linux-kernel - [PATCHv7 13/16] pps: capture MONOTONIC

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Date:	Mon, 20 Dec 2010 14:54:53 +0300
From:	Alexander Gordeev <lasaine@....cs.msu.su>
To:	linux-kernel@...r.kernel.org
Cc:	"Nikita V\. Youshchenko" <yoush@...msu.su>,
	linuxpps@...enneenne.com, Rodolfo Giometti <giometti@...eenne.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Gordeev <lasaine@....cs.msu.su>,
	John Stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Howells <dhowells@...hat.com>,
	"H\. Peter Anvin" <hpa@...or.com>,
	Magnus Damm <damm@...nsource.se>,
	Jason Wessel <jason.wessel@...driver.com>
Subject: [PATCHv7 13/16] pps: capture MONOTONIC_RAW timestamps as well

MONOTONIC_RAW clock timestamps are ideally suited for frequency
calculation and also fit well into the original NTP hardpps design. Now
phase and frequency can be adjusted separately: the former based on
REALTIME clock and the latter based on MONOTONIC_RAW clock.
A new function getnstime_raw_and_real is added to timekeeping subsystem
to capture both timestamps at the same time and atomically.

Acked-by: John Stultz <johnstul@...ibm.com>
Signed-off-by: Alexander Gordeev <lasaine@....cs.msu.su>
---
 include/linux/pps_kernel.h |   14 ++++++++++++++
 include/linux/time.h       |    2 ++
 kernel/time/timekeeping.c  |   43 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 0 deletions(-)

diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index 1aedf50..9404854 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -47,6 +47,9 @@ struct pps_source_info {
 };
 
 struct pps_event_time {
+#ifdef CONFIG_NTP_PPS
+	struct timespec ts_raw;
+#endif /* CONFIG_NTP_PPS */
 	struct timespec ts_real;
 };
 
@@ -97,10 +100,21 @@ static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
 	kt->nsec = ts.tv_nsec;
 }
 
+#ifdef CONFIG_NTP_PPS
+
+static inline void pps_get_ts(struct pps_event_time *ts)
+{
+	getnstime_raw_and_real(&ts->ts_raw, &ts->ts_real);
+}
+
+#else /* CONFIG_NTP_PPS */
+
 static inline void pps_get_ts(struct pps_event_time *ts)
 {
 	getnstimeofday(&ts->ts_real);
 }
 
+#endif /* CONFIG_NTP_PPS */
+
 #endif /* LINUX_PPS_KERNEL_H */
 
diff --git a/include/linux/time.h b/include/linux/time.h
index 9f15ac7..1e6d3b5 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -158,6 +158,8 @@ extern unsigned int alarm_setitimer(unsigned int seconds);
 extern int do_getitimer(int which, struct itimerval *value);
 extern void getnstimeofday(struct timespec *tv);
 extern void getrawmonotonic(struct timespec *ts);
+extern void getnstime_raw_and_real(struct timespec *ts_raw,
+		struct timespec *ts_real);
 extern void getboottime(struct timespec *ts);
 extern void monotonic_to_bootbased(struct timespec *ts);
 
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 49010d8..5c4be30 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -284,6 +284,49 @@ void ktime_get_ts(struct timespec *ts)
 }
 EXPORT_SYMBOL_GPL(ktime_get_ts);
 
+#ifdef CONFIG_NTP_PPS
+
+/**
+ * getnstime_raw_and_real - get day and raw monotonic time in timespec format
+ * @ts_raw:	pointer to the timespec to be set to raw monotonic time
+ * @ts_real:	pointer to the timespec to be set to the time of day
+ *
+ * This function reads both the time of day and raw monotonic time at the
+ * same time atomically and stores the resulting timestamps in timespec
+ * format.
+ */
+void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
+{
+	unsigned long seq;
+	s64 nsecs_raw, nsecs_real;
+
+	WARN_ON_ONCE(timekeeping_suspended);
+
+	do {
+		u32 arch_offset;
+
+		seq = read_seqbegin(&xtime_lock);
+
+		*ts_raw = raw_time;
+		*ts_real = xtime;
+
+		nsecs_raw = timekeeping_get_ns_raw();
+		nsecs_real = timekeeping_get_ns();
+
+		/* If arch requires, add in gettimeoffset() */
+		arch_offset = arch_gettimeoffset();
+		nsecs_raw += arch_offset;
+		nsecs_real += arch_offset;
+
+	} while (read_seqretry(&xtime_lock, seq));
+
+	timespec_add_ns(ts_raw, nsecs_raw);
+	timespec_add_ns(ts_real, nsecs_real);
+}
+EXPORT_SYMBOL(getnstime_raw_and_real);
+
+#endif /* CONFIG_NTP_PPS */
+
 /**
  * do_gettimeofday - Returns the time of day in a timeval
  * @tv:		pointer to the timeval to be set
-- 
1.7.2.3

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