linux-kernel - [PATCH v3 1/4] time: rtc-lib: Add rtc_show_time(const char *prefix

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Date:   Tue, 18 Jul 2017 15:15:57 -0700
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     linux-kernel@...r.kernel.org
Cc:     rjw@...ysocki.net, len.brown@...el.com, pavel@....cz,
        linux-pm@...r.kernel.org, a.zummo@...ertech.it,
        alexandre.belloni@...e-electrons.com, linux-rtc@...r.kernel.org,
        andy.shevchenko@...il.com, Mark Salyzyn <salyzyn@...roid.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Mark Salyzyn <salyzyn@...gle.com>,
        Thierry Strudel <tstrudel@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>,
        Josh Triplett <josh@...htriplett.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH v3 1/4] time: rtc-lib: Add rtc_show_time(const char *prefix_msg)

Go directly to the rtc for persistent wall clock time and print.
Useful if REALTIME is required to be logged in a low level power
management function or when clock activities are suspended.  An
aid to permit user space alignment of kernel activities.

Feature activated by CONFIG_RTC_SHOW_TIME.

Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>

v2
- move implementation to kernel timekeeping from rtc_lib files
- use rtc_time64_to_tm() instead of rtc_time_to_tm()
- use inline in include/linux/rtc.h for !CONFIG_RTC_SHOW_TIME
v3
- _correctly_ use rtc_time64_to_tm
---
 include/linux/rtc.h         |  5 +++++
 kernel/time/Kconfig         | 11 +++++++++++
 kernel/time/Makefile        |  1 +
 kernel/time/rtc_show_time.c | 23 +++++++++++++++++++++++
 4 files changed, 40 insertions(+)
 create mode 100644 kernel/time/rtc_show_time.c

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 0a0f0d14a5fb..779401c937d5 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -22,6 +22,11 @@ extern int rtc_year_days(unsigned int day, unsigned int month, unsigned int year
 extern int rtc_valid_tm(struct rtc_time *tm);
 extern time64_t rtc_tm_to_time64(struct rtc_time *tm);
 extern void rtc_time64_to_tm(time64_t time, struct rtc_time *tm);
+#ifdef CONFIG_RTC_SHOW_TIME
+extern void rtc_show_time(const char *prefix_msg);
+#else
+static inline void rtc_show_time(const char *prefix_msg) { }
+#endif
 ktime_t rtc_tm_to_ktime(struct rtc_time tm);
 struct rtc_time rtc_ktime_to_tm(ktime_t kt);
 
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index ac09bc29eb08..4da093ae3e37 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -145,3 +145,14 @@ config HIGH_RES_TIMERS
 
 endmenu
 endif
+
+config RTC_SHOW_TIME
+	bool "rtc_show_time instrumentation"
+	select RTC_LIB
+	help
+	  Activate rtc_show_time(const char *msg) wall clock time
+	  instrumentation.
+
+	  The instrumentation is used to help triage and synchronize
+	  kernel logs using CLOCK_MONOTONIC and user space activity
+	  logs utilizing CLOCK_REALTIME references.
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index 938dbf33ef49..66f17e641052 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -17,3 +17,4 @@ obj-$(CONFIG_GENERIC_SCHED_CLOCK)		+= sched_clock.o
 obj-$(CONFIG_TICK_ONESHOT)			+= tick-oneshot.o tick-sched.o
 obj-$(CONFIG_DEBUG_FS)				+= timekeeping_debug.o
 obj-$(CONFIG_TEST_UDELAY)			+= test_udelay.o
+obj-$(CONFIG_RTC_SHOW_TIME)			+= rtc_show_time.o
diff --git a/kernel/time/rtc_show_time.c b/kernel/time/rtc_show_time.c
new file mode 100644
index 000000000000..bbf4f92abf4f
--- /dev/null
+++ b/kernel/time/rtc_show_time.c
@@ -0,0 +1,23 @@
+/*
+ * rtc time printing utility functions
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/rtc.h>
+
+void rtc_show_time(const char *prefix_msg)
+{
+	struct timespec64 ts;
+	struct rtc_time tm;
+
+	getnstimeofday64(&ts);
+	rtc_time64_to_tm(ts.tv_sec, &tm);
+	pr_info("%s %d-%02d-%02d %02d:%02d:%02d.%09lu UTC\n",
+		prefix_msg ? prefix_msg : "Time:",
+		tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+		tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
+}
+EXPORT_SYMBOL(rtc_show_time);
-- 
2.13.2.932.g7449e964c-goog