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    SubjectRe: [RFC][PATCH] PM: Introduce core framework for run-time PM of I/O devices (rev. 8)
    On Wed, 8 Jul 2009, Rafael J. Wysocki wrote:

    > > I thought you wanted to avoid this sort of complication.
    >
    > I did, but there might be some benefits. For example, the timer and the work
    > structure provided by dev.power can be used for scheduling such operations
    > if they are defined at the core level.
    >
    > Suppose your device has 3 low power states D1 - D3 (like PCI) and you want it
    > to go into D1 first, then, after a delay, to D2 and finally, again after a
    > delay, to D3. Of course, if there's a resume in the meantime, it should cancel
    > whichever transition is in progress.
    >
    > pm_runtime_suspend() can be used for the first transition, but the bus type or
    > driver will have to provide its own mechanics for going down to D2 and D3,
    > which must be synchronized with its ->runtime_resume(). That might be tricky
    > and the core already has what's necessary (well, almost).

    Maybe we can provide a way for drivers to set up their own timer
    callback or work routine for use while the status is RPM_SUSPENDED.

    Alan Stern



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