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    SubjectRe: TG3 data corruption (TSO ?)

    > > semantics. At least what is implemented currently on PowerPC is the
    > > __raw_* versions which not only have no barriers at all (they don't even
    > > order between MMIOs, for example, readl might cross writel), and do no
    > > endian swap. Quite a mess of semantics if you ask me... Then there has
    > __writel/__readl seems more in keeping for just not locking.

    Not locking... you mean not ordering I suppose. Ok, so the question is
    no ordering at all (that is even between MMIO read/writes, thus a
    __readl can cross a __writel), or just no ordering between MMIO and
    cacheable storage ?

    It's an important difference and both have their use. For example, on
    PowerPC, if I completely remove barriers, I get the first semantic and I
    get the ability to write combine on non-cacheable storage as a benefit
    (provided we add an ioremap_wc or such, as the Guarded bit we set on
    normal non-cacheable space does also prevent write combining on most
    implementations). However, if I keep at least ordering between MMIOs,
    then I leave an eieio in there, which is not nearly as expensive than a
    full sync but will not order cacheable cs. non-cacheable. However, it
    will also prevent write combine as far as I remember.


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      Last update: 2006-09-10 03:21    [W:0.052 / U:126.692 seconds]
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