 #define MAX_PRECISION 100e-9
  33 #define MAX_FREQ_ERROR 10e-6
  34 #define MAX_STDDEV 1000e-9
  35
  36 #ifndef ADJ_SETOFFSET
  37   #define ADJ_SETOFFSET 0x0100
  38 #endif
  39
  40 struct sample {
  41         double offset;
  42         double time;
  43 };
  44
  45 static time_t mono_raw_base;
  46 static time_t mono_base;
  47 static long user_hz;
  48 static double precision;
  49 static double mono_freq_offset;
  50
  51 static double diff_timespec(struct timespec *ts1, struct timespec *ts2)
  52 {
  53         return ts1->tv_sec - ts2->tv_sec + (ts1->tv_nsec - ts2->tv_nsec) / 1e9;
  54 }
  55
  56 static double get_sample(struct sample *sample)
  57 {
  58         double delay, mindelay = 0.0;
  59         struct timespec ts1, ts2, ts3;
  60         int i;
  61
  62         for (i = 0; i < SAMPLE_READINGS; i++) {
  63                 clock_gettime(CLOCK_MONOTONIC_RAW, &ts1);
  64                 clock_gettime(CLOCK_MONOTONIC, &ts2);
  65                 clock_gettime(CLOCK_MONOTONIC_RAW, &ts3);
  66
  67                 ts1.tv_sec -= mono_raw_base;
  68                 ts2.tv_sec -= mono_base;
  69                 ts3.tv_sec -= mono_raw_base;
  70
  71                 delay = diff_timespec(&ts3, &ts1);
  72                 if (delay <= 1e-9) {
  73                         i--;
  74                         continue;
  75                 }
  76
  77                 if (!i || delay < mindelay) {
  78                         sample->offset = diff_timespec(&ts2, &ts1);
  79                         sample->offset -= delay / 2.0;
  80                         sample->time = ts1.tv_sec + ts1.tv_nsec / 1e9;
  81                         mindelay = delay;
  82                 }
  83         }
  84
  85         return mindelay;
  86 }
  87
  88 static void reset_ntp_error(void)
  89 {
  90         struct timex txc;
  91
  92         txc.modes = ADJ_SETOFFSET;
  93         txc.time.tv_sec = 0;
  94         txc.time.tv_usec = 0;
  95
  96         if (adjtimex(&txc) < 0) {
  97                 perror("[FAIL] adjtimex");
  98                 ksft_exit_fail();
  99         }
 100 }
 101
 102 static void set_frequency(double freq)
 103 {
 104         struct timex txc;
 105         int tick_offset;
 106
 107         tick_offset = 1e6 * freq / user_hz;
 108
 109         txc.modes = ADJ_TICK | ADJ_FREQUENCY;
 110         txc.tick = 1000000 / user_hz + tick_offset;
 111         txc.freq = (1e6 * freq - user_hz * tick_offset) * (1 << 16);
 112
 113         if (adjtimex(&txc) < 0) {
 114                 perror("[FAIL] adjtimex");
 115                 ksft_exit_fail();
 116         }
 117 }
 118
 119 static void regress(struct sample *samples, int n, double *intercept,
 120                     double *slope, double *r_stddev, double *r_max)
 121 {
 122         double x, y, r, x_sum, y_sum, xy_sum, x2_sum, r2_sum;
 123         int i;
 124
 125         x_sum = 0.0, y_sum = 0.0, xy_sum = 0.0, x2_sum = 0.0;
 126
 127         for (i = 0; i < n; i++) {
 128                 x = samples[i].time;
 129                 y = samples[i].offset;
 130
 131                 x_sum += x;
 132                 y_sum += y;
 133                 xy_sum += x * y;
 134                 x2_sum += x * x;
 135         }
 136
 137         *slope = (xy_sum - x_sum * y_sum / n) / (x2_sum - x_sum * x_sum / n);
 138         *intercept = (y_sum - *slope * x_sum) / n;
 139
 140         *r_max = 0.0, r2_sum = 0.0;
 141
 142         for (i = 0; i < n; i++) {
 143                 x = samples[i].time;
 144                 y = samples[i].offset;
 145                 r = fabs(x * *slope + *intercept - y);
 146                 if (*r_max < r)
 147                         *r_max = r;
 148                 r2_sum += r * r;
 149         }
 150
 151         *r_stddev = sqrt(r2_sum / n);
 152 }
 153
 154 static int run_test(int calibration, double freq_base, double freq_step)
 155 {
 156         struct sample samples[SAMPLES];
 157         double intercept, slope, stddev1, max1, stddev2, max2;
 158         double freq_error1, freq_error2;
 159         int i;
 160
 161         set_frequency(freq_base);
 162
 163         for (i = 0; i < 10; i++)
 164                 usleep(1e6 * MEAN_SAMPLE_INTERVAL / 10);
 165
 166         reset_ntp_error();
 167
 168         set_frequency(freq_base + freq_step);
 169
 170         for (i = 0; i < 10; i++)
 171                 usleep(rand() % 2000000 * STEP_INTERVAL / 10);
 172
 173         set_frequency(freq_base);
 174
 175         for (i = 0; i < SAMPLES; i++) {
 176                 usleep(rand() % 2000000 * MEAN_SAMPLE_INTERVAL);
 177                 get_sample(&samples[i]);
 178         }
 179
 180         if (calibration) {
 181                 regress(samples, SAMPLES, &intercept, &slope, &stddev1, &max1);
 182                 mono_freq_offset = slope;
 183                 printf("CLOCK_MONOTONIC_RAW frequency offset: %11.3f ppm\n",
 184                        1e6 * mono_freq_offset);
 185                 return 0;
 186         }
 187
 188         regress(samples, SAMPLES / 2, &intercept, &slope, &stddev1, &max1);
 189         freq_error1 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
 190                         freq_base;
 191
 192         regress(samples + SAMPLES / 2, SAMPLES / 2, &intercept, &slope,
 193                 &stddev2, &max2);
 194         freq_error2 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
 195                         freq_base;
 196
 197         printf("%6.0f %+10.3f %6.0f %7.0f %+10.3f %6.0f %7.0f\t",
 198                1e6 * freq_step,
 199                1e6 * freq_error1, 1e9 * stddev1, 1e9 * max1,
 200                1e6 * freq_error2, 1e9 * stddev2, 1e9 * max2);
 201
 202         if (fabs(freq_error2) > MAX_FREQ_ERROR || stddev2 > MAX_STDDEV) {
 203                 printf("[FAIL]\n");
 204                 return 1;
 205         }
 206
 207         printf("[OK]\n");
 208         return 0;
 209 }
 210
 211 static void init_test(void)
 212 {
 213         struct timespec ts;
 214         struct sample sample;
 215
 216         if (clock_gettime(CLOCK_MONOTONIC_RAW, &ts)) {
 217                 perror("[FAIL] clock_gettime(CLOCK_MONOTONIC_RAW)");
 218                 ksft_exit_fail();
 219         }
 220
 221         mono_raw_base = ts.tv_sec;
 222
 223         if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
 224                 perror("[FAIL] clock_gettime(CLOCK_MONOTONIC)");
 225                 ksft_exit_fail();
 226         }
 227
 228         mono_base = ts.tv_sec;
 229
 230         user_hz = sysconf(_SC_CLK_TCK);
 231
 232         precision = get_sample(&sample) / 2.0;
 233         printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t",
 234                1e9 * precision);
 235
 236         if (precision > MAX_PRECISION)
 237                 ksft_exit_skip("precision: %.0f ns > MAX_PRECISION: %.0f ns\n",
 238                                 1e9 * precision, 1e9 * MAX_PRECISION);
 239
 240         printf("[OK]\n");
 241         srand(ts.tv_sec ^ ts.tv_nsec);
 242
 243         run_test(1, 0.0, 0.0);
 244 }
 245
 246 int main(int argc, char **argv)
 247 {
 248         double freq_base, freq_step;
 249         int i, j, fails = 0;
 250
 251         init_test();
 252
 253         printf("Checking response to frequency step:\n");
 254         printf("  Step           1st interval              2nd interval\n");
 255         printf("             Freq    Dev     Max       Freq    Dev     Max\n");
 256
 257         for (i = 2; i >= 0; i--) {
 258                 for (j = 0; j < 5; j++) {
 259                         freq_base = (rand() % (1 << 24) - (1 << 23)) / 65536e6;
 260                         freq_step = 10e-6 * (1 << (6 * i));
 261                         fails += run_test(0, freq_base, freq_step);
 262                 }
 263         }
 264
 265         set_frequency(0.0);
 266
 267         if (fails)
 268                 return ksft_exit_fail();
 269
 270         return ksft_exit_pass();
 271 }