1/* CLOCK_MONOTONIC vs CLOCK_MONOTONIC_RAW skew test
2 *		by: john stultz (johnstul@us.ibm.com)
3 *		    John Stultz <john.stultz@linaro.org>
4 *		(C) Copyright IBM 2012
5 *		(C) Copyright Linaro Limited 2015
6 *		Licensed under the GPLv2
7 *
8 *  To build:
9 *	$ gcc raw_skew.c -o raw_skew -lrt
10 *
11 *   This program is free software: you can redistribute it and/or modify
12 *   it under the terms of the GNU General Public License as published by
13 *   the Free Software Foundation, either version 2 of the License, or
14 *   (at your option) any later version.
15 *
16 *   This program is distributed in the hope that it will be useful,
17 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
18 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19 *   GNU General Public License for more details.
20 */
21
22#include <stdio.h>
23#include <unistd.h>
24#include <stdlib.h>
25#include <sys/time.h>
26#include <sys/timex.h>
27#include <time.h>
28#ifdef KTEST
29#include "../kselftest.h"
30#else
31static inline int ksft_exit_pass(void)
32{
33	exit(0);
34}
35static inline int ksft_exit_fail(void)
36{
37	exit(1);
38}
39#endif
40
41
42#define CLOCK_MONOTONIC_RAW		4
43#define NSEC_PER_SEC 1000000000LL
44
45#define shift_right(x, s) ({		\
46	__typeof__(x) __x = (x);	\
47	__typeof__(s) __s = (s);	\
48	__x < 0 ? -(-__x >> __s) : __x >> __s; \
49})
50
51long long llabs(long long val)
52{
53	if (val < 0)
54		val = -val;
55	return val;
56}
57
58unsigned long long ts_to_nsec(struct timespec ts)
59{
60	return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
61}
62
63struct timespec nsec_to_ts(long long ns)
64{
65	struct timespec ts;
66
67	ts.tv_sec = ns/NSEC_PER_SEC;
68	ts.tv_nsec = ns%NSEC_PER_SEC;
69	return ts;
70}
71
72long long diff_timespec(struct timespec start, struct timespec end)
73{
74	long long start_ns, end_ns;
75
76	start_ns = ts_to_nsec(start);
77	end_ns = ts_to_nsec(end);
78	return end_ns - start_ns;
79}
80
81void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)
82{
83	struct timespec start, mid, end;
84	long long diff = 0, tmp;
85	int i;
86
87	for (i = 0; i < 3; i++) {
88		long long newdiff;
89
90		clock_gettime(CLOCK_MONOTONIC, &start);
91		clock_gettime(CLOCK_MONOTONIC_RAW, &mid);
92		clock_gettime(CLOCK_MONOTONIC, &end);
93
94		newdiff = diff_timespec(start, end);
95		if (diff == 0 || newdiff < diff) {
96			diff = newdiff;
97			*raw = mid;
98			tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2;
99			*mon = nsec_to_ts(tmp);
100		}
101	}
102}
103
104int main(int argv, char **argc)
105{
106	struct timespec mon, raw, start, end;
107	long long delta1, delta2, interval, eppm, ppm;
108	struct timex tx1, tx2;
109
110	setbuf(stdout, NULL);
111
112	if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {
113		printf("ERR: NO CLOCK_MONOTONIC_RAW\n");
114		return -1;
115	}
116
117	tx1.modes = 0;
118	adjtimex(&tx1);
119	get_monotonic_and_raw(&mon, &raw);
120	start = mon;
121	delta1 = diff_timespec(mon, raw);
122
123	if (tx1.offset)
124		printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");
125
126	printf("Estimating clock drift: ");
127	sleep(120);
128
129	get_monotonic_and_raw(&mon, &raw);
130	end = mon;
131	tx2.modes = 0;
132	adjtimex(&tx2);
133	delta2 = diff_timespec(mon, raw);
134
135	interval = diff_timespec(start, end);
136
137	/* calculate measured ppm between MONOTONIC and MONOTONIC_RAW */
138	eppm = ((delta2-delta1)*NSEC_PER_SEC)/interval;
139	eppm = -eppm;
140	printf("%lld.%i(est)", eppm/1000, abs((int)(eppm%1000)));
141
142	/* Avg the two actual freq samples adjtimex gave us */
143	ppm = (tx1.freq + tx2.freq) * 1000 / 2;
144	ppm = (long long)tx1.freq * 1000;
145	ppm = shift_right(ppm, 16);
146	printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
147
148	if (llabs(eppm - ppm) > 1000) {
149		printf("	[FAILED]\n");
150		return ksft_exit_fail();
151	}
152	printf("	[OK]\n");
153	return  ksft_exit_pass();
154}
155