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    SubjectRe: [RFC] Fix Device Power Management States
    Hi!

    > > Well, "no DMA" needs to be part of definition, too, because some
    > > devices (USB) do DMA only if they have nothing to do.
    >
    > I don't understand; that doesn't sound healthy.

    It is not healthy. It is basicaly misdesigned piece of hardware called
    UHCI. It simply does DMA all the time :-(.

    > > if something like this gets merged, it will immediately break swsusp
    > > because initially no drivers will have "stop" methods.
    > >
    > > Passing system state down to drivers and having special "quiesce"
    > > (as discussed in rather long thread) state has advantage of
    > > automagicaly working on drivers that ignore u32 parameter of suspend
    > > callback (and that's most of them). David's patches do not bring us
    > > runtime suspend capabilities, but do not force us to go through all
    > > the drivers, either...
    >
    > Nothing is free. ;)
    >
    > We've been talking about creating and merging a sane power management
    > model for 3+ years now. It's always been known that the drivers will have
    > to be modified to support a sane model. It's a fact of life. At some
    > point, we have to bite the bullet and do the work. I see that time rapidly
    > approaching.
    >
    > I do not intend to merge a patch that will break swsusp in a stable
    > kernel. However, we do have this wonderful thing called the -mm tree in
    > which we can a) evolve the model, b) get large testing coverage and c)
    > solicit driver fixes.
    >
    > Once the swsusp consolidation is merged upstream, I will merge a new
    > device power model in -mm, and we can start working on the drivers. How
    > does that sound?

    It sounds like an acceptable plan. I see no real disadvantage in
    "suspend with parameter X means quiesce", and I think we'd get smaller
    patch that way, but if you go through -mm like this, we can do it.

    Pavel
    --
    Horseback riding is like software...
    ...vgf orggre jura vgf serr.
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