Add workaround to XMC4000 silicon bug to Tasking Cortex-M4F port layer.

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

@@ -88,6 +88,15 @@
 #define portINITIAL_XPSR			( 0x01000000 )
 #define portINITIAL_EXEC_RETURN		( 0xfffffffd )
 
+/* Let the user override the pre-loading of the initial LR with the address of
+prvTaskExitError() in case is messes up unwinding of the stack in the
+debugger. */
+#ifdef configTASK_RETURN_ADDRESS
+	#define portTASK_RETURN_ADDRESS	configTASK_RETURN_ADDRESS
+#else
+	#define portTASK_RETURN_ADDRESS	prvTaskExitError
+#endif
+
 /* The priority used by the kernel is assigned to a variable to make access
 from inline assembler easier. */
 const unsigned long ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;
@@ -112,6 +121,11 @@ void SysTick_Handler( void );
 extern void vPortEnableVFP( void );
 extern void vPortStartFirstTask( void );
 
+/*
+ * Used to catch tasks that attempt to return from their implementing function.
+ */
+static void prvTaskExitError( void );
+
 /* This exists purely to allow the const to be used from within the
 port_asm.asm assembly file. */
 const unsigned long ulMaxSyscallInterruptPriorityConst = configMAX_SYSCALL_INTERRUPT_PRIORITY;
@@ -134,7 +148,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
-	*pxTopOfStack = 0;	/* LR */
+	*pxTopOfStack = ( portSTACK_TYPE ) portTASK_RETURN_ADDRESS;	/* LR */
 
 	/* Save code space by skipping register initialisation. */
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
@@ -151,6 +165,20 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 }
 /*-----------------------------------------------------------*/
 
+static void prvTaskExitError( void )
+{
+	/* A function that implements a task must not exit or attempt to return to
+	its caller as there is nothing to return to.  If a task wants to exit it 
+	should instead call vTaskDelete( NULL ).
+	
+	Artificially force an assert() to be triggered if configASSERT() is 
+	defined, then stop here so application writers can catch the error. */
+	configASSERT( ulCriticalNesting == ~0UL );
+	portDISABLE_INTERRUPTS();	
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
 /*
  * See header file for description.
  */

FreeRTOS/Source/portable/Tasking/ARM_CM4F/port_asm.asm

@@ -51,21 +51,26 @@
 ;    licensing and training services.
 ;*/
 
+
 	.extern pxCurrentTCB
 	.extern vTaskSwitchContext
 	.extern ulMaxSyscallInterruptPriorityConst
 
-	.global PendSV_Handler
+	.global _vector_14
+	.global _lc_ref__vector_pp_14
 	.global SVC_Handler
 	.global vPortStartFirstTask
 	.global vPortEnableVFP
+	.global ulPortSetInterruptMask
+	.global vPortClearInterruptMask
 	
 ;-----------------------------------------------------------
 
 	.section .text
 	.thumb
 	.align 4
-PendSV_Handler: .type func
+_vector_14: .type func
+
 	mrs r0, psp
 
 	;Get the location of the current TCB.
@@ -106,7 +111,60 @@ PendSV_Handler: .type func
 	msr psp, r0
 	bx r14
 
-	.size	PendSV_Handler, $-PendSV_Handler
+	.size	_vector_14, $-_vector_14
+	.endsec
+
+;-----------------------------------------------------------
+
+; This function is an XMC4000 silicon errata workaround.  It will get used when
+; the SILICON_BUG_PMC_CM_001 linker macro is defined.
+	.section .text
+	.thumb
+	.align 4
+_lc_ref__vector_pp_14: .type func
+
+	mrs r0, psp
+
+	;Get the location of the current TCB.
+	ldr.w	r3, =pxCurrentTCB
+	ldr	r2, [r3]
+
+	;Is the task using the FPU context?  If so, push high vfp registers.
+	tst r14, #0x10
+	it eq
+	vstmdbeq r0!, {s16-s31}
+
+	;Save the core registers.
+	stmdb r0!, {r4-r11, r14}
+
+	;Save the new top of stack into the first member of the TCB.
+	str r0, [r2]
+
+	stmdb sp!, {r3, r14}
+	ldr.w r0, =ulMaxSyscallInterruptPriorityConst
+	msr basepri, r0
+	bl vTaskSwitchContext
+	mov r0, #0
+	msr basepri, r0
+	ldmia sp!, {r3, r14}
+
+	;The first item in pxCurrentTCB is the task top of stack.
+	ldr r1, [r3]
+	ldr r0, [r1]
+
+	;Pop the core registers.
+	ldmia r0!, {r4-r11, r14}
+
+	;Is the task using the FPU context?  If so, pop the high vfp registers too.
+	tst r14, #0x10
+	it eq
+	vldmiaeq r0!, {s16-s31}
+
+	msr psp, r0
+	push { lr }
+	pop { pc } ; XMC4000 specific errata workaround.  Do not used "bx lr" here.
+
+	.size	_lc_ref__vector_pp_14, $-_lc_ref__vector_pp_14
 	.endsec
 
 ;-----------------------------------------------------------
@@ -163,6 +221,31 @@ vPortEnableVFP .type func
 	.size	vPortEnableVFP, $-vPortEnableVFP
 	.endsec
 
+;-----------------------------------------------------------
+
+	.section .text
+	.thumb
+	.align 4
+ulPortSetInterruptMask:
+	mrs r0, basepri
+	ldr.w r1, =ulMaxSyscallInterruptPriorityConst
+	msr basepri, r1
+	bx r14
+	.size	ulPortSetInterruptMask, $-ulPortSetInterruptMask
+	.endsec
+
+;-----------------------------------------------------------
+
+	.section .text
+	.thumb
+	.align 4
+vPortClearInterruptMask:
+	msr basepri, r0
+	bx r14
+	.size	vPortClearInterruptMask, $-vPortClearInterruptMask
+	.endsec
+
+;-----------------------------------------------------------
 
 	.end
 	

FreeRTOS/Source/portable/Tasking/ARM_CM4F/portmacro.h

@@ -131,10 +131,10 @@ extern void vPortYield( void );
  */
 #define portCLEAR_INTERRUPT_MASK() __set_BASEPRI( 0 )
 
-/* FAQ:  Setting BASEPRI to 0 is not a bug.  Please see
+extern unsigned long ulPortSetInterruptMask( void );
-http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html before disagreeing. */
+extern void vPortClearInterruptMask( unsigned long ulNewMask );
-#define portSET_INTERRUPT_MASK_FROM_ISR()		0;portSET_INTERRUPT_MASK()
+#define portSET_INTERRUPT_MASK_FROM_ISR()		ulPortSetInterruptMask()
-#define portCLEAR_INTERRUPT_MASK_FROM_ISR(x)	portCLEAR_INTERRUPT_MASK();(void)x
+#define portCLEAR_INTERRUPT_MASK_FROM_ISR(x)	vPortClearInterruptMask( x )
 
 
 extern void vPortEnterCritical( void );