[PATCH v4 3/5] io: define stronger ordering for the default writeX() implementation

Sinan Kaya
2018-04-05T13:10:05Z

The default implementation of mapping writeX() to __raw_writeX() is wrong.
writeX() has stronger ordering semantics. Compiler is allowed to reorder
memory writes against __raw_writeX().

Use the previously defined __io_aw() and __io_bw() macros to harden
code generation according to architecture support.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
include/asm-generic/io.h | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index d27e8af..964725e 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -208,7 +208,9 @@ static inline u64 readq(const volatile void __iomem *addr)
#define writeb writeb
static inline void writeb(u8 value, volatile void __iomem *addr)
{
+ __io_bw();
__raw_writeb(value, addr);
+ __io_aw();
}
#endif

@@ -216,7 +218,9 @@ static inline void writeb(u8 value, volatile void __iomem *addr)
#define writew writew
static inline void writew(u16 value, volatile void __iomem *addr)
{
+ __io_bw();
__raw_writew(cpu_to_le16(value), addr);
+ __io_aw();
}
#endif

@@ -224,7 +228,9 @@ static inline void writew(u16 value, volatile void __iomem *addr)
#define writel writel
static inline void writel(u32 value, volatile void __iomem *addr)
{
+ __io_bw();
__raw_writel(__cpu_to_le32(value), addr);
+ __io_aw();
}
#endif

@@ -233,7 +239,9 @@ static inline void writel(u32 value, volatile void __iomem *addr)
#define writeq writeq
static inline void writeq(u64 value, volatile void __iomem *addr)
{
+ __io_bw();
__raw_writeq(__cpu_to_le64(value), addr);
+ __io_aw();
}
#endif
#endif /* CONFIG_64BIT */
--
2.7.4