Merge pull request #11 from forg0ne/CM7-basepri_errata

Fix for Cortex-M7 basepri errata.

Author: forg0ne

Ports/ARM-Cortex-M/ARMv7-M/ARM/os_cpu_a.asm

@@ -361,7 +361,11 @@ OS_CPU_PendSVHandler
     MSR     PSP, R0                                             ; Load PSP with new process SP
 
     MOV32   R2, #0                                              ; Restore BASEPRI priority level to 0
+    CPSID   I
     MSR     BASEPRI, R2
+    DSB
+    ISB
+    CPSIE   I
     BX      LR                                                  ; Exception return will restore remaining context
 
     ALIGN                                                       ; Removes warning[A1581W]: added <no_padbytes> of padding at <address>

Ports/ARM-Cortex-M/ARMv7-M/CCS/os_cpu_a.asm

@@ -382,7 +382,11 @@ OS_CPU_PendSVHandler:
     MSR     PSP, R0                                             ; Load PSP with new process SP
 
     MOV     R2, #0                                              ; Restore BASEPRI priority level to 0
+    CPSID   I
     MSR     BASEPRI, R2
+    DSB
+    ISB
+    CPSIE   I
     BX      LR                                                  ; Exception return will restore remaining context
     .endasmfunc
 

Ports/ARM-Cortex-M/ARMv7-M/GNU/os_cpu_a.S

@@ -379,7 +379,11 @@ OS_CPU_PendSVHandler:
     MSR     PSP, R0                                             @ Load PSP with new process SP
 
     MOV     R2, #0                                              @ Restore BASEPRI priority level to 0
+    CPSID   I
     MSR     BASEPRI, R2
+    DSB
+    ISB
+    CPSIE   I
     BX      LR                                                  @ Exception return will restore remaining context
 
 .end

Ports/ARM-Cortex-M/ARMv7-M/IAR/os_cpu_a.asm

@@ -355,7 +355,11 @@ OS_CPU_PendSVHandler
     MSR     PSP, R0                                             ; Load PSP with new process SP
 
     MOV32   R2, #0                                              ; Restore BASEPRI priority level to 0
+    CPSID   I
     MSR     BASEPRI, R2
+    DSB
+    ISB
+    CPSIE   I
     BX      LR                                                  ; Exception return will restore remaining context
 
     END