1 /* adjtimex() tick adjustment test 2 * by: John Stultz <john.stultz (at) linaro.org> 3 * (C) Copyright Linaro Limited 2015 4 * Licensed under the GPLv2 5 * 6 * To build: 7 * $ gcc adjtick.c -o adjtick -lrt 8 * 9 * This program is free software: you can redistribute it and/or modify 10 * it under the terms of the GNU General Public License as published by 11 * the Free Software Foundation, either version 2 of the License, or 12 * (at your option) any later version. 13 * 14 * This program is distributed in the hope that it will be useful, 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 * GNU General Public License for more details. 18 */ 19 #include <stdio.h> 20 #include <unistd.h> 21 #include <stdlib.h> 22 #include <sys/time.h> 23 #include <sys/timex.h> 24 #include <time.h> 25 26 #include "../kselftest.h" 27 28 #define CLOCK_MONOTONIC_RAW 4 29 30 #define NSEC_PER_SEC 1000000000LL 31 #define USEC_PER_SEC 1000000 32 33 #define MILLION 1000000 34 35 long systick; 36 37 long long llabs(long long val) 38 { 39 if (val < 0) 40 val = -val; 41 return val; 42 } 43 44 unsigned long long ts_to_nsec(struct timespec ts) 45 { 46 return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec; 47 } 48 49 struct timespec nsec_to_ts(long long ns) 50 { 51 struct timespec ts; 52 53 ts.tv_sec = ns/NSEC_PER_SEC; 54 ts.tv_nsec = ns%NSEC_PER_SEC; 55 56 return ts; 57 } 58 59 long long diff_timespec(struct timespec start, struct timespec end) 60 { 61 long long start_ns, end_ns; 62 63 start_ns = ts_to_nsec(start); 64 end_ns = ts_to_nsec(end); 65 66 return end_ns - start_ns; 67 } 68 69 void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw) 70 { 71 struct timespec start, mid, end; 72 long long diff = 0, tmp; 73 int i; 74 75 clock_gettime(CLOCK_MONOTONIC, mon); 76 clock_gettime(CLOCK_MONOTONIC_RAW, raw); 77 78 /* Try to get a more tightly bound pairing */ 79 for (i = 0; i < 3; i++) { 80 long long newdiff; 81 82 clock_gettime(CLOCK_MONOTONIC, &start); 83 clock_gettime(CLOCK_MONOTONIC_RAW, &mid); 84 clock_gettime(CLOCK_MONOTONIC, &end); 85 86 newdiff = diff_timespec(start, end); 87 if (diff == 0 || newdiff < diff) { 88 diff = newdiff; 89 *raw = mid; 90 tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2; 91 *mon = nsec_to_ts(tmp); 92 } 93 } 94 } 95 96 long long get_ppm_drift(void) 97 { 98 struct timespec mon_start, raw_start, mon_end, raw_end; 99 long long delta1, delta2, eppm; 100 101 get_monotonic_and_raw(&mon_start, &raw_start); 102 103 sleep(15); 104 105 get_monotonic_and_raw(&mon_end, &raw_end); 106 107 delta1 = diff_timespec(mon_start, mon_end); 108 delta2 = diff_timespec(raw_start, raw_end); 109 110 eppm = (delta1*MILLION)/delta2 - MILLION; 111 112 return eppm; 113 } 114 115 int check_tick_adj(long tickval) 116 { 117 long long eppm, ppm; 118 struct timex tx1; 119 120 tx1.modes = ADJ_TICK; 121 tx1.modes |= ADJ_OFFSET; 122 tx1.modes |= ADJ_FREQUENCY; 123 tx1.modes |= ADJ_STATUS; 124 125 tx1.status = STA_PLL; 126 tx1.offset = 0; 127 tx1.freq = 0; 128 tx1.tick = tickval; 129 130 adjtimex(&tx1); 131 132 sleep(1); 133 134 ppm = ((long long)tickval * MILLION)/systick - MILLION; 135 printf("Estimating tick (act: %ld usec, %lld ppm): ", tickval, ppm); 136 137 eppm = get_ppm_drift(); 138 printf("%lld usec, %lld ppm", systick + (systick * eppm / MILLION), eppm); 139 140 tx1.modes = 0; 141 adjtimex(&tx1); 142 143 if (tx1.offset || tx1.freq || tx1.tick != tickval) { 144 printf(" [ERROR]\n"); 145 printf("\tUnexpected adjtimex return values, make sure ntpd is not running.\n"); 146 return -1; 147 } 148 149 /* 150 * Here we use 100ppm difference as an error bound. 151 * We likely should see better, but some coarse clocksources 152 * cannot match the HZ tick size accurately, so we have a 153 * internal correction factor that doesn't scale exactly 154 * with the adjustment, resulting in > 10ppm error during 155 * a 10% adjustment. 100ppm also gives us more breathing 156 * room for interruptions during the measurement. 157 */ 158 if (llabs(eppm - ppm) > 100) { 159 printf(" [FAILED]\n"); 160 return -1; 161 } 162 printf(" [OK]\n"); 163 164 return 0; 165 } 166 167 int main(int argv, char **argc) 168 { 169 struct timespec raw; 170 long tick, max, interval, err; 171 struct timex tx1; 172 173 err = 0; 174 setbuf(stdout, NULL); 175 176 if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) { 177 printf("ERR: NO CLOCK_MONOTONIC_RAW\n"); 178 return -1; 179 } 180 181 printf("Each iteration takes about 15 seconds\n"); 182 183 systick = sysconf(_SC_CLK_TCK); 184 systick = USEC_PER_SEC/sysconf(_SC_CLK_TCK); 185 max = systick/10; /* +/- 10% */ 186 interval = max/4; /* in 4 steps each side */ 187 188 for (tick = (systick - max); tick < (systick + max); tick += interval) { 189 if (check_tick_adj(tick)) { 190 err = 1; 191 break; 192 } 193 } 194 195 /* Reset things to zero */ 196 tx1.modes = ADJ_TICK; 197 tx1.modes |= ADJ_OFFSET; 198 tx1.modes |= ADJ_FREQUENCY; 199 200 tx1.offset = 0; 201 tx1.freq = 0; 202 tx1.tick = systick; 203 204 adjtimex(&tx1); 205 206 if (err) 207 return ksft_exit_fail(); 208 209 return ksft_exit_pass(); 210 } 211
