From e8358031666c5d6036c702da0dcf3c82ad94d946 Mon Sep 17 00:00:00 2001
From: Jussi Kivilinna <jussi.kivilinna@haltian.com>
Date: Wed, 26 Apr 2017 10:38:15 -0600
Subject: [PATCH] yslog: use monotonic clock for timestamp when available

---
 drivers/syslog/vsyslog.c       | 20 +++++++++++++++++---
 sched/clock/clock_initialize.c |  3 ++-
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/syslog/vsyslog.c b/drivers/syslog/vsyslog.c
index 27fab399ec..ba0d3726f8 100644
--- a/drivers/syslog/vsyslog.c
+++ b/drivers/syslog/vsyslog.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * drivers/syslog/vsyslog.c
  *
- *   Copyright (C) 2007-2009, 2011-2014, 2016 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011-2014, 2016-2017 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -70,15 +70,29 @@ int _vsyslog(int priority, FAR const IPTR char *fmt, FAR va_list *ap)
   struct lib_outstream_s stream;
 #ifdef CONFIG_SYSLOG_TIMESTAMP
   struct timespec ts;
+  int ret = -1;
 
   /* Get the current time.  Since debug output may be generated very early
    * in the start-up sequence, hardware timer support may not yet be
    * available.
    */
 
-  if (!OSINIT_HW_READY() || clock_systimespec(&ts) < 0)
+  if (OSINIT_HW_READY())
     {
-      /* Timer hardware is not available, or clock_systimespec failed */
+      /* Prefer monotonic when enabled, as it can be synchronized to
+       * RTC with clock_resynchronize.
+       */
+
+#ifdef CONFIG_CLOCK_MONOTONIC
+      ret = clock_gettime(CLOCK_MONOTONIC, &ts);
+#else
+      ret = clock_systimespec(&ts);
+#endif
+    }
+
+  if (ret < 0)
+    {
+      /* Timer hardware is not available, or clock function failed */
 
       ts.tv_sec  = 0;
       ts.tv_nsec = 0;
diff --git a/sched/clock/clock_initialize.c b/sched/clock/clock_initialize.c
index d8a7b13497..ca565c9c8a 100644
--- a/sched/clock/clock_initialize.c
+++ b/sched/clock/clock_initialize.c
@@ -68,7 +68,8 @@
 #define SEC_PER_HOUR ((time_t)60 * SEC_PER_MIN)
 #define SEC_PER_DAY  ((time_t)24 * SEC_PER_HOUR)
 
-#if defined(CONFIG_DEBUG_FEATURES) && defined(CONFIG_SYSTEM_TIME64)
+#if defined(CONFIG_DEBUG_FEATURES) && defined(CONFIG_SYSTEM_TIME64) && \
+    defined(CONFIG_CLOCK_MONOTONIC)
 /* Initial system timer ticks value close to maximum 32-bit value, to test
  * 64-bit system-timer after going over 32-bit value. This is to make errors
  * of casting 64-bit system-timer to 32-bit variables more visible.