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* [PATCH] arc: use little endian accesses
@ 2016-03-09 17:21 Lada Trimasova
  2016-03-10  5:05 ` Vineet Gupta
  0 siblings, 1 reply; 17+ messages in thread
From: Lada Trimasova @ 2016-03-09 17:21 UTC (permalink / raw)
  To: linux-snps-arc
  Cc: linux-kernel, linux-arch, Lada Trimasova, Alexey Brodkin, Vineet Gupta

Memory access primitives should use cpu_to_le16, cpu_to_le32, le16_to_cpu
and le32_to_cpu because it is not really guaranteed that drivers handles
any ordering themselves.
For example, serial port driver doesn't work when kernel is build for
arc big endian architecture.

Signed-off-by: Lada Trimasova <ltrimas@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
---
 arch/arc/include/asm/io.h | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h
index 694ece8..0b3d5ea 100644
--- a/arch/arc/include/asm/io.h
+++ b/arch/arc/include/asm/io.h
@@ -129,15 +129,17 @@ static inline void __raw_writel(u32 w, volatile void __iomem *addr)
 #define writel(v,c)		({ __iowmb(); writel_relaxed(v,c); })
 
 /*
- * Relaxed API for drivers which can handle any ordering themselves
+ * This are defined to perform little endian accesses
  */
 #define readb_relaxed(c)	__raw_readb(c)
-#define readw_relaxed(c)	__raw_readw(c)
-#define readl_relaxed(c)	__raw_readl(c)
+#define readw_relaxed(c) ({ u16 __r = le16_to_cpu((__force __le16) \
+					__raw_readw(c)); __r; })
+#define readl_relaxed(c) ({ u32 __r = le32_to_cpu((__force __le32) \
+					__raw_readl(c)); __r; })
 
 #define writeb_relaxed(v,c)	__raw_writeb(v,c)
-#define writew_relaxed(v,c)	__raw_writew(v,c)
-#define writel_relaxed(v,c)	__raw_writel(v,c)
+#define writew_relaxed(v,c)	__raw_writew((__force u16) cpu_to_le16(v),c)
+#define writel_relaxed(v,c)	__raw_writel((__force u32) cpu_to_le32(v),c)
 
 #include <asm-generic/io.h>
 
-- 
2.5.0

^ permalink raw reply	[flat|nested] 17+ messages in thread

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Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-03-09 17:21 [PATCH] arc: use little endian accesses Lada Trimasova
2016-03-10  5:05 ` Vineet Gupta
2016-03-10  5:19   ` Vineet Gupta
2016-03-10  5:19     ` Vineet Gupta
2016-03-10  7:44   ` Alexey Brodkin
2016-03-10  9:55     ` Vineet Gupta
2016-03-10 18:57       ` Lada Trimasova
2016-03-10 18:57         ` Lada Trimasova
2016-03-10 19:23         ` Arnd Bergmann
2016-03-11 12:44           ` Vineet Gupta
2016-03-12  4:20             ` Vineet Gupta
2016-03-12  4:20               ` Vineet Gupta
2016-03-11  5:07         ` Noam Camus
2016-03-11  5:07           ` Noam Camus
2016-03-10  7:45   ` Arnd Bergmann
2016-03-10  7:45     ` Arnd Bergmann
2016-03-11  5:18     ` Vineet Gupta

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