[PATCH 4.9 050/101] MIPS: io: Add barrier after register read in inX()

[Greg Kroah-Hartman]

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

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

From: Huacai Chen <chenhc@xxxxxxxxxx>

commit 18f3e95b90b28318ef35910d21c39908de672331 upstream.

While a barrier is present in the outX() functions before the register
write, a similar barrier is missing in the inX() functions after the
register read. This could allow memory accesses following inX() to
observe stale data.

This patch is very similar to commit a1cc7034e33d12dc1 ("MIPS: io: Add
barrier after register read in readX()"). Because war_io_reorder_wmb()
is both used by writeX() and outX(), if readX() need a barrier then so
does inX().

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
Patchwork: https://patchwork.linux-mips.org/patch/19516/
Signed-off-by: Paul Burton <paul.burton@xxxxxxxx>
Cc: James Hogan <james.hogan@xxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: Fuxin Zhang <zhangfx@xxxxxxxxxx>
Cc: Zhangjin Wu <wuzhangjin@xxxxxxxxx>
Cc: Huacai Chen <chenhuacai@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/mips/include/asm/io.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -412,6 +412,8 @@ static inline type pfx##in##bwlq##p(unsi
 	__val = *__addr;						\
 	slow;								\
 									\
+	/* prevent prefetching of coherent DMA data prematurely */	\
+	rmb();								\
 	return pfx##ioswab##bwlq(__addr, __val);			\
 }