1 /*
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.
7  *
8  * Copyright (C) Miroslav Lichvar <mlichvar@redhat.com>  2017
9  *
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.
13  *
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.
18  */
19 
20 #include <math.h>
21 #include <stdio.h>
22 #include <sys/timex.h>
23 #include <time.h>
24 #include <unistd.h>
25 
26 #include "../kselftest.h"
27 
28 #define SAMPLES 100
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
35 
36 #ifndef ADJ_SETOFFSET
37   #define ADJ_SETOFFSET 0x0100
38 #endif
39 
40 struct sample {
41 	double offset;
42 	double time;
43 };
44 
45 static time_t mono_raw_base;
46 static time_t mono_base;
47 static long user_hz;
48 static double precision;
49 static double mono_freq_offset;
50 
51 static double diff_timespec(struct timespec *ts1, struct timespec *ts2)
52 {
53 	return ts1->tv_sec - ts2->tv_sec + (ts1->tv_nsec - ts2->tv_nsec) / 1e9;
54 }
55 
56 static double get_sample(struct sample *sample)
57 {
58 	double delay, mindelay = 0.0;
59 	struct timespec ts1, ts2, ts3;
60 	int i;
61 
62 	for (i = 0; i < SAMPLE_READINGS; i++) {
63 		clock_gettime(CLOCK_MONOTONIC_RAW, &ts1);
64 		clock_gettime(CLOCK_MONOTONIC, &ts2);
65 		clock_gettime(CLOCK_MONOTONIC_RAW, &ts3);
66 
67 		ts1.tv_sec -= mono_raw_base;
68 		ts2.tv_sec -= mono_base;
69 		ts3.tv_sec -= mono_raw_base;
70 
71 		delay = diff_timespec(&ts3, &ts1);
72 		if (delay <= 1e-9) {
73 			i--;
74 			continue;
75 		}
76 
77 		if (!i || delay < mindelay) {
78 			sample->offset = diff_timespec(&ts2, &ts1);
79 			sample->offset -= delay / 2.0;
80 			sample->time = ts1.tv_sec + ts1.tv_nsec / 1e9;
81 			mindelay = delay;
82 		}
83 	}
84 
85 	return mindelay;
86 }
87 
88 static void reset_ntp_error(void)
89 {
90 	struct timex txc;
91 
92 	txc.modes = ADJ_SETOFFSET;
93 	txc.time.tv_sec = 0;
94 	txc.time.tv_usec = 0;
95 
96 	if (adjtimex(&txc) < 0) {
97 		perror("[FAIL] adjtimex");
98 		ksft_exit_fail();
99 	}
100 }
101 
102 static void set_frequency(double freq)
103 {
104 	struct timex txc;
105 	int tick_offset;
106 
107 	tick_offset = 1e6 * freq / user_hz;
108 
109 	txc.modes = ADJ_TICK | ADJ_FREQUENCY;
110 	txc.tick = 1000000 / user_hz + tick_offset;
111 	txc.freq = (1e6 * freq - user_hz * tick_offset) * (1 << 16);
112 
113 	if (adjtimex(&txc) < 0) {
114 		perror("[FAIL] adjtimex");
115 		ksft_exit_fail();
116 	}
117 }
118 
119 static void regress(struct sample *samples, int n, double *intercept,
120 		    double *slope, double *r_stddev, double *r_max)
121 {
122 	double x, y, r, x_sum, y_sum, xy_sum, x2_sum, r2_sum;
123 	int i;
124 
125 	x_sum = 0.0, y_sum = 0.0, xy_sum = 0.0, x2_sum = 0.0;
126 
127 	for (i = 0; i < n; i++) {
128 		x = samples[i].time;
129 		y = samples[i].offset;
130 
131 		x_sum += x;
132 		y_sum += y;
133 		xy_sum += x * y;
134 		x2_sum += x * x;
135 	}
136 
137 	*slope = (xy_sum - x_sum * y_sum / n) / (x2_sum - x_sum * x_sum / n);
138 	*intercept = (y_sum - *slope * x_sum) / n;
139 
140 	*r_max = 0.0, r2_sum = 0.0;
141 
142 	for (i = 0; i < n; i++) {
143 		x = samples[i].time;
144 		y = samples[i].offset;
145 		r = fabs(x * *slope + *intercept - y);
146 		if (*r_max < r)
147 			*r_max = r;
148 		r2_sum += r * r;
149 	}
150 
151 	*r_stddev = sqrt(r2_sum / n);
152 }
153 
154 static int run_test(int calibration, double freq_base, double freq_step)
155 {
156 	struct sample samples[SAMPLES];
157 	double intercept, slope, stddev1, max1, stddev2, max2;
158 	double freq_error1, freq_error2;
159 	int i;
160 
161 	set_frequency(freq_base);
162 
163 	for (i = 0; i < 10; i++)
164 		usleep(1e6 * MEAN_SAMPLE_INTERVAL / 10);
165 
166 	reset_ntp_error();
167 
168 	set_frequency(freq_base + freq_step);
169 
170 	for (i = 0; i < 10; i++)
171 		usleep(rand() % 2000000 * STEP_INTERVAL / 10);
172 
173 	set_frequency(freq_base);
174 
175 	for (i = 0; i < SAMPLES; i++) {
176 		usleep(rand() % 2000000 * MEAN_SAMPLE_INTERVAL);
177 		get_sample(&samples[i]);
178 	}
179 
180 	if (calibration) {
181 		regress(samples, SAMPLES, &intercept, &slope, &stddev1, &max1);
182 		mono_freq_offset = slope;
183 		printf("CLOCK_MONOTONIC_RAW frequency offset: %11.3f ppm\n",
184 		       1e6 * mono_freq_offset);
185 		return 0;
186 	}
187 
188 	regress(samples, SAMPLES / 2, &intercept, &slope, &stddev1, &max1);
189 	freq_error1 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
190 			freq_base;
191 
192 	regress(samples + SAMPLES / 2, SAMPLES / 2, &intercept, &slope,
193 		&stddev2, &max2);
194 	freq_error2 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
195 			freq_base;
196 
197 	printf("%6.0f %+10.3f %6.0f %7.0f %+10.3f %6.0f %7.0f\t",
198 	       1e6 * freq_step,
199 	       1e6 * freq_error1, 1e9 * stddev1, 1e9 * max1,
200 	       1e6 * freq_error2, 1e9 * stddev2, 1e9 * max2);
201 
202 	if (fabs(freq_error2) > MAX_FREQ_ERROR || stddev2 > MAX_STDDEV) {
203 		printf("[FAIL]\n");
204 		return 1;
205 	}
206 
207 	printf("[OK]\n");
208 	return 0;
209 }
210 
211 static void init_test(void)
212 {
213 	struct timespec ts;
214 	struct sample sample;
215 
216 	if (clock_gettime(CLOCK_MONOTONIC_RAW, &ts)) {
217 		perror("[FAIL] clock_gettime(CLOCK_MONOTONIC_RAW)");
218 		ksft_exit_fail();
219 	}
220 
221 	mono_raw_base = ts.tv_sec;
222 
223 	if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
224 		perror("[FAIL] clock_gettime(CLOCK_MONOTONIC)");
225 		ksft_exit_fail();
226 	}
227 
228 	mono_base = ts.tv_sec;
229 
230 	user_hz = sysconf(_SC_CLK_TCK);
231 
232 	precision = get_sample(&sample) / 2.0;
233 	printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t",
234 	       1e9 * precision);
235 
236 	if (precision > MAX_PRECISION)
237 		ksft_exit_skip("precision: %.0f ns > MAX_PRECISION: %.0f ns\n",
238 				1e9 * precision, 1e9 * MAX_PRECISION);
239 
240 	printf("[OK]\n");
241 	srand(ts.tv_sec ^ ts.tv_nsec);
242 
243 	run_test(1, 0.0, 0.0);
244 }
245 
246 int main(int argc, char **argv)
247 {
248 	double freq_base, freq_step;
249 	int i, j, fails = 0;
250 
251 	init_test();
252 
253 	printf("Checking response to frequency step:\n");
254 	printf("  Step           1st interval              2nd interval\n");
255 	printf("             Freq    Dev     Max       Freq    Dev     Max\n");
256 
257 	for (i = 2; i >= 0; i--) {
258 		for (j = 0; j < 5; j++) {
259 			freq_base = (rand() % (1 << 24) - (1 << 23)) / 65536e6;
260 			freq_step = 10e-6 * (1 << (6 * i));
261 			fails += run_test(0, freq_base, freq_step);
262 		}
263 	}
264 
265 	set_frequency(0.0);
266 
267 	if (fails)
268 		return ksft_exit_fail();
269 
270 	return ksft_exit_pass();
271 }
272