We must use 'volatile' in C-version read/write IO accessors implementation to avoid merging several reads (writes) into one read (write), or optimizing them out by compiler.
Fixes commit 07906b3dad15 ("ARC: Switch to generic accessors")
Signed-off-by: Eugeniy Paltsev Eugeniy.Paltsev@synopsys.com --- arch/arc/include/asm/io.h | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h index 70d050590de..1f1ae889f3a 100644 --- a/arch/arc/include/asm/io.h +++ b/arch/arc/include/asm/io.h @@ -54,15 +54,21 @@ static inline void sync(void) /* Not yet implemented */ }
-#define __arch_getb(a) (*(unsigned char *)(a)) -#define __arch_getw(a) (*(unsigned short *)(a)) -#define __arch_getl(a) (*(unsigned int *)(a)) -#define __arch_getq(a) (*(unsigned long long *)(a)) - -#define __arch_putb(v, a) (*(unsigned char *)(a) = (v)) -#define __arch_putw(v, a) (*(unsigned short *)(a) = (v)) -#define __arch_putl(v, a) (*(unsigned int *)(a) = (v)) -#define __arch_putq(v, a) (*(unsigned long long *)(a) = (v)) +/* + * We must use 'volatile' in C-version read/write IO accessors implementation + * to avoid merging several reads (writes) into one read (write), or optimizing + * them out by compiler. + */ +#define __arch_getb(a) (*(volatile u8 *)(a)) +#define __arch_getw(a) (*(volatile u16 *)(a)) +#define __arch_getl(a) (*(volatile u32 *)(a)) +#define __arch_getq(a) (*(volatile u64 *)(a)) + +#define __arch_putb(v, a) (*(volatile u8 *)(a) = (v)) +#define __arch_putw(v, a) (*(volatile u16 *)(a) = (v)) +#define __arch_putl(v, a) (*(volatile u32 *)(a) = (v)) +#define __arch_putq(v, a) (*(volatile u64 *)(a) = (v)) +
#define __raw_writeb(v, a) __arch_putb(v, a) #define __raw_writew(v, a) __arch_putw(v, a)