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    SubjectRe: Linux 2.4.21-pre3-ac4
    On Tue, 2003-01-21 at 00:31, Alan Cox wrote:
    > On Tue, 2003-01-14 at 17:38, Benjamin Herrenschmidt wrote:
    > > > Fatal on PIIX PIO
    > >
    > > Ok, but PIIX runs on intel platforms with real IOs, so there is no need
    > > to perform a read... If we go the hwif->IOSYNC() way, we might well set
    > > it up to no-op on x86 PIO iops by default and read of alt-status on
    > > other archs if it's safe enough on other controllers/drives...
    > PIIX is also found on MIPS, IA-64 and some other platforms. I also fear
    > that bug may be far from unique

    Then we may want to have the actual implementation of the default iops
    IOSYNC() for PIO & MMIO be arch specific. I would suggest nothing for
    PIO on x86 and at least and mb() on others. For MMIO, then, we have the
    choice of reading the alt status, or reading the dma_base if any.

    Of course these are defaults, I expect controllers like ide-pmac to
    implement their own IOSYNC.

    That means that we must _both_ call IOSYNC and do the 400ns delay (I
    don't trust reading alt status to be enough, especially on MMIO based
    controlers, also, on ide-pmac, I plan to go read some other register

    What do you think ?

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