Cosmetic changed, updated README files, improved comments

arch/arm/src/sama5/sam_tickless.c

@@ -54,6 +54,27 @@
  *     logic when the interval timer expires.
  *
  ****************************************************************************/
+/****************************************************************************
+ * SAMA5 Timer Usage
+ *
+ * This current implementation uses two timers:  A one-shot timer to provide
+ * the timed events and a free running timer to provide the current time.
+ * Since timers are a limited resource, that could be an issue on some
+ * systems.
+ *
+ * We could do the job with a single timer if we were to keep the single
+ * timer in a free-running at all times.  The SAMA5 timer/counters have
+ * 32-bit counters with the capability to generate a compare interrupt when
+ * the timer matches a compare value but also to continue counting without
+ * stopping (giving another, different interrupt when the timer rolls over
+ * from 0xffffffff to zero).  So we could potentially just set the compare
+ * at the number of ticks you want PLUS the current value of timer.  Then
+ * you could have both with a single timer:  An interval timer and a free-
+ * running counter with the same timer!
+ *
+ * Patches are welcome!
+ *
+ ****************************************************************************/
 
 /****************************************************************************
  * Included Files

configs/sama5d3-xplained/README.txt

@@ -2332,6 +2332,8 @@ TRNG and /dev/random
 Tickless OS
 ===========
 
+  Background
+  ----------
   By default, a NuttX configuration uses a periodic timer interrupt that
   drives all system timing. The timer is provided by architecture-specifi
   code that calls into NuttX at a rate controlled by CONFIG_USEC_PER_TICK.
@@ -2368,6 +2370,8 @@ Tickless OS
   OS event will occur, program the interval time and wait for it to fire.
   When the interval time fires, then the scheduled activity is performed.
 
+  Configuration
+  -------------
   The following configuration options will enable support for the Tickless
   OS for the SAMA5D platforms using TC0 channels 0-3 (other timers or
   timer channels could be used making the obvious substitutions):
@@ -2385,6 +2389,25 @@ Tickless OS
       CONFIG_SAMA5_TICKLESS_FREERUN=1  : Selects TC0 channel 1 for the free-
                                        : running timer
 
+  SAMA5 Timer Usage
+  -----------------
+  This current implementation uses two timers:  A one-shot timer to
+  provide the timed events and a free running timer to provide the current
+  time.  Since timers are a limited resource, that could be an issue on
+  some systems.
+
+  We could do the job with a single timer if we were to keep the single
+  timer in a free-running at all times.  The SAMA5 timer/counters have
+  32-bit counters with the capability to generate a compare interrupt when
+  the timer matches a compare value but also to continue counting without
+  stopping (giving another, different interrupt when the timer rolls over
+  from 0xffffffff to zero).  So we could potentially just set the compare
+  at the number of ticks you want PLUS the current value of timer.  Then
+  you could have both with a single timer:  An interval timer and a free-
+  running counter with the same timer!
+
+  Patches are welcome!
+
 I2S Audio Support
 =================
 

configs/sama5d3x-ek/README.txt

@@ -2648,6 +2648,8 @@ Touchscreen Testing
 Tickless OS
 ===========
 
+  Background
+  ----------
   By default, a NuttX configuration uses a periodic timer interrupt that
   drives all system timing. The timer is provided by architecture-specifi
   code that calls into NuttX at a rate controlled by CONFIG_USEC_PER_TICK.
@@ -2684,6 +2686,8 @@ Tickless OS
   OS event will occur, program the interval time and wait for it to fire.
   When the interval time fires, then the scheduled activity is performed.
 
+  Configuration
+  -------------
   The following configuration options will enable support for the Tickless
   OS for the SAMA5D platforms using TC0 channels 0-3 (other timers or
   timer channels could be used making the obvious substitutions):
@@ -2701,6 +2705,25 @@ Tickless OS
       CONFIG_SAMA5_TICKLESS_FREERUN=1  : Selects TC0 channel 1 for the free-
                                        : running timer
 
+  SAMA5 Timer Usage
+  -----------------
+  This current implementation uses two timers:  A one-shot timer to
+  provide the timed events and a free running timer to provide the current
+  time.  Since timers are a limited resource, that could be an issue on
+  some systems.
+
+  We could do the job with a single timer if we were to keep the single
+  timer in a free-running at all times.  The SAMA5 timer/counters have
+  32-bit counters with the capability to generate a compare interrupt when
+  the timer matches a compare value but also to continue counting without
+  stopping (giving another, different interrupt when the timer rolls over
+  from 0xffffffff to zero).  So we could potentially just set the compare
+  at the number of ticks you want PLUS the current value of timer.  Then
+  you could have both with a single timer:  An interval timer and a free-
+  running counter with the same timer!
+
+  Patches are welcome!
+
 OV2640 Camera Interface
 =======================
 

configs/sama5d4-ek/README.txt

@@ -3112,6 +3112,8 @@ TM7000 LCD/Touchscreen
 Tickless OS
 ===========
 
+  Background
+  ----------
   By default, a NuttX configuration uses a periodic timer interrupt that
   drives all system timing. The timer is provided by architecture-specifi
   code that calls into NuttX at a rate controlled by CONFIG_USEC_PER_TICK.
@@ -3148,6 +3150,8 @@ Tickless OS
   OS event will occur, program the interval time and wait for it to fire.
   When the interval time fires, then the scheduled activity is performed.
 
+  Configuration
+  -------------
   The following configuration options will enable support for the Tickless
   OS for the SAMA5D platforms using TC0 channels 0-3 (other timers or
   timer channels could be used making the obvious substitutions):
@@ -3165,6 +3169,25 @@ Tickless OS
       CONFIG_SAMA5_TICKLESS_FREERUN=1  : Selects TC0 channel 1 for the free-
                                        : running timer
 
+  SAMA5 Timer Usage
+  -----------------
+  This current implementation uses two timers:  A one-shot timer to
+  provide the timed events and a free running timer to provide the current
+  time.  Since timers are a limited resource, that could be an issue on
+  some systems.
+
+  We could do the job with a single timer if we were to keep the single
+  timer in a free-running at all times.  The SAMA5 timer/counters have
+  32-bit counters with the capability to generate a compare interrupt when
+  the timer matches a compare value but also to continue counting without
+  stopping (giving another, different interrupt when the timer rolls over
+  from 0xffffffff to zero).  So we could potentially just set the compare
+  at the number of ticks you want PLUS the current value of timer.  Then
+  you could have both with a single timer:  An interval timer and a free-
+  running counter with the same timer!
+
+  Patches are welcome!
+
 SAMA4D4-EK Configuration Options
 =================================