selftests/timers: Add clock skew estimation test from timetest suite

This adds my clock skew estimation test from the timetest suite.
It measures the drift between CLOCK_MONOTONIC and CLOCK_MONOTONIC_RAW
and compares it with the current frequency value from adjtimex.

It sometimes can trigger false failures when ntpd isn't in a
steady state, but its a useful too when doing adjtimex testing.

Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Tested-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/timers/Makefile

@@ -2,7 +2,7 @@ CC = $(CROSS_COMPILE)gcc
 BUILD_FLAGS = -DKTEST
 CFLAGS += -O3 -Wl,-no-as-needed -Wall $(BUILD_FLAGS)
 LDFLAGS += -lrt -lpthread
-bins = posix_timers nanosleep inconsistency-check nsleep-lat
+bins = posix_timers nanosleep inconsistency-check nsleep-lat raw_skew
 
 all: ${bins}
 
@@ -11,5 +11,6 @@ run_tests: all
 	./nanosleep
 	./nsleep-lat
 	./inconsistency-check
+	./raw_skew
 clean:
 	rm -f ${bins}

tools/testing/selftests/timers/raw_skew.c

@@ -0,0 +1,154 @@
+/* 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();
+}