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    SubjectRe: [PATCH 3/4] atmel-mci: support multiple mmc slots
    On Wed, 24 Sep 2008 16:35:27 +0200
    Haavard Skinnemoen <haavard.skinnemoen@atmel.com> wrote:

    >
    > On AP7000, the clock line is shared. Do I have to run the clock at the
    > minimum of the two slots' maximum rates, or does it only matter when
    > the card is being accessed?
    >

    I'd say always. I'd never dare overclock something that's powered, even
    if we're not currently communicating with it.

    Remember to deal with the case of a powered but unclocked card. This
    will primarily happen during card init, but it could should up later as
    well if we start implementing aggressive power management.

    > > > > (This will also get a bit more painful when/if the core starts
    > > > > disabling the clock when a card is idle)
    > > >
    > > > The atmel-mci driver already stops the clock between requests.
    > >
    > > Then I expect a patch to remove that. Fiddling with the clock is
    > > dangerous and I've seen everything from hung cards to silently broken
    > > writes when you disable the clock too early after a request.
    >
    > Ok. I'll see if I can fix that -- I take it you want a patch for
    > 2.6.27, then?
    >

    .28 should be fine. It's a pretty uncommon bug.

    > > > >
    > > > > Fall back to polling?
    > > >
    > > > Probably, yes. Can I fall back to polling after the host has been
    > > > registered?
    > > >
    > >
    > > Hmm... no. Not sure how to handle this...
    >
    > I'll see if I can figure out a way to do it. I'm not giving it high
    > priority since it's a fairly obscure error case which shouldn't happen
    > with properly implemented board code.
    >

    Agreed.

    --
    -- Pierre Ossman

    Linux kernel, MMC maintainer http://www.kernel.org
    rdesktop, core developer http://www.rdesktop.org

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