Improve adjtime() functionality

arch/arm/Kconfig

@@ -429,6 +429,7 @@ config ARCH_CHIP_STM32
 	select ARCH_HAVE_TIMEKEEPING
 	select ARM_HAVE_MPU_UNIFIED
 	select ARMV7M_HAVE_STACKCHECK
+	select ARCH_HAVE_ADJTIME
 	---help---
 		STMicro STM32 architectures (ARM Cortex-M3/4).
 

arch/arm/src/stm32/stm32_timerisr.c

@@ -58,16 +58,19 @@
                                    /* And I don't know now to re-configure it yet */
 
 #ifdef CONFIG_STM32_SYSTICK_HCLKd8
-#  define SYSTICK_RELOAD ((STM32_HCLK_FREQUENCY / 8 / CLK_TCK) - 1)
+#  define SYSTICK_CLOCK  (STM32_HCLK_FREQUENCY / 8)
 #else
-#  define SYSTICK_RELOAD ((STM32_HCLK_FREQUENCY / CLK_TCK) - 1)
+#  define SYSTICK_CLOCK  (STM32_HCLK_FREQUENCY)
 #endif
 
+#define SYSTICK_RELOAD ((SYSTICK_CLOCK / CLK_TCK) - 1)
+
 /* The size of the reload field is 24 bits.  Verify that the reload value
  * will fit in the reload register.
  */
 
-#if SYSTICK_RELOAD > 0x00ffffff
+#define SYSTICK_MAX 0x00ffffff
+#if SYSTICK_RELOAD > SYSTICK_MAX
 #  error SYSTICK_RELOAD exceeds the range of the RELOAD register
 #endif
 
@@ -98,6 +101,69 @@ static int stm32_timerisr(int irq, uint32_t *regs, void *arg)
  * Public Functions
  ****************************************************************************/
 
+#ifdef CONFIG_CLOCK_ADJTIME
+
+/****************************************************************************
+ * Function:  up_adj_timer_period
+ *
+ * Description:
+ *   Adjusts timer period. This call is used when adjusting timer period as
+ *   defined in adjtime() function.
+ *
+ * Input Parameters:
+ *   period_inc_usec  - period adjustment in usec (reset to default value
+ *                      if 0)
+ *
+ ****************************************************************************/
+
+void up_adj_timer_period(long long period_inc_usec)
+{
+  uint32_t period;
+  long long period_inc;
+
+  if (period_inc_usec == 0)
+    {
+      period_inc = 0;
+    }
+  else
+    {
+      period_inc = (SYSTICK_CLOCK / 1000000) * period_inc_usec - 1;
+    }
+
+  period = SYSTICK_RELOAD + period_inc;
+
+  /* Check whether period is at maximum value. */
+
+  if (period > SYSTICK_MAX)
+    {
+      period = SYSTICK_MAX;
+    }
+
+  putreg32(period, NVIC_SYSTICK_RELOAD);
+}
+
+/****************************************************************************
+ * Function:  up_get_timer_period
+ *
+ * Description:
+ *   This function returns the timer period in usec.
+ *
+ * Input Parameters:
+ *   period_usec  - returned timer period in usec
+ *
+ ****************************************************************************/
+
+void up_get_timer_period(long long *period_usec)
+{
+  uint32_t period;
+
+  period = getreg32(NVIC_SYSTICK_RELOAD);
+
+  *period_usec = ((period + 1) / (SYSTICK_CLOCK / 1000000));
+}
+
+#endif
+
 /****************************************************************************
  * Function:  up_timer_initialize
  *

sched/Kconfig

@@ -217,28 +217,24 @@ config CLOCK_ADJTIME
 
 if CLOCK_ADJTIME
 
-config CLOCK_ADJTIME_SLEWLIMIT
+config CLOCK_ADJTIME_SLEWLIMIT_PPM
 	int "Adjtime slew limit"
-	default 2
-	range 0 100
+	default 20000
+	range 1 1000000
 	---help---
-		In real time systems we do not want the time to adjust too quickly.
-		CLOCK_ADJTIME_SLEWLIMIT defines how many seconds can time change
-		during each clock.
+		Set limit of adjtime() clock slewing as parts per million.
 
-		Note that CLOCK_ADJTIME_SLEWLIMIT is divided by 100 in source code,
-		therefore CLOCK_ADJTIME_SLEWLIMIT=2 will result in possible 0.02 second
-		adjustment.
+		In real time systems we do not want the time to adjust too quickly.
+		For example CLOCK_ADJTIME_SLEWLIMIT=1000 will slow or speed the timer
+		tick period by at most 0.1 percent of the nominal value.
 
-config CLOCK_ADJTIME_PERIOD
+config CLOCK_ADJTIME_PERIOD_MS
 	int "Adjtime period"
-	default 97
-	range 0 100
+	default 970
+	range 1 3600000
 	---help---
-		Define system clock adjustment period. Should be between 0.95 and 0.99.
-
-		Note that CLOCK_ADJTIME_PERIOD is divided by 100 in source code,
-		therefore CLOCK_ADJTIME_PERIOD=97 will result in 0.97.
+		Define system clock adjustment period in milliseconds.
+		The adjustment commanded by adjtime() call is applied over this time period.
 
 endif
 

sched/clock/clock_adjtime.c

@@ -51,17 +51,6 @@
         is enabled!
 #endif
 
-/* Set slew limit. In real time systems we don't want the time to adjust
- * too quickly. ADJTIME_SLEWLIMIT defines how many seconds can time change
- * during each clock.
- */
-
-#define ADJTIME_SLEWLIMIT      (CONFIG_CLOCK_ADJTIME_SLEWLIMIT * 0.01)
-
-/* Define system clock adjustment period. */
-
-#define ADJTIME_PERIOD         (CONFIG_CLOCK_ADJTIME_PERIOD    * 0.01)
-
 /****************************************************************************
  * Private Data
  ****************************************************************************/
@@ -158,15 +147,16 @@ int adjtime(FAR const struct timeval *delta, FAR struct timeval *olddelta)
    * of cycles over which we want to do the adjustment.
    */
 
-  count = (USEC_PER_SEC * ADJTIME_PERIOD) / period_usec;
+  count = (USEC_PER_MSEC * CONFIG_CLOCK_ADJTIME_PERIOD_MS) / period_usec;
   incr = adjust_usec / count;
 
   /* Compute maximum possible period increase and check
    * whether previously computed increase exceeds the maximum
    * one.
    */
 
-  incr_limit = ADJTIME_SLEWLIMIT * period_usec;
+  incr_limit = CONFIG_CLOCK_ADJTIME_SLEWLIMIT_PPM
+               / (USEC_PER_SEC / period_usec);
   if (incr > incr_limit)
     {
       /* It does... limit computed increase and increment count. */
@@ -175,20 +165,28 @@ int adjtime(FAR const struct timeval *delta, FAR struct timeval *olddelta)
       count = adjust_usec / incr;
     }
 
+  /* If requested adjustment is smaller than 1 microsecond per tick,
+   * adjust the count instead.
+   */
+
+  if (adjust_usec == 0)
+    {
+      incr = 0;
+      count = 0;
+    }
+  else if (incr == 0)
+    {
+      incr = 1;
+      count = adjust_usec / incr;
+    }
+
   if (is_negative == 1)
     {
       /* Positive or negative? */
 
       incr = -incr;
     }
 
-  /* Ignore small differences. */
-
-  if (incr == 0)
-    {
-      count = 0;
-    }
-
   leave_critical_section(flags);
 
   /* Initialize clock adjustment and get old adjust values. */