linux-kernel - [PATCH 1/3] time: Don't bother to run rtc

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Date:	Tue, 20 Jan 2015 16:41:28 +0000
From:	Xunlei Pang <pang.xunlei@...aro.org>
To:	linux-kernel@...r.kernel.org
Cc:	rtc-linux@...glegroups.com, Thomas Gleixner <tglx@...utronix.de>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Feng Tang <feng.tang@...el.com>,
	John Stultz <john.stultz@...aro.org>,
	Arnd Bergmann <arnd.bergmann@...aro.org>,
	Xunlei Pang <pang.xunlei@...aro.org>
Subject: [PATCH 1/3] time: Don't bother to run rtc_resume() for nonstop clocksource

If a system does not provide a persistent_clock(), the time will be
updated on resume by rtc_resume(). With the addition of the non-stop
clocksources for suspend timing, those systems set the time on resume
in timekeeping_resume(), but may not provide a valid persistent_clock().

This results in the rtc_resume() logic thinking no one has set the time
and it then will over-write the suspend time again, which is not necessary
and only increases clock error.

So, fix this for rtc_resume().

Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org>
---
 drivers/rtc/class.c         |  2 +-
 include/linux/timekeeping.h | 11 +++++++++++
 kernel/time/timekeeping.c   |  3 ++-
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 472a5ad..c8f35a5 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev)
 	struct timespec64	sleep_time;
 	int err;
 
-	if (has_persistent_clock())
+	if (rtc_resume_skip())
 		return 0;
 
 	rtc_hctosys_ret = -ENODEV;
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 9b63d13..6f3283b 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -238,6 +238,17 @@ extern void getnstime_raw_and_real(struct timespec *ts_raw,
  */
 extern bool persistent_clock_exist;
 extern int persistent_clock_is_local;
+extern bool suspendtime_found;
+
+#ifdef CONFIG_RTC_LIB
+/* Used by rtc_resume() */
+static inline bool rtc_resume_skip(void)
+{
+	return suspendtime_found;
+}
+#else
+static inline void rtc_resume_skip(void) { }
+#endif
 
 static inline bool has_persistent_clock(void)
 {
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 6a93185..586bb5c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -65,6 +65,7 @@ int __read_mostly timekeeping_suspended;
 
 /* Flag for if there is a persistent clock on this platform */
 bool __read_mostly persistent_clock_exist = false;
+bool suspendtime_found;
 
 static inline void tk_normalize_xtime(struct timekeeper *tk)
 {
@@ -1178,8 +1179,8 @@ static void timekeeping_resume(void)
 	struct timespec64 ts_new, ts_delta;
 	struct timespec tmp;
 	cycle_t cycle_now, cycle_delta;
-	bool suspendtime_found = false;
 
+	suspendtime_found = false;
 	read_persistent_clock(&tmp);
 	ts_new = timespec_to_timespec64(tmp);
 
-- 
1.9.1

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