[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>

diff --git a/include/asm-powerpc/io.h b/include/asm-powerpc/io.h
index e0062d7..8918948 100644 (file)
--- 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")