Primary purpose of rtc_show_time is to provide a marker used for
post-mortem Battery and Power analysis. These markers occur at
major discontinuities of time, and thus optionally add a timestamp
to aid the analysis. This function is to be called at a higher
level, and were added because of a lack of current kernel logging
data.
The persistent clock that is used to report Suspended for message
is not present on all platforms, and is currently standardized for
millisecond precision.
An added value to the time report is the ability in post-mortem
triage analysis to synchronize kernel activities in MONOTONIC
time with user space activities in REALTIME.
Feature activated by CONFIG_RTC_SHOW_TIME_<TYPE>, where <TYPE> is
None (default, disabled), realtime, boottime or monotonic.
Since this is for post mortem field analysis, there is no debugfs
or trace facility that can generally be leveraged. analyze_suspend.py
for example requires a debug configured kernel, on the other hand
these prints can remain in a field product. The purpose for
rtc_show_time is not for development debugging.
Data collected may be recorded by klogd with a longer logspan
than the built-in dmesg buffer, or land in pstore console driver
to be collected after a reboot.
Signed-off-by: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
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
v4:
- introduce CONFIG_RTC_SHOW_TIME_<TYPE> and split off rtc time
format printing to a separate patch.
---
include/linux/rtc.h | 5 +++
kernel/time/Kconfig | 77 +++++++++++++++++++++++++++++++++++++++++++++
kernel/time/Makefile | 1 +
kernel/time/rtc_show_time.c | 29 +++++++++++++++++
4 files changed, 112 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..2dc891056635 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -145,3 +145,80 @@ config HIGH_RES_TIMERS
endmenu
endif
+
+config RTC_SHOW_TIME
+ bool
+ help
+ Activate optional rtc_show_time(const char *msg) wall clock
+ time instrumentation.
+
+ The primary use of the instrumentation is to aid field
+ analysis of Battery and Power usage. The instrumentation
+ may also help triage and synchronize kernel logs and user
+ space activity logs at key displacements. For instance
+ CLOCK_MONOTONIC stops while suspended, while CLOCK_REALTIME
+ continues, and the timestamps help re-orient post-analysis.
+
+ Select the appropriate RTC_SHOW_TIME_<type>
+
+choice
+ prompt "choose a clock for rtc_show_time"
+ config RTC_SHOW_TIME_NONE
+ bool "not activated"
+ help
+ Turn off all printing associated with rtc_show_time
+
+ The primary use of the instrumentation is to aid field
+ analysis of Battery and Power usage. The instrumentation
+ may also help triage and synchronize kernel logs and user
+ space activity logs at key displacements. For instance
+ CLOCK_MONOTONIC stops while suspended, while CLOCK_REALTIME
+ continues, and the timestamps help re-orient post-analysis.
+
+ This is the default behavior.
+ config RTC_SHOW_TIME_REALTIME
+ bool "realtime"
+ select RTC_SHOW_TIME
+ help
+ Activate optional rtc_show_time(const char *msg) wall clock
+ time instrumentation.
+
+ The primary use of the instrumentation is to aid field
+ analysis of Battery and Power usage. The instrumentation
+ may also help triage and synchronize kernel logs and user
+ space activity logs at key displacements. For instance
+ CLOCK_MONOTONIC stops while suspended, while CLOCK_REALTIME
+ continues, and the timestamps help re-orient post-analysis.
+
+ Print realtime <epoch>.<ns> timestamp in rtc_show_time
+ config RTC_SHOW_TIME_MONOTONIC
+ bool "monotonic"
+ select RTC_SHOW_TIME
+ help
+ Activate optional rtc_show_time(const char *msg) wall clock
+ time instrumentation.
+
+ The primary use of the instrumentation is to aid field
+ analysis of Battery and Power usage. The instrumentation
+ may also help triage and synchronize kernel logs and user
+ space activity logs at key displacements. For instance
+ CLOCK_MONOTONIC stops while suspended, while CLOCK_REALTIME
+ continues, and the timestamps help re-orient post-analysis.
+
+ Print only the supplied message in rtc_show_time
+ config RTC_SHOW_TIME_BOOTTIME
+ bool "boottime"
+ select RTC_SHOW_TIME
+ help
+ Activate optional rtc_show_time(const char *msg) wall clock
+ time instrumentation.
+
+ The primary use of the instrumentation is to aid field
+ analysis of Battery and Power usage. The instrumentation
+ may also help triage and synchronize kernel logs and user
+ space activity logs at key displacements. For instance
+ CLOCK_MONOTONIC stops while suspended, while CLOCK_REALTIME
+ continues, and the timestamps help re-orient post-analysis.
+
+ Print boottime <s>.<ns> timestamp in rtc_show_time
+endchoice
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..19a8a0cc94f0
--- /dev/null
+++ b/kernel/time/rtc_show_time.c
@@ -0,0 +1,29 @@
+/*
+ * 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)
+{
+#if defined(CONFIG_RTC_SHOW_TIME_MONOTONIC) /* dmesg is in monotonic */
+ pr_info("%s\n", prefix_msg ? prefix_msg : "Time:");
+#elif defined(CONFIG_RTC_SHOW_TIME_BOOTTIME)
+ struct timespec64 ts;
+
+ getboottime64(&ts);
+ pr_info("%s %lu.%09lu B\n",
+ prefix_msg ? prefix_msg : "Time:", ts.tv_sec, ts.tv_nsec);
+#else /* realtime */
+ struct timespec64 ts;
+
+ getnstimeofday64(&ts);
+ pr_info("%s %lu.%09lu UTC\n",
+ prefix_msg ? prefix_msg : "Time:", ts.tv_sec, ts.tv_nsec);
+#endif
+}
+EXPORT_SYMBOL(rtc_show_time);
--
2.14.0.rc0.284.gd933b75aa4-goog
