Add support for lo- and hi-res RTC hardware

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4005 42af7a65-404d-4744-a932-0658087f49c3

ChangeLog

@@ -2121,3 +2121,8 @@
 	* configs/sam3u/touchscreen - This is the configuration that I plan to use
 	  to verify the SAM3U-EK touchscreen driver.  However, as of this writing,
 	  there is no touchscreen driver for the board.
+	* CONFIG_RTC_HIRES - Add an option to support either a high-resolution RTC
+	  that completely replaces the system timer tick but may overflow and lose
+	  time when the MCU is off and also for a low-resolution (1 sec/tick) RTC
+	  that can run until 2106 with no overflow.  But in this latter case, higher
+	  resolution time must come from the system timer.

Documentation/NuttxPortingGuide.html

@@ -12,7 +12,7 @@
       <h1><big><font color="#3c34ec">
         <i>NuttX RTOS Porting Guide</i>
       </font></big></h1>
-      <p>Last Updated: September 13, 2011</p>
+      <p>Last Updated: October 1, 2011</p>
     </td>
   </tr>
 </table>
@@ -1989,18 +1989,30 @@ CONFIG_SYSTEM_UTC=y
 
 <h4>4.1.20.2 Hardware</h4>
 <p>
-  To enable hardware module use option:
+  To enable hardware module use the following configuration options:
 <p>
-<ul><pre>
+<ul><dl>
-CONFIG_RTC=y
+  <dt><code>CONFIG_RTC</code>
-</pre></ul>
+  <dd>Enables general support for a hardware RTC. 
+      Specific architectures may require other specific settings.
+  <dt><code>CONFIG_RTC_HIRES</code>
+  <dd>The typical RTC keeps time to resolution of 1 second, usually supporting a 32-bit <code>time_t</code> value.
+      In this case, the RTC is used to &quot;seed&quot; the normal NuttX timer and the NuttX timer provides for higher resoution time.
+      If <code>CONFIG_RTC_HIRES</code> is enabled in the NuttX configuration, then the RTC provides higher resolution time and completely replaces the system timer for purpose of date and time.
+  <dt><code>CONFIG_RTC_FREQUENCY</code>
+  <dd>If <code>CONFIG_RTC_HIRES</code> is defined, then the frequency of the high resolution RTC must be provided.
+      If <code>CONFIG_RTC_HIRES</code> is not defined, <code>CONFIG_RTC_FREQUENCY</code> is assumed to be one.
+  <dt><code>CONFIG_RTC_ALARM</code>
+  <dd>Enable if the RTC hardware supports setting of an alarm. 
+    A callback function will be executed when the alarm goes off
+</dl></ul>
 <p>
   which requires the following three base functions to read time:
 </p>
 <ul>
   <li><code>up_rtcinitialize()</code></li>
-  <li><code>up_rtc_gettime()</code>. UTC time in seconds.</li>
+  <li><code>up_rtc_time()</code>. UTC time in seconds.</li>
-  <li><code>up_rtc_getclock()</code>. Replacement for <code>g_system_tick</code></li>
+  <li><code>up_rtc_gettime()</code>. Replacement for <code>g_system_tick</code></li>
 </ul>
 <p>
   This module depends on <code>CONFIG_SYSTEM_UTC=y</code>.
@@ -2024,15 +2036,17 @@ CONFIG_RTC=y
   Running at rate of system base timer, used for time-slicing, and so forth.
 </p>
 <p>
-  If hardware RTC is present (<code>CONFIG_RTC</code>) and enabled, then after successful
+  If hardware RTC is present (<code>CONFIG_RTC</code>) and and high-resolution timeing
-  initiliazation variables are overriden by calls to <code>up_rtc_getclock()</code> which is
+  is enabled (<code>CONFIG_RTC_HIRES</code>), then after successful
+  initiliazation variables are overriden by calls to <code>up_rtc_gettime()</code> which is
   running continously even in power-down modes.
 </p>
 <p>
-  In the case of <code>CONFIG_RTC</code> is set the <code>g_tickcount</code> and <code>g_system_utc</code> keep
+  In the case of <code>CONFIG_RTC_HIRES</code> is set the <code>g_tickcount</code> and
-  counting at rate of a system timer, which however, is disabled in power-down
+  <code>g_system_utc</code> keep counting at rate of a system timer, which however, is
-  mode. By comparing this time and RTC (actual time) one may determine the
+  disabled in power-down mode.
-  actual system active time. To retrieve that variable use:
+  By comparing this time and RTC (actual time) one may determine the actual system active time.
+  To retrieve that variable use:
 </p>
 <ul><pre>
   <li><code>clock_gettime(CLOCK_ACTIVETIME, tp)</code>
@@ -4239,10 +4253,35 @@ build
 </ul>
 
 <h2>Device Drivers</h2>
+<h3>RTC</h3>
+<ul>
+  <li>
+    <code>CONFIG_RTC</code>:
+      Enables general support for a hardware RTC. 
+      Specific architectures may require other specific settings.
+  </li>
+  <li>
+    <code>CONFIG_RTC_HIRES</code>:
+      The typical RTC keeps time to resolution of 1 second, usually supporting a 32-bit <code>time_t</code> value.
+      In this case, the RTC is used to &quot;seed&quot; the normal NuttX timer and the NuttX timer provides for higher resoution time.
+      If <code>CONFIG_RTC_HIRES</code> is enabled in the NuttX configuration, then the RTC provides higher resolution time and completely replaces the system timer for purpose of date and time.
+  </li>
+  <li>
+    <code>CONFIG_RTC_FREQUENCY</code>:
+      If <code>CONFIG_RTC_HIRES</code> is defined, then the frequency of the high resolution RTC must be provided.
+      If <code>CONFIG_RTC_HIRES</code> is not defined, <code>CONFIG_RTC_FREQUENCY</code> is assumed to be one.
+  </li>
+  <li>
+    <code>CONFIG_RTC_ALARM</code>:
+      Enable if the RTC hardware supports setting of an alarm. 
+      A callback function will be executed when the alarm goes off
+  </li>
+</ul>
+
 <h3>SPI driver</h3>
 <ul>
   <li>
-    <code>CONFIG_SPI_OWNBUS</code> - Set if there is only one active device
+    <code>CONFIG_SPI_OWNBUS</code>: Set if there is only one active device
     on the SPI bus.  No locking or SPI configuration will be performed.
     It is not necessary for clients to lock, re-configure, etc..
   </li>

arch/arm/src/stm32/stm32_i2c.c

@@ -6,6 +6,7 @@
  *
  * With extensions, modifications by:
  *
+ *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregroy Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -932,7 +933,7 @@ static inline void stm32_i2c_enablefsmc(uint32_t ahbenr)
     }
 }
 #else
-#  define stm32_i2c_disablefsmc() (0)
+#  define stm32_i2c_disablefsmc(priv) (0)
 #  define stm32_i2c_enablefsmc(ahbenr)
 #endif
 

configs/vsn/nsh/defconfig

@@ -268,6 +268,7 @@ CONFIG_WIRELESS=y
 #
 CONFIG_RTC=y
 CONFIG_RTC_HIRES=y
+CONFIG_RTC_FREQUENCY=16384
 CONFIG_SYSTEM_UTC=y
 
 #

configs/vsn/src/sif.c

@@ -714,9 +714,8 @@ int sif_main(int argc, char *argv[])
     struct timespec t_active;
     clock_gettime(CLOCK_ACTIVETIME, &t_active);
     
-    fprintf(stderr, "rtc time = %u / %u, active = %u / %u, time / systick = %u / %u\n", 
+    fprintf(stderr, "rtc time = %u, active = %u / %u, time / systick = %u / %u\n", 
-        up_rtc_gettime(), up_rtc_getclock(),
+        up_rtc_time(), t_active.tv_sec, t_active.tv_nsec,
-        t_active.tv_sec, t_active.tv_nsec,
         time(NULL), clock_systimer() );
     return -1;
 }

include/nuttx/clock.h

@@ -172,7 +172,7 @@ extern "C" {
  *
  ****************************************************************************/
 
-#if defined(CONFIG_RTC) || !__HAVE_KERNEL_GLOBALS
+#if defined(CONFIG_SYSTEM_UTC) || !__HAVE_KERNEL_GLOBALS
 EXTERN uint32_t clock_systimer(void);
 #endif
 

include/nuttx/rtc.h

@@ -4,6 +4,11 @@
  *   Copyright(C) 2011 Uros Platise. All rights reserved.
  *   Author: Uros Platise <uros.platise@isotel.eu>
  *
+ * With extensions, modifications by:
+ *
+ *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
+ *   Author: Gregroy Nutt <gnutt@nuttx.org>
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -44,19 +49,51 @@
 
 #include <stdint.h>
 #include <stdbool.h>
-
+#include <time.h>
-#include <nuttx/clock.h>
 
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
+/* Configuration ************************************************************/
+/* CONFIG_RTC - Enables general support for a hardware RTC.  Specific
+ *   architectures may require other specific settings.
+ *
+ * CONFIG_RTC_HIRES - The typical RTC keeps time to resolution of 1 second,
+ *   usually supporting a 32-bit time_t value.  In this case, the RTC is
+ *   used to "seed" the normal NuttX timer and the NuttX timer provides
+ *   for higher resoution time.
+ *
+ *   If CONFIG_RTC_HIRES is enabled in the NuttX configuration, then the
+ *   RTC provides higher resolution time and completely replaces the system
+ *   timer for purpose of date and time.
+ *
+ * CONFIG_RTC_FREQUENCY - If CONFIG_RTC_HIRES is defined, then the frequency
+ *   of the high resolution RTC must be provided.  If CONFIG_RTC_HIRES is
+ *   not defined, CONFIG_RTC_FREQUENCY is assumed to be one.
+ *
+ * CONFIG_RTC_ALARM - Enable if the RTC hardware supports setting of an
+ *   alarm.  A callback function will be executed when the alarm goes off
+ */
 
-#define RTC_CLOCKS_PER_SEC      16384
+#ifdef CONFIG_RTC_HIRES
-#define RTC_CLOCKS_SHIFT        14
+#  ifndef CONFIG_RTC_FREQUENCY
+#    error "CONFIG_RTC_FREQUENCY is required for CONFIG_RTC_HIRES"
+#  endif
+#else
+#  ifndef CONFIG_RTC_FREQUENCY
+#    define CONFIG_RTC_FREQUENCY 1
+#  endif
+#  if CONFIG_RTC_FREQUENCY != 1
+#    error "The low resolution RTC must have frequency 1Hz"
+#  endif
+#endif
 
 /****************************************************************************
  * Public Types
  ****************************************************************************/
+/* The form of an alarm callback */
+
+typedef void (alarmcb_t)(void);
 
 /****************************************************************************
  * Public Variables
@@ -83,32 +120,92 @@ extern "C" {
 #define EXTERN extern
 #endif
 
-/****************************************************************************
+/************************************************************************************
  * Name: up_rtcinitialize
  *
  * Description:
- *   Initialize the periodic timer interface. This function is called once
+ *   Initialize the hardware RTC per the select configuration.  This function is
- *   from the clock_initialize() function.
+ *   called once during the OS initialization sequence
+ *
+ * Input Parameters:
+ *   None
  *
  * Returned Value:
- *   Returns OK if RTC has successfully started, otherwise ERROR.
+ *   Zero (OK) on success; a negated errno on failure
  *
- ****************************************************************************/
+ ************************************************************************************/
 
 EXTERN int up_rtcinitialize(void);
-EXTERN int up_rtcinitialize(void);
 
-EXTERN clock_t up_rtc_getclock(void);
+/************************************************************************************
-EXTERN void up_rtc_setclock(clock_t clock);
+ * Name: up_rtc_time
+ *
+ * Description:
+ *   Get the current time in seconds.  This is similar to the standard time()
+ *   function.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   The current time in seconds
+ *
+ ************************************************************************************/
 
-EXTERN time_t up_rtc_gettime(void);
+EXTERN time_t up_rtc_time(void);
-EXTERN void up_rtc_settime(time_t time);
 
-EXTERN clock_t up_rtc_setalarm(clock_t atclock);
+/************************************************************************************
+ * Name: up_rtc_gettime
+ *
+ * Description:
+ *   Get the current time from the high resolution RTC clock.
+ *
+ * Input Parameters:
+ *   tp - The location to return the high resolution time value.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno on failure
+ *
+ ************************************************************************************/
 
-/* This callback is provided by the clock module and called by the RTC ISR */
+#ifdef CONFIG_RTC_HIRES
+EXTERN int up_rtc_gettime(FAR struct timespec *tp);
+#endif
 
-EXTERN void clock_rtcalarmcb(clock_t clock);
+/************************************************************************************
+ * Name: up_rtc_settime
+ *
+ * Description:
+ *   Set the RTC to the provided time.
+ *
+ * Input Parameters:
+ *   tp - the time to use
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno on failure
+ *
+ ************************************************************************************/
+
+EXTERN int up_rtc_settime(FAR const struct timespec *tp);
+
+/************************************************************************************
+ * Name: up_rtc_setalarm
+ *
+ * Description:
+ *   Set up a alarm.
+ *
+ * Input Parameters:
+ *   tp - the time to set the alarm
+ *   callback - the function to call when the alarm expires.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno on failure
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_RTC_ALARM
+EXTERN int up_rtc_setalarm(FAR const struct timespec *tp, alarmcb_t callback);
+#endif
 
 #undef EXTERN
 #if defined(__cplusplus)

include/time.h

@@ -77,7 +77,7 @@
  * power down modes. Unit is 1 second.
  */
 
-#ifdef CONFIG_RTC
+#ifdef CONFIG_SYSTEM_UTC
 #  define CLOCK_ACTIVETIME 1
 #endif
 

sched/clock_gettime.c

@@ -113,7 +113,12 @@ int clock_gettime(clockid_t clock_id, struct timespec *tp)
 
   if (clock_id == CLOCK_REALTIME && tp)
     {
+      /* If CONFIG_SYSTEM_UTC is not defined, then we have to get the time
+       * from g_system_timer.
+       */
+
 #ifndef CONFIG_SYSTEM_UTC
+
       /* Get the elapsed time since power up (in milliseconds) biased
        * as appropriate.
        */
@@ -151,47 +156,18 @@ int clock_gettime(clockid_t clock_id, struct timespec *tp)
       tp->tv_sec  = (time_t)secs;
       tp->tv_nsec = (long)nsecs;
       
-#else   /* if CONFIG_SYSTEM_UTC=y */
+#else /* CONFIG_SYSTEM_UTC */
 
-#ifdef CONFIG_RTC
+      /* CONFIG_SYSTEM_UTC is defined.  But we might be able to get the time
+       * from the hardware if a high resolution RTC is available.
+       */
+
+#ifdef CONFIG_RTC_HIRES
       if (g_rtc_enabled)
         {
-          /* up_rtc_gettime() returns the time in seconds and up_rtc_getclock()
+          /* Get the hi-resolution time from the RTC */
-           * will return the time int RTC clock ticks.  Under the hood, these
-           * are probably based on the same running time.  However, since we
-           * sample this time twice, we have to add the following strange logic
-           * to assure that the fractional second value does not rollover to
-           * a full second between sampling times.
-           */
 
-          clock_t rtc_frac; /* Current fractional seconds in RTC ticks */
+          ret = up_rtc_gettime(tp);
-          clock_t rtc_last; /* Previous fractional seconds in RTC ticks */
-          time_t  rtc_sec;  /* Current seconds */
-
-          /* Interrupts are disabled here only to prevent interrupts and context
-           * switches from interfering with the consecutive time samples.  I
-           * expect to go through this loop 1 time 99.9% of the time and then
-           * only twice on the remaining cornercases.
-           */
-
-          flags = irqsave();
-          rtc_frac = up_rtc_getclock() & (RTC_CLOCKS_PER_SEC-1);
-          do
-            {
-              rtc_last = rtc_frac;
-              rtc_sec  = up_rtc_gettime();
-              rtc_frac = up_rtc_getclock() & (RTC_CLOCKS_PER_SEC-1);
-            }
-          while (rtc_frac < rtc_last);
-          irqrestore(flags);
-
-          /* Okay.. the samples should be as close together in time as possible
-           * and we can be assured that no fractional second rollover occurred
-           * between the samples.
-           */
-
-          tp->tv_sec  = rtc_sec;
-          tp->tv_nsec = rtc_frac * (1000000000/RTC_CLOCKS_PER_SEC);
         }
       else
 #endif
@@ -209,17 +185,16 @@ int clock_gettime(clockid_t clock_id, struct timespec *tp)
           tp->tv_sec  = system_utc;
           tp->tv_nsec = tickcount * (1000000000/TICK_PER_SEC);
         }
-#endif
+#endif  /* CONFIG_SYSTEM_UTC */
 
-      sdbg("Returning tp=(%d,%d)\n",
+      sdbg("Returning tp=(%d,%d)\n", (int)tp->tv_sec, (int)tp->tv_nsec);
-           (int)tp->tv_sec, (int)tp->tv_nsec);
     }
 
  /* CLOCK_ACTIVETIME is non-standard. Returns active UTC time, which is
   * disabled during power down modes. Unit is 1 second.
   */
 
-#ifdef CONFIG_RTC
+#ifdef CONFIG_SYSTEM_UTC
   else if (clock_id == CLOCK_ACTIVETIME && g_rtc_enabled && tp)
     {
       /* Disable interrupts while g_system_utc and g_tickcount are sampled

sched/clock_initialize.c

@@ -54,6 +54,12 @@
  * Definitions
  ****************************************************************************/
 
+#ifdef CONFIG_RTC
+#  ifndef CONFIG_SYSTEM_UTC
+#  error "In order to support hardware RTC system must have set the CONFIG_SYSTEM_UTC=y"
+#  endif
+#endif
+
 /* Standard time definitions (in units of seconds) */
 
 #define SEC_PER_MIN  ((time_t)60)
@@ -85,11 +91,11 @@
  ****************************************************************************/
 
 #if CONFIG_SYSTEM_UTC
-volatile time_t  g_system_utc   = 0;
+volatile time_t  g_system_utc;
 #else
-volatile clock_t g_system_timer = 0;
+volatile clock_t g_system_timer;
-struct timespec  g_basetime     = {0,0};
+struct timespec  g_basetime;
-uint32_t         g_tickbias     = 0;
+uint32_t         g_tickbias;
 #endif
 
 /**************************************************************************
@@ -102,11 +108,11 @@ uint32_t         g_tickbias     = 0;
 
 #if CONFIG_SYSTEM_UTC
 #if TICK_PER_SEC > 32767
-volatile uint32_t g_tickcount = 0;
+volatile uint32_t g_tickcount;
 #elif TICK_PER_SEC > 255
-volatile uint16_t g_tickcount = 0;
+volatile uint16_t g_tickcount;
 #else
-volatile uint8_t  g_tickcount = 0;
+volatile uint8_t  g_tickcount;
 #endif
 #endif /* CONFIG_SYSTEM_UTC */
 
@@ -114,7 +120,7 @@ volatile uint8_t  g_tickcount = 0;
  * Private Functions
  **************************************************************************/
 /****************************************************************************
- * Function: clock_timer
+ * Function: incr_utc
  *
  * Description:
  *   This function must be called once every time the real
@@ -139,9 +145,57 @@ static inline void incr_utc(void)
 #endif
 
 /****************************************************************************
- * Private Functions
+ * Function: clock_inittime
+ *
+ * Description:
+ *   Get the initial time value from the best source available.
+ *
  ****************************************************************************/
 
+#ifdef CONFIG_RTC
+#ifdef CONFIG_RTC_HIRES
+
+static inline void clock_inittime(FAR struct timespec *tp)
+{
+
+  /* Get the complete time from the hi-res RTC. */
+
+  (void)up_rtc_gettime(tp);
+}
+
+#else
+
+static inline void clock_inittime(FAR struct timespec *tp)
+{
+  /* Get the seconds (only) from the lo-res RTC */
+
+  tp->tv_sec  = up_rtc_time();
+  tp->tv_nsec = 0;
+}
+
+#endif /* CONFIG_RTC_HIRES */
+#else /* CONFIG_RTC */
+
+static inline void clock_inittime(FAR struct timespec *tp)
+{
+  time_t jdn = 0;
+
+  /* Get the EPOCH-relative julian date from the calendar year,
+   * month, and date
+   */
+
+  jdn = clock_calendar2utc(CONFIG_START_YEAR, CONFIG_START_MONTH,
+                           CONFIG_START_DAY);
+
+  /* Set the base time as seconds into this julian day. */
+
+  tp->tv_sec  = jdn * SEC_PER_DAY;
+  tp->tv_nsec = 0;
+}
+
+#endif /* CONFIG_RTC */
+
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -156,47 +210,25 @@ static inline void incr_utc(void)
 
 void clock_initialize(void)
 {
-#ifndef CONFIG_SYSTEM_UTC
-  time_t jdn = 0;
-#endif
-
-  /* Initialize the real time close (this should be un-nesssary except on a
-   * restart).
-   */
-
 #ifdef CONFIG_SYSTEM_UTC
-  g_system_utc   = 0;
+  struct timespec ts;
-#else
-  g_system_timer = 0;
 #endif
 
-  /* Do we have hardware RTC support? */
+  /* Initialize the RTC hardware */
 
 #ifdef CONFIG_RTC
-
-#ifndef CONFIG_SYSTEM_UTC
-#  error In order to support hardware RTC system must have set the CONFIG_SYSTEM_UTC=y
-#endif
-
   up_rtcinitialize();
 #endif
 
-#ifndef CONFIG_SYSTEM_UTC
+  /* Initialize the time value */
-
-  /* Get the EPOCH-relative julian date from the calendar year,
-   * month, and date
-   */
-
-  jdn = clock_calendar2utc(CONFIG_START_YEAR, CONFIG_START_MONTH,
-                           CONFIG_START_DAY);
-
-  /* Set the base time as seconds into this julian day. */
-
-  g_basetime.tv_sec  = jdn * SEC_PER_DAY;
-  g_basetime.tv_nsec = 0;
-
-  /* These is no time bias from this time. */
 
+#ifdef CONFIG_SYSTEM_UTC
+  clock_inittime(&ts);
+  g_system_utc = ts.tv_sec;
+  g_tickcount  = ((ts.tv_nsec > 10) * CLOCKS_PER_SEC) / (1000000000 >> 10);
+#else
+  clock_inittime(&g_basetime);
+  g_system_timer = 0;
   g_tickbias     = 0;
 #endif
 }

sched/clock_settime.c

@@ -43,6 +43,8 @@
 #include <time.h>
 #include <errno.h>
 #include <debug.h>
+
+#include <arch/irq.h>
 #include "clock_internal.h"
 
 /************************************************************************
@@ -85,7 +87,7 @@
  *
  ************************************************************************/
 
-int clock_settime(clockid_t clock_id, const struct timespec *tp)
+int clock_settime(clockid_t clock_id, FAR const struct timespec *tp)
 {
   int ret = OK;
 
@@ -116,12 +118,13 @@ int clock_settime(clockid_t clock_id, const struct timespec *tp)
 #ifdef CONFIG_RTC
       if (g_rtc_enabled)
         {
-          up_rtc_settime(tp->tv_sec);
+          up_rtc_settime(tp);
         } 
       else
 #endif
+        {
           g_system_utc = tp->tv_sec;
-
+        }
 #endif
 
       sdbg("basetime=(%d,%d) tickbias=%d\n",
@@ -133,10 +136,25 @@ int clock_settime(clockid_t clock_id, const struct timespec *tp)
   * disabled during power down modes. Unit is 1 second.
   */
 
-#ifdef CONFIG_RTC
+#ifdef CONFIG_SYSTEM_UTC
-  else if (clock_id == CLOCK_ACTIVETIME && g_rtc_enabled && tp) 
+  else if (clock_id == CLOCK_ACTIVETIME && tp) 
     {
+      irqstate_t flags;
+      uint32_t tickcount;
+
+      /* Calculate the number of ticks correspond to the nanosecond count...
+       * exercising care to avoid overflows.  This could still overflow
+       * if CLOCKS_PER_SEC is very large (something like 4096).
+       */
+
+      tickcount = ((tp->tv_nsec >> 10) * CLOCKS_PER_SEC) / (1000000000 >> 10);
+
+      /* Then set the UTC time (seconds) plus the tickcount (fractional seconds */
+
+      flags = irqsave();
       g_system_utc = tp->tv_sec;
+      g_tickcount  = tickcount;
+      irqrestore(flags);
     }
 #endif
 

sched/clock_systimer.c

@@ -85,20 +85,12 @@ uint32_t clock_systimer(void)
   uint32_t tickcount;
 #endif
 
-  /* Fetch the g_system_timer value from timer hardware, if available */
+#ifdef CONFIG_RTC_HIRES
-
+  /* Fetch the g_system_timer value from timer hardware, if available.
-#ifdef CONFIG_RTC
-
-  /* Check if the periodic timer is initialized
    *
-   * Note that the unit of the g_system_timer and and up_rtc_getclock() do
+   * Note that the unit of the g_system_timer and and up_rtc_gettime() do
    * not have the same unit.
    */
-
-  if (g_rtc_enabled)
-    {
-      /* return up_rtc_getclock(); */
-    }
 #endif
 
 #ifndef CONFIG_SYSTEM_UTC