linux/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>

#include "../kselftest.h"

#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;
}

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;

	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);
		}
	}
}

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;
}

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;
}

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();
}