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ARC: [BE] readl()/writel() to work in Big Endian CPU configuration

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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 b8a0330239 ("ARCv2: barriers")

Fixes: b8a0330239 ("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: Lada Trimasova <ltrimas@synopsys.com>
[vgupta: beefed up changelog, added Fixes/stable tags]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Lada Trimasova 2016-03-09 20:21:04 +03:00 committed by Vineet Gupta
parent 2d746eeb4f
commit f778cc6571
1 changed files with 13 additions and 5 deletions
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18
arch/arc/include/asm/io.h
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@ -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>