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Commit f778cc65 authored by Lada Trimasova's avatar Lada Trimasova Committed by Vineet Gupta
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ARC: [BE] readl()/writel() to work in Big Endian CPU configuration 

read{l,w}() write{l,w}() primitives should use le{16,32}_to_cpu() and
cpu_to_le{16,32}() respectively to ensure device registers are read
correctly in Big Endian CPU configuration.

Per Arnd Bergmann
| Most drivers using readl() or readl_relaxed() expect those to perform byte
| swaps on big-endian architectures, as the registers tend to be fixed endian

This was needed for getting UART to work correctly on a Big Endian ARC.

The ARC accessors originally were fine, and the bug got introduced
inadventently by commit b8a03302 ("ARCv2: barriers")

Fixes: b8a03302 ("ARCv2: barriers")
Link: http://lkml.kernel.org/r/201603100845.30602.arnd@arndb.de


Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: stable@vger.kernel.org  [4.2+]
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarLada Trimasova <ltrimas@synopsys.com>
[vgupta: beefed up changelog, added Fixes/stable tags]
Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent 2d746eeb

arch/arc/include/asm/io.h

+13 −5
Original line number Diff line number Diff line
@@ -129,15 +129,23 @@ 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

 * Relaxed API for drivers which can handle barrier ordering themselves

 *

 * Also these are defined to perform little endian accesses.

 * To provide the typical device register semantics of fixed endian,

 * swap the byte order for Big Endian

 *

 * http://lkml.kernel.org/r/201603100845.30602.arnd@arndb.de

 */

#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>