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    SubjectRe: Totally broken PCI PM calls
    Linus Torvalds writes:

    > On Mon, 11 Oct 2004, Benjamin Herrenschmidt wrote:
    > >
    > > Any reason why this totally broken code was ever merged upstream ?
    > Because it fixes a lot of drivers.
    > > Please, revert that to something sane before 2.6.9...
    > Nope. There's just too much confusion abou what the state thing means.
    > See the TG3 driver, for one, all the USB drivers for another.

    The USB drivers aren't a good example, they are currently quite broken
    as far as suspend/resume is concerned. They used to work just fine
    but got broken some time in the last few months.

    The problem I have at the moment is that PCI drivers get asked to go
    to D3 for both suspend-to-ram and suspend-to-disk. In particular the
    radeonfb driver wants to do different things in these two cases.

    Really, what is bogus is pci-driver.c thinking it can tell what state
    to ask the PCI device driver to put the device into from the system
    power state, without using any platform information. For suspend to
    ram, we may need to put devices into D2, D3hot or D3cold, depending on
    the motherboard design. For suspend to disk, we don't really want to
    change the device's power state at all, but just quiesce the device
    and save its state.

    In the radeonfb case, it needs to put the device into either D3hot or
    D3cold (depending on the motherboard design) for suspend to ram. For
    suspend to disk it doesn't want to do much of anything (otherwise we
    lose the console at that point).

    > The long-term solution is to make this thing be not a number at all, but a
    > restricted type (ie a "struct" with one member, or similar) to make sure
    > you _cannot_ mis-use it. As it is, most PCI drivers do seem to expect a
    > PCI suspend state.

    Maybe the real problem is that we are trying to use the device suspend
    functions for suspend-to-disk, when we don't really want to change the
    device's power state at all.

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