arch: armv6-m: Introduce setintstack macro

Summary:
- This commit introduces setintstack macro which can be
  overridden for SMP with interrupt stack

Impact:
- SMP only

Testing:
- Tested with raspberrypi-pico:smp
- NOTE: more commits will be added later

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

arch/arm/src/armv6-m/arm_exception.S

@@ -44,6 +44,11 @@
 #include <nuttx/config.h>
 
 #include <arch/irq.h>
+
+#ifdef CONFIG_SMP
+#  include "chip.h"
+#endif
+
 #include "exc_return.h"
 
 /****************************************************************************
@@ -53,6 +58,26 @@
 	.globl		exception_common
 	.file		"arm_exception.S"
 
+/****************************************************************************
+ * Macro Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: setintstack
+ *
+ * Description:
+ *   Set the current stack pointer to the  "top" the interrupt stack.  Single CPU
+ *   case.  Must be provided by MCU-specific logic in the SMP case.
+ *
+ ****************************************************************************/
+
+#if !defined(CONFIG_SMP) && CONFIG_ARCH_INTERRUPTSTACK > 3
+	.macro	setintstack, tmp1, tmp2
+	ldr		\tmp1, =g_intstacktop
+	mov		sp, \tmp1
+	.endm
+#endif
+
 /****************************************************************************
  * .text
  ****************************************************************************/
@@ -142,8 +167,7 @@ exception_common:
 	 */
 
 #if CONFIG_ARCH_INTERRUPTSTACK > 3
-	ldr		r7, =g_intstacktop			/* R7=Top of the interrupt stack */
-	mov		sp, r7					/* Set the new stack point */
+	setintstack     r7, r6					/* SP = IRQ stack top */
 	push		{r1}					/* Save the MSP on the interrupt stack */
 	bl		arm_doirq				/* R0=IRQ, R1=register save area on stack */
 	pop		{r1}					/* Recover R1=main stack pointer */