diff --git a/arch/arm/src/armv7-m/mpu.h b/arch/arm/src/armv7-m/mpu.h
index 2e3770ffb67..310c21a9091 100644
--- a/arch/arm/src/armv7-m/mpu.h
+++ b/arch/arm/src/armv7-m/mpu.h
@@ -1,4 +1,4 @@
-/************************************************************************************
+/*****************************************************************************
  * arch/arm/src/armv7-m/mpu.h
  *
  *   Copyright (C) 2011, 2013 Gregory Nutt. All rights reserved.
@@ -31,14 +31,14 @@
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  *
- ************************************************************************************/
+ ****************************************************************************/
 
 #ifndef __ARCH_ARM_SRC_ARMV7M_MPU_H
 #define __ARCH_ARM_SRC_ARMV7M_MPU_H
 
-/************************************************************************************
+/****************************************************************************
  * Included Files
- ************************************************************************************/
+ ****************************************************************************/
 
 #include <nuttx/config.h>
 
@@ -46,14 +46,15 @@
 #  include <sys/types.h>
 #  include <stdint.h>
 #  include <stdbool.h>
+#  include <assert.h>
 #  include <debug.h>
 
 #  include "up_arch.h"
 #endif
 
-/************************************************************************************
+/****************************************************************************
  * Pre-processor Definitions
- ************************************************************************************/
+ ****************************************************************************/
 
 /* MPU Register Addresses */
 
@@ -86,14 +87,16 @@
 
 /* MPU Region Number Register Bit Definitions */
 
-#if CONFIG_ARM_MPU_NREGIONS <= 8
-#  define MPU_RNR_MASK            (0x00000007)
-#elif CONFIG_ARM_MPU_NREGIONS <= 16
-#  define MPU_RNR_MASK            (0x0000000f)
-#elif CONFIG_ARM_MPU_NREGIONS <= 32
-#  define MPU_RNR_MASK            (0x0000001f)
-#else
-#  error "FIXME: Unsupported number of MPU regions"
+#if defined(CONFIG_ARM_MPU_NREGIONS)
+#  if CONFIG_ARM_MPU_NREGIONS <= 8
+#    define MPU_RNR_MASK            (0x00000007)
+#  elif CONFIG_ARM_MPU_NREGIONS <= 16
+#    define MPU_RNR_MASK            (0x0000000f)
+#  elif CONFIG_ARM_MPU_NREGIONS <= 32
+#    define MPU_RNR_MASK            (0x0000001f)
+#  else
+#    error "FIXME: Unsupported number of MPU regions"
+#  endif
 #endif
 
 /* MPU Region Base Address Register Bit Definitions */
@@ -136,9 +139,9 @@
 #    define MPU_RASR_AP_RORO    (6 << MPU_RASR_AP_SHIFT) /* P:RO   U:RO   */
 #  define MPU_RASR_XN           (1 << 28) /* Bit 28: Instruction access disable */
 
-/************************************************************************************
+/****************************************************************************
  * Public Function Prototypes
- ************************************************************************************/
+ ****************************************************************************/
 
 #ifndef __ASSEMBLY__
 #undef EXTERN
@@ -202,9 +205,9 @@ uint8_t mpu_log2regionfloor(size_t size);
 
 uint32_t mpu_subregion(uintptr_t base, size_t size, uint8_t l2size);
 
-/************************************************************************************
+/****************************************************************************
  * Inline Functions
- ************************************************************************************/
+ ****************************************************************************/
 
 /****************************************************************************
  * Name: mpu_showtype
@@ -255,6 +258,7 @@ static inline void mpu_control(bool enable, bool hfnmiena, bool privdefena)
   putreg32(regval, MPU_CTRL);
 }
 
+
 /****************************************************************************
  * Name: mpu_priv_stronglyordered
  *
diff --git a/arch/arm/src/armv7-r/mpu.h b/arch/arm/src/armv7-r/mpu.h
index 4cd962b9f73..67aeb2e94a2 100644
--- a/arch/arm/src/armv7-r/mpu.h
+++ b/arch/arm/src/armv7-r/mpu.h
@@ -1,4 +1,4 @@
-/************************************************************************************
+/****************************************************************************
  * arch/arm/src/armv7-r/mpu.h
  *
  *   Copyright (C) 2015 Gregory Nutt. All rights reserved.
@@ -31,14 +31,14 @@
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  *
- ************************************************************************************/
+ ****************************************************************************/
 
 #ifndef __ARCH_ARM_SRC_ARMV7R_MPU_H
 #define __ARCH_ARM_SRC_ARMV7R_MPU_H
 
-/************************************************************************************
+/****************************************************************************
  * Included Files
- ************************************************************************************/
+ ****************************************************************************/
 
 #include <nuttx/config.h>
 
@@ -52,9 +52,9 @@
 #  include "cp15.h"
 #endif
 
-/************************************************************************************
+/****************************************************************************
  * Pre-processor Definitions
- ************************************************************************************/
+ ****************************************************************************/
 
 /* MPU Type Register Bit Definitions */
 
@@ -106,19 +106,21 @@
 
 /* MPU Region Number Register */
 
-#if CONFIG_ARM_MPU_NREGIONS <= 8
-#  define MPU_RGNR_MASK          (0x00000007)
-#elif CONFIG_ARM_MPU_NREGIONS <= 16
-#  define MPU_RGNR_MASK          (0x0000000f)
-#elif CONFIG_ARM_MPU_NREGIONS <= 32
-#  define MPU_RGNR_MASK          (0x0000001f)
-#else
+#if defined(CONFIG_ARM_MPU_NREGIONS)
+#  if CONFIG_ARM_MPU_NREGIONS <= 8
+#    define MPU_RGNR_MASK        (0x00000007)
+#  elif CONFIG_ARM_MPU_NREGIONS <= 16
+#    define MPU_RGNR_MASK        (0x0000000f)
+#  elif CONFIG_ARM_MPU_NREGIONS <= 32
+#    define MPU_RGNR_MASK        (0x0000001f)
+#  else
 #  error "FIXME: Unsupported number of MPU regions"
+#  endif
 #endif
 
-/************************************************************************************
+/****************************************************************************
  * Public Function Prototypes
- ************************************************************************************/
+ ****************************************************************************/
 
 #ifndef __ASSEMBLY__
 #undef EXTERN
@@ -182,9 +184,9 @@ uint8_t mpu_log2regionfloor(size_t size);
 
 uint32_t mpu_subregion(uintptr_t base, size_t size, uint8_t l2size);
 
-/************************************************************************************
+/****************************************************************************
  * Inline Functions
- ************************************************************************************/
+ ****************************************************************************/
 
 /****************************************************************************
  * Name: mpu_get_mpuir