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    SubjectRe: [PATCH 2.4.32] Fix AVM C4 ISDN card init problems with newer CPUs
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    Ar Iau, 2006-08-03 am 19:31 +0200, ysgrifennodd Karsten Keil:
    > Yes, that should be go in.
    >
    > AVM C4 ISDN NIC: Add three memory barriers, taken from 2.6.7,
    > (they are there in 2.6.17.7 too), to fix module initialization
    > problems appearing with at least some newer Celerons and
    > Pentium III.
    >
    > Acked-by: Karsten Keil <kkeil@suse.de>
    > Signed-off-by: Jukka Partanen <jspartanen@gmail.com>

    NAK: Alan Cox <alan@redhat.com>

    Two reasons

    #1 You should use cpu_relax in such loops
    #2 The readl (which c4inmeml is a pointless #define of) is defined to be
    a volatile reference itself

    That means that the real bug would appear to be different and either you
    have a gcc bug which is possible or you have something stranger going
    on, such as the continued polling busying the microcontroller the other
    end, in which case you need a delay not the lucky chance that mb() is
    slowish on some x86 systems.

    So you either want

    cpu_relax + other fixes
    or udelay(something)


    Alan

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