Xtensa: fix the coproc_area incorrect issue (#117)

* Xtensa: fix the coproc_area incorrect issue

foss-xtensa/amazon-freertos#2 mentioned a issue:
1.
In function pxPortInitialiseStack(StackType_t *pxTopOfStack....)
p = (uint32_t *)(((uint32_t) pxTopOfStack - XT_CP_SIZE) & ~0xf);

In function prvInitialiseNewTask (file: task.c)
pxTopOfStack = (pxStack + (ulStackDepth - 1)) & (~portBYTE_ALIGNMENT_MASK)

So the co-processor area is at
p = (uint32_t *)(((uint32_t)((pxStack + (ulStackDepth - 1)) & (~portBYTE_ALIGNMENT_MASK)) - XT_CP_SIZE) & ~0xf);

2.
In function vPortStoreTaskMPUSettings( .... , StackType_t pxBottomOfStack ...)
xMPUSettings->coproc_area = (StackType_t)((((uint32_t)(pxBottomOfStack + usStackDepth - 1)) - XT_CP_SIZE) & ~0xf);

pxBottomOfStack = pxStack

=> xMPUSettings->coproc_area = (StackType_t*)((((uint32_t)(pxStack+ ulStackDepth - 1)) - XT_CP_SIZE ) & ~0xf);

The p is coproc_area that should be equal to xMPUSettings->coproc_area.

For example, assume pxStack is 0xa0000000, ulStackDepth is 0x2000,
portBYTE_ALIGNMENT_MASK is 0x7f, XT_CP_SIZE is 0x100.

The p = (uint32_t)(((uint32_t)((pxStack + (ulStackDepth - 1)) & (~portBYTE_ALIGNMENT_MASK)) - XT_CP_SIZE) & ~0xf)
      = 0xa0001e80
The xMPUSettings->coproc_area = (StackType_t)((((uint32_t)(pxStack+ usStackDepth - 1)) - XT_CP_SIZE ) & ~0xf)
                              = 0xa0001ef0
Obviously, the p is not equal to the xMPUSettings->coproc_area, which will cause context switching error.

Signed-off-by: magicse7en <magicse7en@outlook.com>

* Update port.c

Co-authored-by: Carl Lundin <53273776+lundinc2@users.noreply.github.com>

Author: magicse7en

portable/ThirdParty/XCC/Xtensa/port.c

@@ -212,16 +212,19 @@ BaseType_t xPortSysTickHandler( void )
  * Used to set coprocessor area in stack. Current hack is to reuse MPU pointer for coprocessor area.
  */
 #if portUSING_MPU_WRAPPERS
-void vPortStoreTaskMPUSettings( xMPU_SETTINGS *xMPUSettings, const struct xMEMORY_REGION * const xRegions, StackType_t *pxBottomOfStack, uint32_t ulStackDepth )
+void vPortStoreTaskMPUSettings( xMPU_SETTINGS * xMPUSettings,
+                                const struct xMEMORY_REGION * const xRegions,
+                                StackType_t * pxBottomOfStack,
+                                uint32_t ulStackDepth )
 {
-	#if XCHAL_CP_NUM > 0
-	xMPUSettings->coproc_area = (StackType_t*)((((uint32_t)(pxBottomOfStack + ulStackDepth - 1)) - XT_CP_SIZE ) & ~0xf);
-
+    #if XCHAL_CP_NUM > 0
+        xMPUSettings->coproc_area = ( StackType_t * ) ( ( uint32_t ) ( pxBottomOfStack + ulStackDepth - 1 ));
+        xMPUSettings->coproc_area = ( StackType_t * ) ( ( ( portPOINTER_SIZE_TYPE ) xMPUSettings->coproc_area ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
+        xMPUSettings->coproc_area = ( Stacktype_t * ) ( ( ( uint32_t ) xMPUSettings->coproc_area - XT_CP_SIZE ) & ~0xf );
 
-	/* NOTE: we cannot initialize the coprocessor save area here because FreeRTOS is going to
+        /* NOTE: we cannot initialize the coprocessor save area here because FreeRTOS is going to
          * clear the stack area after we return. This is done in pxPortInitialiseStack().
-	 */
-	#endif
+         */
+    #endif
 }
-#endif
-
+#endif /* if portUSING_MPU_WRAPPERS */