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.
8 * Copyright (C) Miroslav Lichvar <mlichvar@redhat.com> 2017
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.
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.
22 #include <sys/timex.h>
26 #include "../kselftest.h"
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
41 static time_t mono_raw_base;
42 static time_t mono_base;
44 static double precision;
45 static double mono_freq_offset;
47 static double diff_timespec(struct timespec *ts1, struct timespec *ts2)
49 return ts1->tv_sec - ts2->tv_sec + (ts1->tv_nsec - ts2->tv_nsec) / 1e9;
52 static double get_sample(struct sample *sample)
54 double delay, mindelay = 0.0;
55 struct timespec ts1, ts2, ts3;
58 for (i = 0; i < SAMPLE_READINGS; i++) {
59 clock_gettime(CLOCK_MONOTONIC_RAW, &ts1);
60 clock_gettime(CLOCK_MONOTONIC, &ts2);
61 clock_gettime(CLOCK_MONOTONIC_RAW, &ts3);
63 ts1.tv_sec -= mono_raw_base;
64 ts2.tv_sec -= mono_base;
65 ts3.tv_sec -= mono_raw_base;
67 delay = diff_timespec(&ts3, &ts1);
73 if (!i || delay < mindelay) {
74 sample->offset = diff_timespec(&ts2, &ts1);
75 sample->offset -= delay / 2.0;
76 sample->time = ts1.tv_sec + ts1.tv_nsec / 1e9;
84 static void reset_ntp_error(void)
88 txc.modes = ADJ_SETOFFSET;
92 if (adjtimex(&txc) < 0) {
93 perror("[FAIL] adjtimex");
98 static void set_frequency(double freq)
103 tick_offset = 1e6 * freq / user_hz;
105 txc.modes = ADJ_TICK | ADJ_FREQUENCY;
106 txc.tick = 1000000 / user_hz + tick_offset;
107 txc.freq = (1e6 * freq - user_hz * tick_offset) * (1 << 16);
109 if (adjtimex(&txc) < 0) {
110 perror("[FAIL] adjtimex");
115 static void regress(struct sample *samples, int n, double *intercept,
116 double *slope, double *r_stddev, double *r_max)
118 double x, y, r, x_sum, y_sum, xy_sum, x2_sum, r2_sum;
121 x_sum = 0.0, y_sum = 0.0, xy_sum = 0.0, x2_sum = 0.0;
123 for (i = 0; i < n; i++) {
125 y = samples[i].offset;
133 *slope = (xy_sum - x_sum * y_sum / n) / (x2_sum - x_sum * x_sum / n);
134 *intercept = (y_sum - *slope * x_sum) / n;
136 *r_max = 0.0, r2_sum = 0.0;
138 for (i = 0; i < n; i++) {
140 y = samples[i].offset;
141 r = fabs(x * *slope + *intercept - y);
147 *r_stddev = sqrt(r2_sum / n);
150 static int run_test(int calibration, double freq_base, double freq_step)
152 struct sample samples[SAMPLES];
153 double intercept, slope, stddev1, max1, stddev2, max2;
154 double freq_error1, freq_error2;
157 set_frequency(freq_base);
159 for (i = 0; i < 10; i++)
160 usleep(1e6 * MEAN_SAMPLE_INTERVAL / 10);
164 set_frequency(freq_base + freq_step);
166 for (i = 0; i < 10; i++)
167 usleep(rand() % 2000000 * STEP_INTERVAL / 10);
169 set_frequency(freq_base);
171 for (i = 0; i < SAMPLES; i++) {
172 usleep(rand() % 2000000 * MEAN_SAMPLE_INTERVAL);
173 get_sample(&samples[i]);
177 regress(samples, SAMPLES, &intercept, &slope, &stddev1, &max1);
178 mono_freq_offset = slope;
179 printf("CLOCK_MONOTONIC_RAW frequency offset: %11.3f ppm\n",
180 1e6 * mono_freq_offset);
184 regress(samples, SAMPLES / 2, &intercept, &slope, &stddev1, &max1);
185 freq_error1 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
188 regress(samples + SAMPLES / 2, SAMPLES / 2, &intercept, &slope,
190 freq_error2 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
193 printf("%6.0f %+10.3f %6.0f %7.0f %+10.3f %6.0f %7.0f\t",
195 1e6 * freq_error1, 1e9 * stddev1, 1e9 * max1,
196 1e6 * freq_error2, 1e9 * stddev2, 1e9 * max2);
198 if (fabs(freq_error2) > MAX_FREQ_ERROR || stddev2 > MAX_STDDEV) {
207 static void init_test(void)
210 struct sample sample;
212 if (clock_gettime(CLOCK_MONOTONIC_RAW, &ts)) {
213 perror("[FAIL] clock_gettime(CLOCK_MONOTONIC_RAW)");
217 mono_raw_base = ts.tv_sec;
219 if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
220 perror("[FAIL] clock_gettime(CLOCK_MONOTONIC)");
224 mono_base = ts.tv_sec;
226 user_hz = sysconf(_SC_CLK_TCK);
228 precision = get_sample(&sample) / 2.0;
229 printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t",
232 if (precision > MAX_PRECISION)
233 ksft_exit_skip("precision: %.0f ns > MAX_PRECISION: %.0f ns\n",
234 1e9 * precision, 1e9 * MAX_PRECISION);
237 srand(ts.tv_sec ^ ts.tv_nsec);
239 run_test(1, 0.0, 0.0);
242 int main(int argc, char **argv)
244 double freq_base, freq_step;
249 printf("Checking response to frequency step:\n");
250 printf(" Step 1st interval 2nd interval\n");
251 printf(" Freq Dev Max Freq Dev Max\n");
253 for (i = 2; i >= 0; i--) {
254 for (j = 0; j < 5; j++) {
255 freq_base = (rand() % (1 << 24) - (1 << 23)) / 65536e6;
256 freq_step = 10e-6 * (1 << (6 * i));
257 fails += run_test(0, freq_base, freq_step);