Kinetis:Disable MPU when not in protected mode.

The hardware reset state of the the MPU precludes any bus
   masters other then DMA access to memory. Unfortunately
   USB and SDHC have there own DMA and will not have access to
   memory in the default reset state.

   This change disabled the MPU if present on system startup.

arch/arm/src/kinetis/Make.defs

@@ -116,6 +116,7 @@ CHIP_CSRCS += kinetis_lowputc.c kinetis_pin.c kinetis_pingpio.c
 CHIP_CSRCS += kinetis_serialinit.c kinetis_serial.c
 CHIP_CSRCS += kinetis_start.c kinetis_uid.c kinetis_wdog.c
 CHIP_CSRCS += kinetis_cfmconfig.c
+CHIP_CSRCS += kinetis_mpuinit.c
 
 # Configuration-dependent Kinetis files
 
@@ -124,7 +125,7 @@ CHIP_CSRCS += kinetis_timerisr.c
 endif
 
 ifeq ($(CONFIG_BUILD_PROTECTED),y)
-CHIP_CSRCS += kinetis_userspace.c kinetis_mpuinit.c
+CHIP_CSRCS += kinetis_userspace.c
 endif
 
 ifeq ($(CONFIG_KINETIS_GPIOIRQ),y)

arch/arm/src/kinetis/kinetis_mpuinit.c

@@ -45,6 +45,7 @@
 
 #include "mpu.h"
 #include "kinetis_mpuinit.h"
+#include "chip/kinetis_mpu.h"
 
 #if defined(CONFIG_BUILD_PROTECTED) && defined(CONFIG_ARM_MPU)
 
@@ -120,5 +121,24 @@ void kinetis_mpu_uheap(uintptr_t start, size_t size)
   mpu_user_intsram(start, size);
 }
 
+#elif defined(KINETIS_MPU)
+
+/****************************************************************************
+ * Name: kinetis_mpudisable
+ *
+ * Description:
+ *   Configure the MPU to permit All buss masters access to all resources.
+ *
+ ****************************************************************************/
+
+void kinetis_mpudisable(void)
+{
+  uint32_t regval;
+
+  regval = getreg32(KINETIS_MPU_CESR);
+  regval &= ~MPU_CESR_VLD;
+  putreg32(regval, KINETIS_MPU_CESR);
+}
+
 #endif /* CONFIG_BUILD_PROTECTED && CONFIG_ARM_MPU */
 

arch/arm/src/kinetis/kinetis_mpuinit.h

@@ -61,6 +61,18 @@ void kinetis_mpuinitialize(void);
 #  define kinetis_mpuinitialize()
 #endif
 
+/****************************************************************************
+ * Name: kinetis_mpudisable
+ *
+ * Description:
+ *   Configure the MPU to permit All buss masters access to all resources.
+ *
+ ****************************************************************************/
+
+#if !defined(CONFIG_BUILD_PROTECTED) && defined(KINETIS_MPU)
+void kinetis_mpudisable(void);
+#endif
+
 /****************************************************************************
  * Name: kinetis_mpu_uheap
  *

arch/arm/src/kinetis/kinetis_start.c

@@ -341,6 +341,12 @@ void __start(void)
 
 #ifdef CONFIG_BUILD_PROTECTED
   kinetis_userspace();
+#else
+#  ifdef KINETIS_MPU
+  /* Disable the MPU so that all master may access all buses */
+
+  kinetis_mpudisable();
+#  endif
 #endif
 
   /* Initialize other on-board resources */