Initial import

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

2 files changed, 654 insertions, 0 deletions

diff --git a/COPYING b/COPYING
new file mode 100644
index 0000000..b8db91d
--- /dev/null
+++ b/COPYING
@@ -0,0 +1,353 @@
+Valid-License-Identifier: GPL-2.0
+Valid-License-Identifier: GPL-2.0+
+SPDX-URL: https://spdx.org/licenses/GPL-2.0.html
+Usage-Guide:
+  To use this license in source code, put one of the following SPDX
+  tag/value pairs into a comment according to the placement
+  guidelines in the licensing rules documentation.
+  For 'GNU General Public License (GPL) version 2 only' use:
+    SPDX-License-Identifier: GPL-2.0
+  For 'GNU General Public License (GPL) version 2 or any later version' use:
+    SPDX-License-Identifier: GPL-2.0+
+License-Text:
+
+		    GNU GENERAL PUBLIC LICENSE
+		       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.
+                       51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+			    Preamble
+
+  The licenses for most software are designed to take away your
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+License is intended to guarantee your freedom to share and change free
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+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Library General Public License instead.)  You can apply it to
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+
+  When we speak of free software, we are referring to freedom, not
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+
+		    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
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+
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+
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+
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+
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+		     END OF TERMS AND CONDITIONS
+
+	    How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
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+    <one line to give the program's name and a brief idea of what it does.>
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+    This is free software, and you are welcome to redistribute it
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+The hypothetical commands `show w' and `show c' should show the appropriate
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+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Library General
+Public License instead of this License.
diff --git a/rtc-sync.c b/rtc-sync.c
new file mode 100644
index 0000000..511f2f9
--- /dev/null
+++ b/rtc-sync.c
@@ -0,0 +1,301 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <fcntl.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <linux/rtc.h>
+
+#define NSEC_PER_SEC	1000000000L
+
+int set_realtime_priority(void)
+{
+	int ret;
+	pthread_t this_thread = pthread_self();
+	struct sched_param params;
+
+	params.sched_priority = sched_get_priority_max(SCHED_FIFO);
+	ret = pthread_setschedparam(this_thread, SCHED_FIFO, &params);
+	if (ret != 0)
+		fprintf(stderr, "Unable to set realtime priority\n");
+
+	return ret;
+}
+
+void timespec_diff(struct timespec *start, struct timespec *stop,
+                   struct timespec *result)
+{
+    if ((stop->tv_nsec - start->tv_nsec) < 0) {
+        result->tv_sec = stop->tv_sec - start->tv_sec - 1;
+        result->tv_nsec = stop->tv_nsec - start->tv_nsec + NSEC_PER_SEC;
+    } else {
+        result->tv_sec = stop->tv_sec - start->tv_sec;
+        result->tv_nsec = stop->tv_nsec - start->tv_nsec;
+    }
+
+    return;
+}
+
+int get_offset_uie(struct timespec *diff, int rtc)
+{
+	unsigned long data;
+	struct timespec now;
+	struct tm stm;
+	int rc;
+	int i;
+
+	rc = ioctl(rtc, RTC_UIE_ON, 0);
+	if (rc < 0) {
+		perror("RTC_UIE_ON");
+		return rc;
+	}
+
+	for (i = 0; i < 5; i++) {
+		rc = read(rtc, &data, sizeof(data));
+		if (rc < 0) {
+			perror("read");
+			return rc;
+		}
+		clock_gettime(CLOCK_REALTIME, &now);
+		ioctl(rtc, RTC_RD_TIME, &stm);
+		if (rc < 0) {
+			perror("RTC_RD_TIME");
+			break;
+		}
+		printf("%d %d.%09d\n", timegm(&stm), now.tv_sec, now.tv_nsec);
+	}
+
+	rc = ioctl(rtc, RTC_UIE_OFF, 0);
+	if (rc < 0) {
+		perror("RTC_UIE_OFF");
+		return rc;
+	}
+
+	diff->tv_sec = now.tv_sec - timegm(&stm);
+	diff->tv_nsec = now.tv_nsec;
+
+	return 0;
+}
+
+int get_offset_alarm(struct timespec *diff, int rtc)
+{
+	struct rtc_wkalrm alarm = { 0 };
+	struct timespec now;
+	struct tm stm;
+	time_t secs;
+	unsigned long data;
+	int rc;
+
+	//TODO: save/restore surrent alarm
+
+	rc = ioctl(rtc, RTC_RD_TIME, &stm);
+	if (rc < 0) {
+		perror("RTC_RD_TIME");
+		return rc;
+	}
+
+	secs = timegm(&stm);
+
+	secs++;
+
+	gmtime_r(&secs, &stm);
+
+	alarm.time.tm_sec = stm.tm_sec;
+	alarm.time.tm_min = stm.tm_min;
+	alarm.time.tm_hour = stm.tm_hour;
+	alarm.time.tm_mday = stm.tm_mday;
+	alarm.time.tm_mon = stm.tm_mon;
+	alarm.time.tm_year = stm.tm_year;
+	alarm.time.tm_wday = -1;
+	alarm.time.tm_yday = -1;
+	alarm.time.tm_isdst = -1;
+	alarm.enabled = 1;
+	rc = ioctl(rtc, RTC_WKALM_SET, &alarm);
+	if (rc < 0) {
+		perror("RTC_WKALM_SET");
+		return rc;
+	}
+
+	rc = read(rtc, &data, sizeof(data));
+	if (rc < 0) {
+		perror("read");
+		return rc;
+	}
+
+	clock_gettime(CLOCK_REALTIME, &now);
+
+	rc = ioctl(rtc, RTC_RD_TIME, &stm);
+	if (rc < 0) {
+		perror("RTC_RD_TIME");
+		return rc;
+	}
+
+	secs = timegm(&stm);
+
+	printf("%d %d.%09d\n", secs, now.tv_sec, now.tv_nsec);
+	diff->tv_sec = now.tv_sec - secs;
+	diff->tv_nsec = now.tv_nsec;
+
+	return 0;
+}
+
+int get_offset_poll(struct timespec *diff, int rtc)
+{
+	struct tm stm;
+	struct timespec now;
+	int rc;
+	int i, secs;
+	unsigned long m = 0;
+	struct timespec b, a, d;
+
+	for (i = 0; i < 100; i++) {
+		clock_gettime(CLOCK_MONOTONIC, &b);
+		rc = ioctl(rtc, RTC_RD_TIME, &stm);
+		if (rc < 0) {
+			perror("RTC_RD_TIME");
+			return rc;
+		}
+		clock_gettime(CLOCK_MONOTONIC, &a);
+
+		timespec_diff(&b, &a, &d);
+
+		m += d.tv_nsec/100 + d.tv_sec * 10000000;
+	}
+
+	printf("POLL: Mean time to read: %lu\n", m);
+
+	rc = ioctl(rtc, RTC_RD_TIME, &stm);
+	if (rc < 0) {
+		perror("RTC_RD_TIME");
+		return rc;
+	}
+
+	secs = stm.tm_sec;
+	do {
+		clock_gettime(CLOCK_MONOTONIC, &b);
+		ioctl(rtc, RTC_RD_TIME, &stm);
+		if (rc < 0) {
+			perror("RTC_RD_TIME");
+			return rc;
+		}
+		clock_gettime(CLOCK_MONOTONIC, &a);
+	} while (stm.tm_sec == secs);
+
+	clock_gettime(CLOCK_REALTIME, &now);
+	printf("POLL: corrected: %d %d.%09d\n", timegm(&stm), now.tv_sec, now.tv_nsec - m);
+	timespec_diff(&b, &a, &d);
+	printf("POLL: Last time to read: %lu %d\n", d.tv_nsec, i);
+
+	diff->tv_sec = now.tv_sec - timegm(&stm);
+	diff->tv_nsec = now.tv_nsec - m;
+
+	return 0;
+}
+
+int main(void)
+{
+	struct timespec now, ts, diff;
+	struct tm stm;
+	time_t secs;
+	int rtc;
+	int rc;
+
+	int (*get_offset)(struct timespec *diff, int rtc);
+
+	get_offset = get_offset_alarm;
+
+	clock_getres(CLOCK_REALTIME, &ts);
+	printf("CLOCK_REALTIME %d.%09d\n", ts.tv_sec, ts.tv_nsec);
+	clock_getres(CLOCK_MONOTONIC, &ts);
+	printf("CLOCK_MONOTONIC %d.%09d\n", ts.tv_sec, ts.tv_nsec);
+
+	rtc = open("/dev/rtc0", O_RDONLY);
+	if (rtc < 0) {
+		perror("open");
+		return rtc;
+	}
+
+	set_realtime_priority();
+
+	rc = get_offset(&diff, rtc);
+	if (rc)
+		return rc;
+	printf("Current offset: %ds + %09dns = %dns\n", diff.tv_sec, diff.tv_nsec, diff.tv_sec * NSEC_PER_SEC + diff.tv_nsec);
+
+	clock_gettime(CLOCK_REALTIME, &now);
+
+	/* sleep to the next second unless now is too close */
+	ts.tv_nsec = 0;
+	ts.tv_sec = now.tv_sec + 1;
+	if (ts.tv_nsec > 900000000)
+		ts.tv_sec++;
+
+	gmtime_r(&ts.tv_sec, &stm);
+	printf("setting %d at %d.%09d\n", ts.tv_sec, ts.tv_sec, ts.tv_nsec);
+
+	rc = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &ts, NULL);
+	if (rc) {
+		perror("clock_nanosleep");
+		return rc;
+	}
+
+	rc = ioctl(rtc, RTC_SET_TIME, &stm);
+	if (rc < 0) {
+		perror("RTC_SET_TIME");
+		return rc;
+	}
+
+	rc = get_offset(&diff, rtc);
+	if (rc)
+		return rc;
+	printf("Set offset: %ds + %09dns = %dns\n", diff.tv_sec, diff.tv_nsec, diff.tv_sec * NSEC_PER_SEC + diff.tv_nsec);
+
+	clock_gettime(CLOCK_REALTIME, &now);
+
+	/* Calculate the next full second */
+	if (diff.tv_sec < 0) {
+		/*
+		 * RTC is set earlier than system time unless system time is going
+		 * back, this will never be more than 1s
+		 */
+		secs = now.tv_sec;
+		ts.tv_sec = now.tv_sec;
+		ts.tv_nsec =  NSEC_PER_SEC - diff.tv_nsec;
+	} else {
+		/*
+		 * RTC is late so at the next second minus diff.tv_nsec, we need to set
+		 * the RTC to next second + diff.tv_sec
+		 */
+		ts.tv_sec = now.tv_sec;
+		ts.tv_nsec = NSEC_PER_SEC - diff.tv_nsec;
+		secs = ts.tv_sec + 1 + diff.tv_sec;
+	}
+
+	/* too close, use next second */
+	if (ts.tv_nsec - now.tv_nsec < 100000000) {
+		ts.tv_sec++;
+		secs++;
+	}
+
+	gmtime_r(&secs, &stm);
+	printf("setting %d at %d.%09d\n", secs, ts.tv_sec, ts.tv_nsec);
+
+	clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &ts, NULL);
+
+	rc = ioctl(rtc, RTC_SET_TIME, &stm);
+	if (rc < 0) {
+		perror("RTC_SET_TIME");
+		return rc;
+	}
+
+	rc = get_offset(&diff, rtc);
+	if (rc)
+		return rc;
+	printf("New offset: %ds + %09dns = %dns\n", diff.tv_sec, diff.tv_nsec, diff.tv_sec * NSEC_PER_SEC + diff.tv_nsec);
+
+	return 0;
+}