diff options
Diffstat (limited to 'tools/testing/selftests/timers/freq-step.c')
| -rw-r--r-- | tools/testing/selftests/timers/freq-step.c | 268 |
1 files changed, 268 insertions, 0 deletions
diff --git a/tools/testing/selftests/timers/freq-step.c b/tools/testing/selftests/timers/freq-step.c new file mode 100644 index 0000000..e8c6183 --- /dev/null +++ b/tools/testing/selftests/timers/freq-step.c @@ -0,0 +1,268 @@ +/* + * This test checks the response of the system clock to frequency + * steps made with adjtimex(). The frequency error and stability of + * the CLOCK_MONOTONIC clock relative to the CLOCK_MONOTONIC_RAW clock + * is measured in two intervals following the step. The test fails if + * values from the second interval exceed specified limits. + * + * Copyright (C) Miroslav Lichvar <mlichvar@redhat.com> 2017 + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of version 2 of the GNU General Public License as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + */ + +#include <math.h> +#include <stdio.h> +#include <sys/timex.h> +#include <time.h> +#include <unistd.h> + +#include "../kselftest.h" + +#define SAMPLES 100 +#define SAMPLE_READINGS 10 +#define MEAN_SAMPLE_INTERVAL 0.1 +#define STEP_INTERVAL 1.0 +#define MAX_PRECISION 100e-9 +#define MAX_FREQ_ERROR 10e-6 +#define MAX_STDDEV 1000e-9 + +struct sample { + double offset; + double time; +}; + +static time_t mono_raw_base; +static time_t mono_base; +static long user_hz; +static double precision; +static double mono_freq_offset; + +static double diff_timespec(struct timespec *ts1, struct timespec *ts2) +{ + return ts1->tv_sec - ts2->tv_sec + (ts1->tv_nsec - ts2->tv_nsec) / 1e9; +} + +static double get_sample(struct sample *sample) +{ + double delay, mindelay = 0.0; + struct timespec ts1, ts2, ts3; + int i; + + for (i = 0; i < SAMPLE_READINGS; i++) { + clock_gettime(CLOCK_MONOTONIC_RAW, &ts1); + clock_gettime(CLOCK_MONOTONIC, &ts2); + clock_gettime(CLOCK_MONOTONIC_RAW, &ts3); + + ts1.tv_sec -= mono_raw_base; + ts2.tv_sec -= mono_base; + ts3.tv_sec -= mono_raw_base; + + delay = diff_timespec(&ts3, &ts1); + if (delay <= 1e-9) { + i--; + continue; + } + + if (!i || delay < mindelay) { + sample->offset = diff_timespec(&ts2, &ts1); + sample->offset -= delay / 2.0; + sample->time = ts1.tv_sec + ts1.tv_nsec / 1e9; + mindelay = delay; + } + } + + return mindelay; +} + +static void reset_ntp_error(void) +{ + struct timex txc; + + txc.modes = ADJ_SETOFFSET; + txc.time.tv_sec = 0; + txc.time.tv_usec = 0; + + if (adjtimex(&txc) < 0) { + perror("[FAIL] adjtimex"); + ksft_exit_fail(); + } +} + +static void set_frequency(double freq) +{ + struct timex txc; + int tick_offset; + + tick_offset = 1e6 * freq / user_hz; + + txc.modes = ADJ_TICK | ADJ_FREQUENCY; + txc.tick = 1000000 / user_hz + tick_offset; + txc.freq = (1e6 * freq - user_hz * tick_offset) * (1 << 16); + + if (adjtimex(&txc) < 0) { + perror("[FAIL] adjtimex"); + ksft_exit_fail(); + } +} + +static void regress(struct sample *samples, int n, double *intercept, + double *slope, double *r_stddev, double *r_max) +{ + double x, y, r, x_sum, y_sum, xy_sum, x2_sum, r2_sum; + int i; + + x_sum = 0.0, y_sum = 0.0, xy_sum = 0.0, x2_sum = 0.0; + + for (i = 0; i < n; i++) { + x = samples[i].time; + y = samples[i].offset; + + x_sum += x; + y_sum += y; + xy_sum += x * y; + x2_sum += x * x; + } + + *slope = (xy_sum - x_sum * y_sum / n) / (x2_sum - x_sum * x_sum / n); + *intercept = (y_sum - *slope * x_sum) / n; + + *r_max = 0.0, r2_sum = 0.0; + + for (i = 0; i < n; i++) { + x = samples[i].time; + y = samples[i].offset; + r = fabs(x * *slope + *intercept - y); + if (*r_max < r) + *r_max = r; + r2_sum += r * r; + } + + *r_stddev = sqrt(r2_sum / n); +} + +static int run_test(int calibration, double freq_base, double freq_step) +{ + struct sample samples[SAMPLES]; + double intercept, slope, stddev1, max1, stddev2, max2; + double freq_error1, freq_error2; + int i; + + set_frequency(freq_base); + + for (i = 0; i < 10; i++) + usleep(1e6 * MEAN_SAMPLE_INTERVAL / 10); + + reset_ntp_error(); + + set_frequency(freq_base + freq_step); + + for (i = 0; i < 10; i++) + usleep(rand() % 2000000 * STEP_INTERVAL / 10); + + set_frequency(freq_base); + + for (i = 0; i < SAMPLES; i++) { + usleep(rand() % 2000000 * MEAN_SAMPLE_INTERVAL); + get_sample(&samples[i]); + } + + if (calibration) { + regress(samples, SAMPLES, &intercept, &slope, &stddev1, &max1); + mono_freq_offset = slope; + printf("CLOCK_MONOTONIC_RAW frequency offset: %11.3f ppm\n", + 1e6 * mono_freq_offset); + return 0; + } + + regress(samples, SAMPLES / 2, &intercept, &slope, &stddev1, &max1); + freq_error1 = slope * (1.0 - mono_freq_offset) - mono_freq_offset - + freq_base; + + regress(samples + SAMPLES / 2, SAMPLES / 2, &intercept, &slope, + &stddev2, &max2); + freq_error2 = slope * (1.0 - mono_freq_offset) - mono_freq_offset - + freq_base; + + printf("%6.0f %+10.3f %6.0f %7.0f %+10.3f %6.0f %7.0f\t", + 1e6 * freq_step, + 1e6 * freq_error1, 1e9 * stddev1, 1e9 * max1, + 1e6 * freq_error2, 1e9 * stddev2, 1e9 * max2); + + if (fabs(freq_error2) > MAX_FREQ_ERROR || stddev2 > MAX_STDDEV) { + printf("[FAIL]\n"); + return 1; + } + + printf("[OK]\n"); + return 0; +} + +static void init_test(void) +{ + struct timespec ts; + struct sample sample; + + if (clock_gettime(CLOCK_MONOTONIC_RAW, &ts)) { + perror("[FAIL] clock_gettime(CLOCK_MONOTONIC_RAW)"); + ksft_exit_fail(); + } + + mono_raw_base = ts.tv_sec; + + if (clock_gettime(CLOCK_MONOTONIC, &ts)) { + perror("[FAIL] clock_gettime(CLOCK_MONOTONIC)"); + ksft_exit_fail(); + } + + mono_base = ts.tv_sec; + + user_hz = sysconf(_SC_CLK_TCK); + + precision = get_sample(&sample) / 2.0; + printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t", + 1e9 * precision); + + if (precision > MAX_PRECISION) { + printf("[SKIP]\n"); + ksft_exit_skip(); + } + + printf("[OK]\n"); + srand(ts.tv_sec ^ ts.tv_nsec); + + run_test(1, 0.0, 0.0); +} + +int main(int argc, char **argv) +{ + double freq_base, freq_step; + int i, j, fails = 0; + + init_test(); + + printf("Checking response to frequency step:\n"); + printf(" Step 1st interval 2nd interval\n"); + printf(" Freq Dev Max Freq Dev Max\n"); + + for (i = 2; i >= 0; i--) { + for (j = 0; j < 5; j++) { + freq_base = (rand() % (1 << 24) - (1 << 23)) / 65536e6; + freq_step = 10e-6 * (1 << (6 * i)); + fails += run_test(0, freq_base, freq_step); + } + } + + set_frequency(0.0); + + if (fails) + ksft_exit_fail(); + + ksft_exit_pass(); +} |
