aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/tools/testing/selftests/timers/freq-step.c
blob: 22312eb4c9419a5fc3ee7054b4a0b604f7cdafce (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
/*
 * 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)
		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();
}