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SubjectRe: [PATCH 1/3] PM / sleep: New flag to speed up suspend-resume of suspended devices
On Thu, 27 Feb 2014, Rafael J. Wysocki wrote:

> > If the child knows about the problem beforehand, it can runtime-resume
> > the parent during its ->suspend.
>
> Well, it even should do that in those cases. We may need to deal with children
> that don't do that, though.
>
> > > Well, if power.fast_suspend set guarantees that ->suspend_late, ->suspend_noirq,
> > > ->resume_noirq, and ->resume_early will be skipped for a device, then we may
> > > restrict setting it for devices whose children have it set (or that have no
> > > children). Initially, that will be equivalent to setting it for leaf devices
> > > only, but it might be extended over time in a natural way.
> >
> > Initially, maybe.
>
> Of course initially.
>
> > But it's the wrong approach in general.
>
> In the long run - I agree.
>
> > The right approach is to restrict setting fast_suspend for devices whose
> > children don't mind their parent being suspended when their resume callbacks
> > run -- not for devices whose children also have fast_suspend set.
>
> I agree, but we need to know which children are OK with the parent being
> suspended. Having fast_suspend set is a good indication of that. :-)
>
> Of course, we may introduce a separate flag for that just fine if you prefer.
>
> > That's the point I've been trying to express all along.
>
> I see.

Okay. I'll wait to see the next version.

Alan Stern



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