Rework MPU use option

Make the option positively named, and as it is a platform config
option make sure it only affects platform code.

HAL functions still remain available even if platform is told not
to use them.

hal/mpu/mbed_mpu_v7m.c

@@ -20,7 +20,7 @@
 
 #if ((__ARM_ARCH_7M__ == 1U) || (__ARM_ARCH_7EM__ == 1U) || (__ARM_ARCH_6M__ == 1U)) && \
     defined (__MPU_PRESENT) && (__MPU_PRESENT == 1U) && \
-    !defined(MBED_MPU_CUSTOM) && !MBED_CONF_PLATFORM_DISABLE_MPU
+    !defined(MBED_MPU_CUSTOM)
 
 #if !DEVICE_MPU
 #error "Device has v7m MPU but it is not enabled. Add 'MPU' to device_has in targets.json"

hal/mpu/mbed_mpu_v8m.c

@@ -20,7 +20,7 @@
 
 #if ((__ARM_ARCH_8M_BASE__ == 1U) || (__ARM_ARCH_8M_MAIN__ == 1U)) && \
     defined (__MPU_PRESENT) && (__MPU_PRESENT == 1U) && \
-    !defined(MBED_MPU_CUSTOM) && !MBED_CONF_PLATFORM_DISABLE_MPU
+    !defined(MBED_MPU_CUSTOM)
 
 #if !DEVICE_MPU
 #error "Device has v8m MPU but it is not enabled. Add 'MPU' to device_has in targets.json"

hal/mpu_api.h

@@ -26,7 +26,7 @@
 extern "C" {
 #endif
 
-#if DEVICE_MPU && !MBED_CONF_PLATFORM_DISABLE_MPU
+#if DEVICE_MPU
 
 /**
  * \defgroup hal_mpu MPU hal

platform/mbed_lib.json

@@ -129,9 +129,9 @@
             "help": "Setting this to true enables auto-reboot on a fatal error.",
             "value": false
         },
-        "disable-mpu": {
-            "help": "Disable the MPU to save rom.",
-            "value": false
+        "use-mpu": {
+            "help": "Use the MPU if available to fault execution from RAM and writes to ROM. Can be disabled to reduce image size.",
+            "value": true
         }
     },
     "target_overrides": {

platform/mbed_mpu_mgmt.c

@@ -16,12 +16,11 @@
 
 #include "platform/mbed_mpu_mgmt.h"
 #include "platform/mbed_critical.h"
-#include "platform/mbed_error.h"
 #include "platform/mbed_assert.h"
 #include "hal/mpu_api.h"
 #include <limits.h>
 
-#if DEVICE_MPU && !MBED_CONF_PLATFORM_DISABLE_MPU
+#if DEVICE_MPU && MBED_CONF_PLATFORM_USE_MPU
 
 static uint16_t mem_xn_lock;
 static uint16_t mem_wn_lock;

platform/mbed_mpu_mgmt.h

@@ -23,16 +23,17 @@
 #ifndef MBED_MPU_MGMT_H
 #define MBED_MPU_MGMT_H
 
-#include "hal/sleep_api.h"
 #include "mbed_toolchain.h"
-#include "hal/ticker_api.h"
+#include "hal/mpu_api.h"
 #include <stdbool.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#if DEVICE_MPU && !MBED_CONF_PLATFORM_DISABLE_MPU
+#if (DEVICE_MPU && MBED_CONF_PLATFORM_USE_MPU) || defined(DOXYGEN_ONLY)
+
+#define mbed_mpu_manager_init() mbed_mpu_init()
 
 /** Lock ram execute never mode off
  *
@@ -84,6 +85,8 @@ void mbed_mpu_manager_unlock_rom_write(void);
 
 #else
 
+#define mbed_mpu_manager_init() (void)0
+
 #define mbed_mpu_manager_lock_ram_execution() (void)0
 
 #define mbed_mpu_manager_unlock_ram_execution() (void)0

rtos/TARGET_CORTEX/mbed_boot.c

@@ -76,7 +76,7 @@
 #include "mbed_toolchain.h"
 #include "mbed_boot.h"
 #include "mbed_error.h"
-#include "mpu_api.h"
+#include "mbed_mpu_mgmt.h"
 
 int main(void);
 static void mbed_cpy_nvic(void);
@@ -87,7 +87,7 @@ uint32_t mbed_stack_isr_size = 0;
 
 void mbed_init(void)
 {
-    mbed_mpu_init();
+    mbed_mpu_manager_init();
     mbed_cpy_nvic();
     mbed_sdk_init();
     mbed_rtos_init();