| From | Kamal Mostafa <> | Subject | [PATCH 4.2.y-ckt 106/218] ARC: [BE] readl()/writel() to work in Big Endian CPU configuration | Date | Thu, 31 Mar 2016 13:15:19 -0700 |
| |
4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Lada Trimasova <ltrimas@synopsys.com>
commit f778cc65717687a3d3f26dd21bef62cd059f1b8b upstream.
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 b8a033023994 ("ARCv2: barriers")
Fixes: b8a033023994 ("ARCv2: barriers") Link: http://lkml.kernel.org/r/201603100845.30602.arnd@arndb.de Cc: Alexey Brodkin <abrodkin@synopsys.com> 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> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/arc/include/asm/io.h | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h index 694ece8..27b17ad 100644 --- a/arch/arc/include/asm/io.h +++ b/arch/arc/include/asm/io.h @@ -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> -- 2.7.4
|