lkml.org 
[lkml]   [2007]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
    Date
    >>>> And no, RMW on MMIO isn't "problematic" at all, either.
    >>>>
    >>>> An RMW op is a read op, a modify op, and a write op, all rolled
    >>>> into one opcode. But three actual operations.
    >>>
    >>> Maybe for some CPUs, but not all. ARM for instance can't use the
    >>> load exclusive and store exclusive instructions to MMIO space.
    >>
    >> Sure, your CPU doesn't have RMW instructions -- how to emulate
    >> those if you don't have them is a totally different thing.
    >
    > Let me say it more clearly: On ARM, it is impossible to perform atomic
    > operations on MMIO space.

    It's all completely beside the point, see the other subthread, but...

    Yeah, you can't do LL/SC to MMIO space; ARM isn't alone in that.
    You could still implement atomic operations on MMIO space by taking
    a lock elsewhere, in normal cacheable memory space. Why you would
    do this is a separate question, you probably don't want it :-)


    Segher

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-08-21 16:59    [W:0.020 / U:125.368 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site