Release 4.7 tools/testing/selftests/timers/adjtick.c
/* adjtimex() tick adjustment test
* by: John Stultz <john.stultz@linaro.org>
* (C) Copyright Linaro Limited 2015
* Licensed under the GPLv2
*
* To build:
* $ gcc adjtick.c -o adjtick -lrt
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/timex.h>
#include <time.h>
#ifdef KTEST
#include "../kselftest.h"
#else
static inline int ksft_exit_pass(void)
{
exit(0);
}
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static inline int ksft_exit_fail(void)
{
exit(1);
}
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#endif
#define CLOCK_MONOTONIC_RAW 4
#define NSEC_PER_SEC 1000000000LL
#define USEC_PER_SEC 1000000
#define MILLION 1000000
long systick;
long long llabs(long long val)
{
if (val < 0)
val = -val;
return val;
}
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unsigned long long ts_to_nsec(struct timespec ts)
{
return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
}
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struct timespec nsec_to_ts(long long ns)
{
struct timespec ts;
ts.tv_sec = ns/NSEC_PER_SEC;
ts.tv_nsec = ns%NSEC_PER_SEC;
return ts;
}
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long long diff_timespec(struct timespec start, struct timespec end)
{
long long start_ns, end_ns;
start_ns = ts_to_nsec(start);
end_ns = ts_to_nsec(end);
return end_ns - start_ns;
}
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void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)
{
struct timespec start, mid, end;
long long diff = 0, tmp;
int i;
clock_gettime(CLOCK_MONOTONIC, mon);
clock_gettime(CLOCK_MONOTONIC_RAW, raw);
/* Try to get a more tightly bound pairing */
for (i = 0; i < 3; i++) {
long long newdiff;
clock_gettime(CLOCK_MONOTONIC, &start);
clock_gettime(CLOCK_MONOTONIC_RAW, &mid);
clock_gettime(CLOCK_MONOTONIC, &end);
newdiff = diff_timespec(start, end);
if (diff == 0 || newdiff < diff) {
diff = newdiff;
*raw = mid;
tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2;
*mon = nsec_to_ts(tmp);
}
}
}
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long long get_ppm_drift(void)
{
struct timespec mon_start, raw_start, mon_end, raw_end;
long long delta1, delta2, eppm;
get_monotonic_and_raw(&mon_start, &raw_start);
sleep(15);
get_monotonic_and_raw(&mon_end, &raw_end);
delta1 = diff_timespec(mon_start, mon_end);
delta2 = diff_timespec(raw_start, raw_end);
eppm = (delta1*MILLION)/delta2 - MILLION;
return eppm;
}
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int check_tick_adj(long tickval)
{
long long eppm, ppm;
struct timex tx1;
tx1.modes = ADJ_TICK;
tx1.modes |= ADJ_OFFSET;
tx1.modes |= ADJ_FREQUENCY;
tx1.modes |= ADJ_STATUS;
tx1.status = STA_PLL;
tx1.offset = 0;
tx1.freq = 0;
tx1.tick = tickval;
adjtimex(&tx1);
sleep(1);
ppm = ((long long)tickval * MILLION)/systick - MILLION;
printf("Estimating tick (act: %ld usec, %lld ppm): ", tickval, ppm);
eppm = get_ppm_drift();
printf("%lld usec, %lld ppm", systick + (systick * eppm / MILLION), eppm);
tx1.modes = 0;
adjtimex(&tx1);
if (tx1.offset || tx1.freq || tx1.tick != tickval) {
printf(" [ERROR]\n");
printf("\tUnexpected adjtimex return values, make sure ntpd is not running.\n");
return -1;
}
/*
* Here we use 100ppm difference as an error bound.
* We likely should see better, but some coarse clocksources
* cannot match the HZ tick size accurately, so we have a
* internal correction factor that doesn't scale exactly
* with the adjustment, resulting in > 10ppm error during
* a 10% adjustment. 100ppm also gives us more breathing
* room for interruptions during the measurement.
*/
if (llabs(eppm - ppm) > 100) {
printf(" [FAILED]\n");
return -1;
}
printf(" [OK]\n");
return 0;
}
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int main(int argv, char **argc)
{
struct timespec raw;
long tick, max, interval, err;
struct timex tx1;
err = 0;
setbuf(stdout, NULL);
if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {
printf("ERR: NO CLOCK_MONOTONIC_RAW\n");
return -1;
}
printf("Each iteration takes about 15 seconds\n");
systick = sysconf(_SC_CLK_TCK);
systick = USEC_PER_SEC/sysconf(_SC_CLK_TCK);
max = systick/10; /* +/- 10% */
interval = max/4; /* in 4 steps each side */
for (tick = (systick - max); tick < (systick + max); tick += interval) {
if (check_tick_adj(tick)) {
err = 1;
break;
}
}
/* Reset things to zero */
tx1.modes = ADJ_TICK;
tx1.modes |= ADJ_OFFSET;
tx1.modes |= ADJ_FREQUENCY;
tx1.offset = 0;
tx1.freq = 0;
tx1.tick = systick;
adjtimex(&tx1);
if (err)
return ksft_exit_fail();
return ksft_exit_pass();
}
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