[PATCH 4.14 005/189] MIPS: io: Prevent compiler reordering writeX()

Greg Kroah-Hartman
2018-06-18T08:29:53Z

From: Sinan Kaya <okaya@codeaurora.org>

[ 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@codeaurora.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/18997/
[jhogan@kernel.org: Tidy commit message]
Signed-off-by: James Hogan <jhogan@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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) \