alif/mpu: Add function to set read-only bit on MRAM MPU region.

To allow writing to MRAM region.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

ports/alif/mpu.c

@@ -25,6 +25,7 @@
  */
 
 #include "py/mpconfig.h"
+#include "irq.h"
 #include "mpu.h"
 #include ALIF_CMSIS_H
 
@@ -76,3 +77,13 @@ void MPU_Load_Regions(void) {
     // Load the MPU regions from the table.
     ARM_MPU_Load(0, mpu_table, sizeof(mpu_table) / sizeof(ARM_MPU_Region_t));
 }
+
+void mpu_config_mram(bool read_only) {
+    uintptr_t atomic = disable_irq();
+    ARM_MPU_Disable();
+    MPU->RNR = MP_MPU_REGION_MRAM;
+    MPU->RBAR = ARM_MPU_RBAR(MRAM_BASE, ARM_MPU_SH_NON, read_only, 1, 0);
+    MPU->RLAR = ARM_MPU_RLAR(MRAM_BASE + MRAM_SIZE - 1, MP_MPU_ATTR_NORMAL_WT_RA);
+    ARM_MPU_Enable(MPU_CTRL_PRIVDEFENA_Msk | MPU_CTRL_HFNMIENA_Msk);
+    enable_irq(atomic);
+}

ports/alif/mpu.h

@@ -24,6 +24,8 @@
  * THE SOFTWARE.
  */
 
+#include <stdbool.h>
+
 #define MP_MPU_ATTR_NORMAL_WT_RA_TRANSIENT  (0)
 #define MP_MPU_ATTR_DEVICE_nGnRE            (1)
 #define MP_MPU_ATTR_NORMAL_WB_RA_WA         (2)
@@ -37,3 +39,5 @@
 #define MP_MPU_REGION_OSPI_REGISTERS        (4)
 #define MP_MPU_REGION_OSPI0_XIP             (5)
 #define MP_MPU_REGION_OPENAMP               (6)
+
+void mpu_config_mram(bool read_only);