Add v8m MPU

Add a driver for the v8m MPU.

hal/mpu/mbed_mpu_v8m.c

@@ -0,0 +1,125 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "hal/mpu_api.h"
+#include "cmsis.h"
+
+#if ((__ARM_ARCH_8M_BASE__ == 1U) || (__ARM_ARCH_8M_MAIN__ == 1U)) && \
+    defined (__MPU_PRESENT) && (__MPU_PRESENT == 1U)
+
+#if !DEVICE_MPU
+#error "Device has v8m MPU but it is not enabled. Add 'MPU' to device_has in targets.json"
+#endif
+
+void mbed_mpu_init()
+{
+    mbed_mpu_enable_ram_xn(false);
+}
+
+void mbed_mpu_free()
+{
+    mbed_mpu_enable_ram_xn(false);
+}
+
+void mbed_mpu_enable_ram_xn(bool enable)
+{
+    // Flush memory writes before configuring the MPU.
+    __DSB();
+
+    const uint32_t regions = (MPU->TYPE & MPU_TYPE_DREGION_Msk) >> MPU_TYPE_DREGION_Pos;
+
+    // Disable the MCU
+    MPU->CTRL = 0;
+
+    // Reset all mapping
+    for (uint32_t i = 0; i < regions; i++) {
+        ARM_MPU_ClrRegionEx(MPU, i);
+    }
+
+    if (!enable) {
+        return;
+    }
+
+    /*
+     * ARMv8m memory map:
+     *
+     * Start        End            Name            Executable by default    Default cache       Mbed MPU protection
+     * 0x00000000 - 0x1FFFFFFF     Code            Yes                      WT, WA
+     * 0x20000000 - 0x3FFFFFFF     SRAM            Yes                      WB, WA, RA          Execute disabled
+     * 0x40000000 - 0x5FFFFFFF     Peripheral      No
+     * 0x60000000 - 0x7FFFFFFF     RAM             Yes                      WB, WA, RA          Execute disabled
+     * 0x80000000 - 0x9FFFFFFF     RAM             Yes                      WT, RA              Execute disabled
+     * 0xA0000000 - 0xBFFFFFFF     Device          No
+     * 0xC0000000 - 0xDFFFFFFF     Device          No
+     * 0xE0000000 - 0xFFFFFFFF     System          No
+     */
+
+    if (regions >= 3) {
+        uint32_t region;
+        uint8_t outer;
+        uint8_t inner;
+
+        region = 0;
+        MPU->RNR = region;
+        outer = 0xF;    // Write-Back, Non-transient, Read-allocate, Write-allocate
+        outer = 0xF;    // Write-Back, Non-transient, Read-allocate, Write-allocate
+        ARM_MPU_SetMemAttrEx(MPU, region, (outer << 4) | (inner << 0));
+        MPU->RBAR = (0x20000000 & MPU_RBAR_BASE_Msk) |      // Start address is 0x20000000
+                       (0 << MPU_RBAR_SH_Pos) |             // Not shareable
+                       (1 << MPU_RBAR_AP_Pos) |             // RW allowed by all privilege levels
+                       (1 << MPU_RBAR_XN_Pos);              // Execute Never enabled
+        MPU->RLAR = (0x3FFFFFFF & MPU_RLAR_LIMIT_Msk) |     // Last address is 0x3FFFFFFF
+                       (region << MPU_RLAR_AttrIndx_Pos) |  // Attribute index - configured to be the same as the region number
+                       (1 << MPU_RLAR_EN_Pos);              // Enable region
+
+        region = 1;
+        MPU->RNR = region;
+        outer = 0xF;    // Write-Back, Non-transient, Read-allocate, Write-allocate
+        outer = 0xF;    // Write-Back, Non-transient, Read-allocate, Write-allocate
+        ARM_MPU_SetMemAttrEx(MPU, region, (outer << 4) | (inner << 0));
+        MPU->RBAR = (0x60000000 & MPU_RBAR_BASE_Msk) |      // Start address is 0x60000000
+                       (0 << MPU_RBAR_SH_Pos) |             // Not shareable
+                       (1 << MPU_RBAR_AP_Pos) |             // RW allowed by all privilege levels
+                       (1 << MPU_RBAR_XN_Pos);              // Execute Never enabled
+        MPU->RLAR = (0x7FFFFFFF & MPU_RLAR_LIMIT_Msk) |     // Last address is 0x7FFFFFFF
+                       (region << MPU_RLAR_AttrIndx_Pos) |  // Attribute index - configured to be the same as the region number
+                       (1 << MPU_RLAR_EN_Pos);              // Enable region
+
+        region = 2;
+        MPU->RNR = region;
+        outer = 0xA;    // Write-Through, Non-transient, Read-allocate
+        inner = 0xA;    // Write-Through, Non-transient, Read-allocate
+        ARM_MPU_SetMemAttrEx(MPU, region, (outer << 4) | (inner << 0));
+        MPU->RBAR = (0x80000000 & MPU_RBAR_BASE_Msk) |      // Start address is 0x80000000
+                       (0 << MPU_RBAR_SH_Pos) |             // Not shareable
+                       (1 << MPU_RBAR_AP_Pos) |             // RW allowed by all privilege levels
+                       (1 << MPU_RBAR_XN_Pos);              // Execute Never enabled
+        MPU->RLAR = (0x9FFFFFFF & MPU_RLAR_LIMIT_Msk) |     // Last address is 0x9FFFFFFF
+                       (region << MPU_RLAR_AttrIndx_Pos) |  // Attribute index - configured to be the same as the region number
+                       (1 << MPU_RLAR_EN_Pos);              // Enable region
+    }
+
+    // Enable the MPU
+    MPU->CTRL =
+        (1 << MPU_CTRL_PRIVDEFENA_Pos) |            // Use the default memory map for unmapped addresses
+        (1 << MPU_CTRL_HFNMIENA_Pos) |              // Keep MPU turned on for faults
+        (1 << MPU_CTRL_ENABLE_Pos);                 // Enable MPU
+
+    // Ensure changes take effect
+    __ISB();
+    __DSB();
+}
+
+#endif