// SPDX-License-Identifier: GPL-2.0-only
/*
* 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 <[email protected]> 2017
*/
#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 500e-9
#define MAX_FREQ_ERROR 0.02e-6
#define MAX_STDDEV 50e-9
#ifndef ADJ_SETOFFSET
#define ADJ_SETOFFSET 0x0100
#endif
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)
ksft_exit_skip("precision: %.0f ns > MAX_PRECISION: %.0f ns\n",
1e9 * precision, 1e9 * MAX_PRECISION);
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();
}
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