MIPS: io: Add barrier after register read in inX()

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@vger.kernel.org
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Patchwork: https://patchwork.linux-mips.org/patch/19516/
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <james.hogan@mips.com>
Cc: linux-mips@linux-mips.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: Huacai Chen <chenhuacai@gmail.com>

diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
index a7d0b83..cea8ad8 100644 (file)
--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -414,6 +414,8 @@ static inline type pfx##in##bwlq##p(unsigned long port)                     \
        __val = *__addr;                                                \
        slow;                                                           \
                                                                        \
+       /* prevent prefetching of coherent DMA data prematurely */      \
+       rmb();                                                          \
        return pfx##ioswab##bwlq(__addr, __val);                        \
 }