Update comments

arch/arm/src/sama5/Kconfig

@@ -3586,7 +3586,11 @@ config SAMA5_TC_DEBUG
 	default n
 	---help---
 		Output high level Timer/Counter device debug information.
-		Requires also DEBUG.
+		Requires also DEBUG.  If this option AND DEBUG_VERBOSE are
+		enabled, then the system will be overwhelmed the timer debug
+		output.  If DEBUG_VERBOSE is disabled, then debug output will
+		only indicate if/when timer-related errors occur.  This
+		latter mode is completely usable.
 
 config SAMA5_TC_REGDEBUG
 	bool "TC register level debug"

include/nuttx/arch.h

@@ -1049,7 +1049,8 @@ int up_timer_gettime(FAR struct timespec *ts);
  *
  * Input Parameters:
  *   ts - Location to return the remaining time.  Zero should be returned
- *        if the timer is not active.
+ *        if the timer is not active.  ts may be zero in which case the
+ *        time remaining is not returned.
  *
  * Returned Value:
  *   Zero (OK) is returned on success.  A call to up_timer_cancel() when