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d21e43f2ef
PTI has a significant impact on precision of the MONOTONIC_RAW clock,
which prevents a lot of computers from running the freq-step test.
Increase the maximum acceptable precision for the test to not be skipped
to 500 nanoseconds.
After commit 78b98e3c5a
("timekeeping/ntp: Determine the multiplier
directly from NTP tick length") the frequency and time errors should be
much smaller. Reduce the maximum acceptable values for the test to pass
to 0.02 ppm and 50 nanoseconds respectively.
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
Link: https://lkml.kernel.org/r/20190618160612.21957-1-mlichvar@redhat.com
264 lines
5.8 KiB
C
264 lines
5.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* This test checks the response of the system clock to frequency
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* steps made with adjtimex(). The frequency error and stability of
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* the CLOCK_MONOTONIC clock relative to the CLOCK_MONOTONIC_RAW clock
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* is measured in two intervals following the step. The test fails if
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* values from the second interval exceed specified limits.
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*
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* Copyright (C) Miroslav Lichvar <mlichvar@redhat.com> 2017
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*/
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#include <math.h>
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#include <stdio.h>
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#include <sys/timex.h>
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#include <time.h>
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#include <unistd.h>
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#include "../kselftest.h"
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#define SAMPLES 100
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#define SAMPLE_READINGS 10
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#define MEAN_SAMPLE_INTERVAL 0.1
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#define STEP_INTERVAL 1.0
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#define MAX_PRECISION 500e-9
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#define MAX_FREQ_ERROR 0.02e-6
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#define MAX_STDDEV 50e-9
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#ifndef ADJ_SETOFFSET
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#define ADJ_SETOFFSET 0x0100
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#endif
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struct sample {
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double offset;
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double time;
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};
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static time_t mono_raw_base;
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static time_t mono_base;
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static long user_hz;
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static double precision;
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static double mono_freq_offset;
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static double diff_timespec(struct timespec *ts1, struct timespec *ts2)
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{
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return ts1->tv_sec - ts2->tv_sec + (ts1->tv_nsec - ts2->tv_nsec) / 1e9;
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}
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static double get_sample(struct sample *sample)
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{
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double delay, mindelay = 0.0;
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struct timespec ts1, ts2, ts3;
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int i;
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for (i = 0; i < SAMPLE_READINGS; i++) {
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clock_gettime(CLOCK_MONOTONIC_RAW, &ts1);
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clock_gettime(CLOCK_MONOTONIC, &ts2);
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clock_gettime(CLOCK_MONOTONIC_RAW, &ts3);
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ts1.tv_sec -= mono_raw_base;
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ts2.tv_sec -= mono_base;
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ts3.tv_sec -= mono_raw_base;
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delay = diff_timespec(&ts3, &ts1);
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if (delay <= 1e-9) {
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i--;
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continue;
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}
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if (!i || delay < mindelay) {
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sample->offset = diff_timespec(&ts2, &ts1);
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sample->offset -= delay / 2.0;
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sample->time = ts1.tv_sec + ts1.tv_nsec / 1e9;
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mindelay = delay;
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}
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}
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return mindelay;
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}
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static void reset_ntp_error(void)
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{
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struct timex txc;
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txc.modes = ADJ_SETOFFSET;
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txc.time.tv_sec = 0;
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txc.time.tv_usec = 0;
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if (adjtimex(&txc) < 0) {
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perror("[FAIL] adjtimex");
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ksft_exit_fail();
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}
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}
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static void set_frequency(double freq)
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{
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struct timex txc;
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int tick_offset;
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tick_offset = 1e6 * freq / user_hz;
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txc.modes = ADJ_TICK | ADJ_FREQUENCY;
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txc.tick = 1000000 / user_hz + tick_offset;
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txc.freq = (1e6 * freq - user_hz * tick_offset) * (1 << 16);
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if (adjtimex(&txc) < 0) {
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perror("[FAIL] adjtimex");
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ksft_exit_fail();
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}
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}
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static void regress(struct sample *samples, int n, double *intercept,
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double *slope, double *r_stddev, double *r_max)
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{
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double x, y, r, x_sum, y_sum, xy_sum, x2_sum, r2_sum;
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int i;
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x_sum = 0.0, y_sum = 0.0, xy_sum = 0.0, x2_sum = 0.0;
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for (i = 0; i < n; i++) {
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x = samples[i].time;
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y = samples[i].offset;
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x_sum += x;
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y_sum += y;
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xy_sum += x * y;
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x2_sum += x * x;
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}
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*slope = (xy_sum - x_sum * y_sum / n) / (x2_sum - x_sum * x_sum / n);
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*intercept = (y_sum - *slope * x_sum) / n;
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*r_max = 0.0, r2_sum = 0.0;
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for (i = 0; i < n; i++) {
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x = samples[i].time;
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y = samples[i].offset;
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r = fabs(x * *slope + *intercept - y);
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if (*r_max < r)
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*r_max = r;
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r2_sum += r * r;
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}
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*r_stddev = sqrt(r2_sum / n);
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}
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static int run_test(int calibration, double freq_base, double freq_step)
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{
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struct sample samples[SAMPLES];
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double intercept, slope, stddev1, max1, stddev2, max2;
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double freq_error1, freq_error2;
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int i;
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set_frequency(freq_base);
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for (i = 0; i < 10; i++)
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usleep(1e6 * MEAN_SAMPLE_INTERVAL / 10);
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reset_ntp_error();
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set_frequency(freq_base + freq_step);
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for (i = 0; i < 10; i++)
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usleep(rand() % 2000000 * STEP_INTERVAL / 10);
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set_frequency(freq_base);
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for (i = 0; i < SAMPLES; i++) {
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usleep(rand() % 2000000 * MEAN_SAMPLE_INTERVAL);
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get_sample(&samples[i]);
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}
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if (calibration) {
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regress(samples, SAMPLES, &intercept, &slope, &stddev1, &max1);
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mono_freq_offset = slope;
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printf("CLOCK_MONOTONIC_RAW frequency offset: %11.3f ppm\n",
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1e6 * mono_freq_offset);
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return 0;
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}
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regress(samples, SAMPLES / 2, &intercept, &slope, &stddev1, &max1);
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freq_error1 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
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freq_base;
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regress(samples + SAMPLES / 2, SAMPLES / 2, &intercept, &slope,
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&stddev2, &max2);
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freq_error2 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
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freq_base;
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printf("%6.0f %+10.3f %6.0f %7.0f %+10.3f %6.0f %7.0f\t",
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1e6 * freq_step,
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1e6 * freq_error1, 1e9 * stddev1, 1e9 * max1,
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1e6 * freq_error2, 1e9 * stddev2, 1e9 * max2);
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if (fabs(freq_error2) > MAX_FREQ_ERROR || stddev2 > MAX_STDDEV) {
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printf("[FAIL]\n");
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return 1;
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}
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printf("[OK]\n");
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return 0;
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}
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static void init_test(void)
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{
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struct timespec ts;
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struct sample sample;
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if (clock_gettime(CLOCK_MONOTONIC_RAW, &ts)) {
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perror("[FAIL] clock_gettime(CLOCK_MONOTONIC_RAW)");
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ksft_exit_fail();
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}
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mono_raw_base = ts.tv_sec;
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if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
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perror("[FAIL] clock_gettime(CLOCK_MONOTONIC)");
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ksft_exit_fail();
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}
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mono_base = ts.tv_sec;
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user_hz = sysconf(_SC_CLK_TCK);
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precision = get_sample(&sample) / 2.0;
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printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t",
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1e9 * precision);
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if (precision > MAX_PRECISION)
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ksft_exit_skip("precision: %.0f ns > MAX_PRECISION: %.0f ns\n",
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1e9 * precision, 1e9 * MAX_PRECISION);
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printf("[OK]\n");
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srand(ts.tv_sec ^ ts.tv_nsec);
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run_test(1, 0.0, 0.0);
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}
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int main(int argc, char **argv)
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{
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double freq_base, freq_step;
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int i, j, fails = 0;
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init_test();
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printf("Checking response to frequency step:\n");
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printf(" Step 1st interval 2nd interval\n");
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printf(" Freq Dev Max Freq Dev Max\n");
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for (i = 2; i >= 0; i--) {
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for (j = 0; j < 5; j++) {
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freq_base = (rand() % (1 << 24) - (1 << 23)) / 65536e6;
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freq_step = 10e-6 * (1 << (6 * i));
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fails += run_test(0, freq_base, freq_step);
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}
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}
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set_frequency(0.0);
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if (fails)
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return ksft_exit_fail();
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return ksft_exit_pass();
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}
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