[PATCH v2 1/3] ARC: IO: add volatile to accessors
Eugeniy Paltsev
Eugeniy.Paltsev at synopsys.com
Mon Mar 30 21:44:43 CEST 2020
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 at 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)
--
2.21.1
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