1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
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
40struct sample {
41 double offset;
42 double time;
43};
44
45static time_t mono_raw_base;
46static time_t mono_base;
47static long user_hz;
48static double precision;
49static double mono_freq_offset;
50
51static 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
56static 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
88static 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
102static 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
119static 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
154static 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
211static 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
246int 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
