Replace the static prvSetupTimerInterrupt() function in the Cortex-M port layers that still used it (other than MPU ports so far) with a weakly defined function call vPortSetupTimerInterrupt() - which allows application writers to override the function with one that uses a different clock.

FreeRTOS/Source/portable/GCC/ARM_CM0/port.c

@@ -71,9 +71,11 @@ debugger. */
 #endif
 
 /*
- * Setup the timer to generate the tick interrupts.
+ * Setup the timer to generate the tick interrupts.  The implementation in this
+ * file is weak to allow application writers to change the timer used to
+ * generate the tick interrupt.
  */
-static void prvSetupTimerInterrupt( void );
+void vPortSetupTimerInterrupt( void );
 
 /*
  * Exception handlers.
@@ -217,7 +219,7 @@ BaseType_t xPortStartScheduler( void )
 
 	/* Start the timer that generates the tick ISR.  Interrupts are disabled
 	here already. */
-	prvSetupTimerInterrupt();
+	vPortSetupTimerInterrupt();
 
 	/* Initialise the critical nesting count ready for the first task. */
 	uxCriticalNesting = 0;
@@ -370,7 +372,7 @@ uint32_t ulPreviousMask;
  * Setup the systick timer to generate the tick interrupts at the required
  * frequency.
  */
-void prvSetupTimerInterrupt( void )
+__attribute__(( weak )) void vPortSetupTimerInterrupt( void )
 {
 	/* Calculate the constants required to configure the tick interrupt. */
 	#if( configUSE_TICKLESS_IDLE == 1 )

FreeRTOS/Source/portable/IAR/ARM_CM0/port.c

@@ -92,9 +92,11 @@ power functionality only. */
 #endif /* configUSE_TICKLESS_IDLE */
 
 /*
- * Setup the timer to generate the tick interrupts.
+ * Setup the timer to generate the tick interrupts.  The implementation in this
+ * file is weak to allow application writers to change the timer used to
+ * generate the tick interrupt.
  */
-static void prvSetupTimerInterrupt( void );
+void vPortSetupTimerInterrupt( void );
 
 /*
  * Exception handlers.
@@ -159,7 +161,7 @@ BaseType_t xPortStartScheduler( void )
 
 	/* Start the timer that generates the tick ISR.  Interrupts are disabled
 	here already. */
-	prvSetupTimerInterrupt();
+	vPortSetupTimerInterrupt();
 
 	/* Initialise the critical nesting count ready for the first task. */
 	uxCriticalNesting = 0;
@@ -233,7 +235,7 @@ uint32_t ulPreviousMask;
  * Setup the systick timer to generate the tick interrupts at the required
  * frequency.
  */
-static void prvSetupTimerInterrupt( void )
+__weak void vPortSetupTimerInterrupt( void )
 {
 	/* Calculate the constants required to configure the tick interrupt. */
 	#if( configUSE_TICKLESS_IDLE == 1 )

FreeRTOS/Source/portable/RVDS/ARM_CM0/port.c

@@ -64,6 +64,15 @@
 /* Constants used with memory barrier intrinsics. */
 #define portSY_FULL_READ_WRITE		( 15 )
 
+/* Legacy macro for backward compatibility only.  This macro used to be used to
+replace the function that configures the clock used to generate the tick
+interrupt (prvSetupTimerInterrupt()), but now the function is declared weak so
+the application writer can override it by simply defining a function of the
+same name (vApplicationSetupTickInterrupt()). */
+#ifndef configOVERRIDE_DEFAULT_TICK_CONFIGURATION
+	#define configOVERRIDE_DEFAULT_TICK_CONFIGURATION 0
+#endif
+
 /* Each task maintains its own interrupt status in the critical nesting
 variable. */
 static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
@@ -87,9 +96,11 @@ static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
 #endif /* configUSE_TICKLESS_IDLE */
 
 /*
- * Setup the timer to generate the tick interrupts.
+ * Setup the timer to generate the tick interrupts.  The implementation in this
+ * file is weak to allow application writers to change the timer used to
+ * generate the tick interrupt.
  */
-static void prvSetupTimerInterrupt( void );
+void vPortSetupTimerInterrupt( void );
 
 /*
  * Exception handlers.
@@ -192,7 +203,7 @@ BaseType_t xPortStartScheduler( void )
 
 	/* Start the timer that generates the tick ISR.  Interrupts are disabled
 	here already. */
-	prvSetupTimerInterrupt();
+	vPortSetupTimerInterrupt();
 
 	/* Initialise the critical nesting count ready for the first task. */
 	uxCriticalNesting = 0;
@@ -327,8 +338,10 @@ uint32_t ulPreviousMask;
  * Setup the systick timer to generate the tick interrupts at the required
  * frequency.
  */
-void prvSetupTimerInterrupt( void )
-{
+#if( configOVERRIDE_DEFAULT_TICK_CONFIGURATION == 0 )
+
+	__weak void vPortSetupTimerInterrupt( void )
+	{
 		/* Calculate the constants required to configure the tick interrupt. */
 		#if( configUSE_TICKLESS_IDLE == 1 )
 			ulTimerCountsForOneTick = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ );
@@ -343,7 +356,9 @@ void prvSetupTimerInterrupt( void )
 		/* Configure SysTick to interrupt at the requested rate. */
 		portNVIC_SYSTICK_LOAD_REG = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
 		portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
-}
+	}
+
+#endif /* configOVERRIDE_DEFAULT_TICK_CONFIGURATION */
 /*-----------------------------------------------------------*/
 
 #if( configUSE_TICKLESS_IDLE == 1 )

FreeRTOS/Source/portable/RVDS/ARM_CM3/port.c

@@ -51,11 +51,11 @@
 	#define portNVIC_SYSTICK_CLK_BIT	( 0 )
 #endif
 
-/* The __weak attribute does not work as you might expect with the Keil tools
-so the configOVERRIDE_DEFAULT_TICK_CONFIGURATION constant must be set to 1 if
-the application writer wants to provide their own implementation of
-vPortSetupTimerInterrupt().  Ensure configOVERRIDE_DEFAULT_TICK_CONFIGURATION
-is defined. */
+/* Legacy macro for backward compatibility only.  This macro used to be used to
+replace the function that configures the clock used to generate the tick
+interrupt (prvSetupTimerInterrupt()), but now the function is declared weak so
+the application writer can override it by simply defining a function of the
+same name (vApplicationSetupTickInterrupt()). */
 #ifndef configOVERRIDE_DEFAULT_TICK_CONFIGURATION
 	#define configOVERRIDE_DEFAULT_TICK_CONFIGURATION 0
 #endif

FreeRTOS/Source/portable/RVDS/ARM_CM4F/port.c

@@ -51,11 +51,11 @@
 	#define portNVIC_SYSTICK_CLK_BIT	( 0 )
 #endif
 
-/* The __weak attribute does not work as you might expect with the Keil tools
-so the configOVERRIDE_DEFAULT_TICK_CONFIGURATION constant must be set to 1 if
-the application writer wants to provide their own implementation of
-vPortSetupTimerInterrupt().  Ensure configOVERRIDE_DEFAULT_TICK_CONFIGURATION
-is defined. */
+/* Legacy macro for backward compatibility only.  This macro used to be used to
+replace the function that configures the clock used to generate the tick
+interrupt (prvSetupTimerInterrupt()), but now the function is declared weak so
+the application writer can override it by simply defining a function of the
+same name (vApplicationSetupTickInterrupt()). */
 #ifndef configOVERRIDE_DEFAULT_TICK_CONFIGURATION
 	#define configOVERRIDE_DEFAULT_TICK_CONFIGURATION 0
 #endif

FreeRTOS/Source/portable/RVDS/ARM_CM7/r0p1/port.c

@@ -679,7 +679,7 @@ void xPortSysTickHandler( void )
  */
 #if( configOVERRIDE_DEFAULT_TICK_CONFIGURATION == 0 )
 
-	void vPortSetupTimerInterrupt( void )
+	__weak void vPortSetupTimerInterrupt( void )
 	{
 		/* Calculate the constants required to configure the tick interrupt. */
 		#if( configUSE_TICKLESS_IDLE == 1 )