1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * This test checks the response of the system clock to frequency
4  * steps made with adjtimex(). The frequency error and stability of
5  * the CLOCK_MONOTONIC clock relative to the CLOCK_MONOTONIC_RAW clock
6  * is measured in two intervals following the step. The test fails if
7  * values from the second interval exceed specified limits.
8  *
9  * Copyright (C) Miroslav Lichvar <mlichvar@redhat.com>  2017
10  */
11 
12 #include <math.h>
13 #include <stdio.h>
14 #include <sys/timex.h>
15 #include <time.h>
16 #include <unistd.h>
17 
18 #include "../kselftest.h"
19 
20 #define SAMPLES 100
21 #define SAMPLE_READINGS 10
22 #define MEAN_SAMPLE_INTERVAL 0.1
23 #define STEP_INTERVAL 1.0
24 #define MAX_PRECISION 500e-9
25 #define MAX_FREQ_ERROR 0.02e-6
26 #define MAX_STDDEV 50e-9
27 
28 #ifndef ADJ_SETOFFSET
29   #define ADJ_SETOFFSET 0x0100
30 #endif
31 
32 struct sample {
33 	double offset;
34 	double time;
35 };
36 
37 static time_t mono_raw_base;
38 static time_t mono_base;
39 static long user_hz;
40 static double precision;
41 static double mono_freq_offset;
42 
43 static double diff_timespec(struct timespec *ts1, struct timespec *ts2)
44 {
45 	return ts1->tv_sec - ts2->tv_sec + (ts1->tv_nsec - ts2->tv_nsec) / 1e9;
46 }
47 
48 static double get_sample(struct sample *sample)
49 {
50 	double delay, mindelay = 0.0;
51 	struct timespec ts1, ts2, ts3;
52 	int i;
53 
54 	for (i = 0; i < SAMPLE_READINGS; i++) {
55 		clock_gettime(CLOCK_MONOTONIC_RAW, &ts1);
56 		clock_gettime(CLOCK_MONOTONIC, &ts2);
57 		clock_gettime(CLOCK_MONOTONIC_RAW, &ts3);
58 
59 		ts1.tv_sec -= mono_raw_base;
60 		ts2.tv_sec -= mono_base;
61 		ts3.tv_sec -= mono_raw_base;
62 
63 		delay = diff_timespec(&ts3, &ts1);
64 		if (delay <= 1e-9) {
65 			i--;
66 			continue;
67 		}
68 
69 		if (!i || delay < mindelay) {
70 			sample->offset = diff_timespec(&ts2, &ts1);
71 			sample->offset -= delay / 2.0;
72 			sample->time = ts1.tv_sec + ts1.tv_nsec / 1e9;
73 			mindelay = delay;
74 		}
75 	}
76 
77 	return mindelay;
78 }
79 
80 static void reset_ntp_error(void)
81 {
82 	struct timex txc;
83 
84 	txc.modes = ADJ_SETOFFSET;
85 	txc.time.tv_sec = 0;
86 	txc.time.tv_usec = 0;
87 
88 	if (adjtimex(&txc) < 0) {
89 		perror("[FAIL] adjtimex");
90 		ksft_exit_fail();
91 	}
92 }
93 
94 static void set_frequency(double freq)
95 {
96 	struct timex txc;
97 	int tick_offset;
98 
99 	tick_offset = 1e6 * freq / user_hz;
100 
101 	txc.modes = ADJ_TICK | ADJ_FREQUENCY;
102 	txc.tick = 1000000 / user_hz + tick_offset;
103 	txc.freq = (1e6 * freq - user_hz * tick_offset) * (1 << 16);
104 
105 	if (adjtimex(&txc) < 0) {
106 		perror("[FAIL] adjtimex");
107 		ksft_exit_fail();
108 	}
109 }
110 
111 static void regress(struct sample *samples, int n, double *intercept,
112 		    double *slope, double *r_stddev, double *r_max)
113 {
114 	double x, y, r, x_sum, y_sum, xy_sum, x2_sum, r2_sum;
115 	int i;
116 
117 	x_sum = 0.0, y_sum = 0.0, xy_sum = 0.0, x2_sum = 0.0;
118 
119 	for (i = 0; i < n; i++) {
120 		x = samples[i].time;
121 		y = samples[i].offset;
122 
123 		x_sum += x;
124 		y_sum += y;
125 		xy_sum += x * y;
126 		x2_sum += x * x;
127 	}
128 
129 	*slope = (xy_sum - x_sum * y_sum / n) / (x2_sum - x_sum * x_sum / n);
130 	*intercept = (y_sum - *slope * x_sum) / n;
131 
132 	*r_max = 0.0, r2_sum = 0.0;
133 
134 	for (i = 0; i < n; i++) {
135 		x = samples[i].time;
136 		y = samples[i].offset;
137 		r = fabs(x * *slope + *intercept - y);
138 		if (*r_max < r)
139 			*r_max = r;
140 		r2_sum += r * r;
141 	}
142 
143 	*r_stddev = sqrt(r2_sum / n);
144 }
145 
146 static int run_test(int calibration, double freq_base, double freq_step)
147 {
148 	struct sample samples[SAMPLES];
149 	double intercept, slope, stddev1, max1, stddev2, max2;
150 	double freq_error1, freq_error2;
151 	int i;
152 
153 	set_frequency(freq_base);
154 
155 	for (i = 0; i < 10; i++)
156 		usleep(1e6 * MEAN_SAMPLE_INTERVAL / 10);
157 
158 	reset_ntp_error();
159 
160 	set_frequency(freq_base + freq_step);
161 
162 	for (i = 0; i < 10; i++)
163 		usleep(rand() % 2000000 * STEP_INTERVAL / 10);
164 
165 	set_frequency(freq_base);
166 
167 	for (i = 0; i < SAMPLES; i++) {
168 		usleep(rand() % 2000000 * MEAN_SAMPLE_INTERVAL);
169 		get_sample(&samples[i]);
170 	}
171 
172 	if (calibration) {
173 		regress(samples, SAMPLES, &intercept, &slope, &stddev1, &max1);
174 		mono_freq_offset = slope;
175 		printf("CLOCK_MONOTONIC_RAW frequency offset: %11.3f ppm\n",
176 		       1e6 * mono_freq_offset);
177 		return 0;
178 	}
179 
180 	regress(samples, SAMPLES / 2, &intercept, &slope, &stddev1, &max1);
181 	freq_error1 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
182 			freq_base;
183 
184 	regress(samples + SAMPLES / 2, SAMPLES / 2, &intercept, &slope,
185 		&stddev2, &max2);
186 	freq_error2 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
187 			freq_base;
188 
189 	printf("%6.0f %+10.3f %6.0f %7.0f %+10.3f %6.0f %7.0f\t",
190 	       1e6 * freq_step,
191 	       1e6 * freq_error1, 1e9 * stddev1, 1e9 * max1,
192 	       1e6 * freq_error2, 1e9 * stddev2, 1e9 * max2);
193 
194 	if (fabs(freq_error2) > MAX_FREQ_ERROR || stddev2 > MAX_STDDEV) {
195 		printf("[FAIL]\n");
196 		return 1;
197 	}
198 
199 	printf("[OK]\n");
200 	return 0;
201 }
202 
203 static void init_test(void)
204 {
205 	struct timespec ts;
206 	struct sample sample;
207 
208 	if (clock_gettime(CLOCK_MONOTONIC_RAW, &ts)) {
209 		perror("[FAIL] clock_gettime(CLOCK_MONOTONIC_RAW)");
210 		ksft_exit_fail();
211 	}
212 
213 	mono_raw_base = ts.tv_sec;
214 
215 	if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
216 		perror("[FAIL] clock_gettime(CLOCK_MONOTONIC)");
217 		ksft_exit_fail();
218 	}
219 
220 	mono_base = ts.tv_sec;
221 
222 	user_hz = sysconf(_SC_CLK_TCK);
223 
224 	precision = get_sample(&sample) / 2.0;
225 	printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t",
226 	       1e9 * precision);
227 
228 	if (precision > MAX_PRECISION)
229 		ksft_exit_skip("precision: %.0f ns > MAX_PRECISION: %.0f ns\n",
230 				1e9 * precision, 1e9 * MAX_PRECISION);
231 
232 	printf("[OK]\n");
233 	srand(ts.tv_sec ^ ts.tv_nsec);
234 
235 	run_test(1, 0.0, 0.0);
236 }
237 
238 int main(int argc, char **argv)
239 {
240 	double freq_base, freq_step;
241 	int i, j, fails = 0;
242 
243 	init_test();
244 
245 	printf("Checking response to frequency step:\n");
246 	printf("  Step           1st interval              2nd interval\n");
247 	printf("             Freq    Dev     Max       Freq    Dev     Max\n");
248 
249 	for (i = 2; i >= 0; i--) {
250 		for (j = 0; j < 5; j++) {
251 			freq_base = (rand() % (1 << 24) - (1 << 23)) / 65536e6;
252 			freq_step = 10e-6 * (1 << (6 * i));
253 			fails += run_test(0, freq_base, freq_step);
254 		}
255 	}
256 
257 	set_frequency(0.0);
258 
259 	if (fails)
260 		return ksft_exit_fail();
261 
262 	return ksft_exit_pass();
263 }
264