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    SubjectRe: [PATCH] pata_it8213: MWDMA0 is unsupported
    Date
    On Thursday 26 November 2009 07:12:59 pm Sergei Shtylyov wrote:
    > Bartlomiej Zolnierkiewicz wrote:
    >
    > >>>>>MWDMA0 timings cannot be met with the PIIX based controller
    > >>>>>programming interface.
    > >>>
    > >>>>>This change should be safe as this is how we have been doing
    > >>>>>things in IDE it8213 host driver for years.
    > >>>
    > >>>>>Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
    > >>>>>---
    > >>>>>Verified with the documentation (similar case as with pata_efar).
    >
    > >>>>Uhhh, no...
    >
    > >>>>Too many damn drivers.
    >
    > >>>>Too much damn duplication.
    >
    > >>>>Too much damn subtle differences here and there.
    >
    > >>>>The hardware is probably fine for MWMDA0 when it comes to pata_{efar,it8213},
    > >>>>it just not documented properly in the data sheet.
    >
    > >>> How so with pata_efar? The active/recovery bitfields are still 2-bit
    > >>>wide, no?
    >
    > >>Yes but when TIMEx bit is disabled we are using XFER_PIO_SLOW timings.
    >
    > 600 ns cycle vs spec'ed 480 ns? Is it really worth it?

    960 ns actually

    > >>All data sheets including original Intel ones are a complete crap when it
    > >>comes to explicitly documenting this behavior.
    >
    > > OTOH all drivers set TIMEx for MWDMA0 currently.. ?
    >
    > ... which would give a grossly overclocked timing.

    Except ata_piix which blacklists MWDMA0 for _all_ PATA controllers.. :)

    I'm leaving my patches as they were for now, unless somebody wants to
    untangle this mess this is a safest and quickest way forward..

    --
    Bartlomiej Zolnierkiewicz


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