2 files changed, 17 insertions, 7 deletions
diff --git a/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.S b/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.S
index 44160d4c32..2c859306db 100644
--- a/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.S
+++ b/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.S
@@ -1,6 +1,12 @@
 #------------------------------------------------------------------------------ 
 #
-# CpuSleep() for ARM
+# CpuSleep() for ARMv7
+#
+# ARMv6 versions was:
+#    MOV r0,#0
+#    MCR p15,0,r0,c7,c0,4   ;Wait for Interrupt instruction
+#
+# But this is a no-op on ARMv7
 #
 # Copyright (c) 2006 - 2009, Intel Corporation. All rights reserved.<BR>
 # Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
@@ -33,6 +39,5 @@ GCC_ASM_EXPORT(CpuSleep)
 #  );
 #
 ASM_PFX(CpuSleep):
-    mov r0,#0
-    mcr p15,0,r0,c7,c0,4   // Wait for Interrupt instruction
+    wfi
     bx  lr
diff --git a/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.asm b/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.asm
index 1a18eb0d07..a51e2cd9dd 100644
--- a/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.asm
+++ b/MdePkg/Library/BaseCpuLib/Arm/CpuSleep.asm
@@ -1,9 +1,15 @@
 ;------------------------------------------------------------------------------ 
 ;
-; CpuSleep() for ARM
+; CpuSleep() for ARMv7
+;
+; ARMv6 versions was:
+;    MOV r0,#0
+;    MCR p15,0,r0,c7,c0,4   ;Wait for Interrupt instruction
+;
+; But this is a no-op on ARMv7
 ;
 ; Copyright (c) 2006 - 2009, Intel Corporation. All rights reserved.<BR>
-; Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
+; Portions copyright (c) 2008 - 2011, Apple Inc. All rights reserved.<BR>
 ; This program and the accompanying materials
 ; are licensed and made available under the terms and conditions of the BSD License
 ; which accompanies this distribution.  The full text of the license may be found at
@@ -32,8 +38,7 @@
 ;  );
 ;
 CpuSleep
-    MOV r0,#0
-    MCR p15,0,r0,c7,c0,4   ;Wait for Interrupt instruction
+    WFI
     BX LR
 
   END