lkml.org 
[lkml]   [2016]   [Mar]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.2.y-ckt 106/218] ARC: [BE] readl()/writel() to work in Big Endian CPU configuration
    Date
    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
    \
     
     \ /
      Last update: 2016-03-31 23:21    [W:2.263 / U:1.288 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site