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/* CLOCK_MONOTONIC vs CLOCK_MONOTONIC_RAW skew test
* by: john stultz (johnstul@us.ibm.com)
* John Stultz <john.stultz@linaro.org>
* (C) Copyright IBM 2012
* (C) Copyright Linaro Limited 2015
* Licensed under the GPLv2
*
* To build:
* $ gcc raw_skew.c -o raw_skew -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);
}
static inline int ksft_exit_fail(void)
{
exit(1);
}
#endif
#define CLOCK_MONOTONIC_RAW 4
#define NSEC_PER_SEC 1000000000LL
#define shift_right(x, s) ({ \
__typeof__(x) __x = (x); \
__typeof__(s) __s = (s); \
__x < 0 ? -(-__x >> __s) : __x >> __s; \
})
long long llabs(long long val)
{
if (val < 0)
val = -val;
return val;
}
unsigned long long ts_to_nsec(struct timespec ts)
{
return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
}
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;
}
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;
}
void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)
{
struct timespec start, mid, end;
long long diff = 0, tmp;
int i;
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);
}
}
}
int main(int argv, char **argc)
{
struct timespec mon, raw, start, end;
long long delta1, delta2, interval, eppm, ppm;
struct timex tx1, tx2;
setbuf(stdout, NULL);
if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {
printf("ERR: NO CLOCK_MONOTONIC_RAW\n");
return -1;
}
tx1.modes = 0;
adjtimex(&tx1);
get_monotonic_and_raw(&mon, &raw);
start = mon;
delta1 = diff_timespec(mon, raw);
if (tx1.offset)
printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");
printf("Estimating clock drift: ");
sleep(120);
get_monotonic_and_raw(&mon, &raw);
end = mon;
tx2.modes = 0;
adjtimex(&tx2);
delta2 = diff_timespec(mon, raw);
interval = diff_timespec(start, end);
/* calculate measured ppm between MONOTONIC and MONOTONIC_RAW */
eppm = ((delta2-delta1)*NSEC_PER_SEC)/interval;
eppm = -eppm;
printf("%lld.%i(est)", eppm/1000, abs((int)(eppm%1000)));
/* Avg the two actual freq samples adjtimex gave us */
ppm = (tx1.freq + tx2.freq) * 1000 / 2;
ppm = (long long)tx1.freq * 1000;
ppm = shift_right(ppm, 16);
printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
if (llabs(eppm - ppm) > 1000) {
printf(" [FAILED]\n");
return ksft_exit_fail();
}
printf(" [OK]\n");
return ksft_exit_pass();
}
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