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 ksft_exit_fail();
261
262 ksft_exit_pass();
263 }
264
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.