[PATCH 4.16 006/279] MIPS: io: Prevent compiler reordering writeX()

[Greg Kroah-Hartman]

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sinan Kaya <okaya@xxxxxxxxxxxxxx>

[ Upstream commit f6b7aeee8f167409195fbf1364d02988fecad1d0 ]

writeX() has strong ordering semantics with respect to memory updates.
In the absence of a write barrier or a compiler barrier, the compiler
can reorder register and memory update instructions. This breaks the
writeX() API.

Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/18997/
[jhogan@xxxxxxxxxx: Tidy commit message]
Signed-off-by: James Hogan <jhogan@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/mips/include/asm/io.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -307,7 +307,7 @@ static inline void iounmap(const volatil
 #if defined(CONFIG_CPU_CAVIUM_OCTEON) || defined(CONFIG_LOONGSON3_ENHANCEMENT)
 #define war_io_reorder_wmb()		wmb()
 #else
-#define war_io_reorder_wmb()		do { } while (0)
+#define war_io_reorder_wmb()		barrier()
 #endif
 
 #define __BUILD_MEMORY_SINGLE(pfx, bwlq, type, irq)			\