[PATCH 1/5] x86: provide mb() macro

[Philip Oberfichtner]

Implement memory barrier using mfence. Linux does it equivalently [1].

"The MFENCE instruction establishes a memory fence for both loads and
stores" [2].

[1] linux/arch/x86/include/asm/barrier.h
[2] Intel® 64 and IA-32 Architectures Software Developer’s Manual

Signed-off-by: Philip Oberfichtner <pro at denx.de>
---
 arch/x86/include/asm/io.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 5efb2e1b21..936ad6f588 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -244,6 +244,7 @@ static inline void sync(void)
  * have some advantages to use them instead of the simple one here.
  */
 #define dmb()		__asm__ __volatile__ ("" : : : "memory")
+#define mb()		__asm__ __volatile__ ("mfence" : : : "memory")
 #define __iormb()	dmb()
 #define __iowmb()	dmb()
 
-- 
2.39.2