[POWERPC] Add "memory" clobber to MMIO accessors

Gcc might re-order MMIO accessors vs. surrounding consistent
memory accesses, which is a "bad thing", and could break drivers.
This fixes it by adding a "memory" clobber to the MMIO accessors,
which should prevent gcc from doing that reordering.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/include/asm-powerpc/io.h b/include/asm-powerpc/io.h
index e0062d73db1c..89189488e286 100644
--- a/include/asm-powerpc/io.h
+++ b/include/asm-powerpc/io.h
@@ -100,7 +100,7 @@ static inline type name(const volatile type __iomem *addr)		\
 {                                                                       \
         type ret;                                                       \
         __asm__ __volatile__("sync;" insn ";twi 0,%0,0;isync"           \
-                : "=r" (ret) : "r" (addr), "m" (*addr));                \
+                : "=r" (ret) : "r" (addr), "m" (*addr) : "memory");     \
         return ret;                                                     \
 }
 
@@ -108,8 +108,8 @@ static inline type name(const volatile type __iomem *addr)		\
 static inline void name(volatile type __iomem *addr, type val)          \
 {                                                                       \
         __asm__ __volatile__("sync;" insn                               \
-                : "=m" (*addr) : "r" (val), "r" (addr));                \
-        IO_SET_SYNC_FLAG();                                     \
+                : "=m" (*addr) : "r" (val), "r" (addr) : "memory");     \
+        IO_SET_SYNC_FLAG();                                             \
 }
 
 
@@ -333,7 +333,8 @@ static inline unsigned int name(unsigned int port)	\
                 "       .long   3b,5b\n"                \
                 ".previous"                             \
                 : "=&r" (x)                             \
-                : "r" (port + _IO_BASE));               \
+                : "r" (port + _IO_BASE)                 \
+                : "memory");                            \
         return x;                                       \
 }
 
@@ -350,7 +351,8 @@ static inline void name(unsigned int val, unsigned int port) \
                 "       .long   0b,2b\n"                \
                 "       .long   1b,2b\n"                \
                 ".previous"                             \
-                : : "r" (val), "r" (port + _IO_BASE));  \
+                : : "r" (val), "r" (port + _IO_BASE)    \
+                : "memory");                            \
 }
 
 __do_in_asm(_rec_inb, "lbzx")