linux-kernel - Re: [patch update] Re: [linux-pm] Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code)

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Message-Id: <200906110115.30729.oliver@neukum.org>
Date:	Thu, 11 Jun 2009 01:15:30 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch update] Re: [linux-pm] Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code)

Am Mittwoch, 10. Juni 2009 23:31:13 schrieb Rafael J. Wysocki:
> > > +/**
> > > + * pm_check_children - Check if all children of a device have been
> > > suspended. + * @dev: Device to check.
> > > + *
> > > + * Returns 0 if all children of the device have been suspended or
> > > -EBUSY + * otherwise.
> > > + */
> >
> > We might want to do a runtime suspend even if the device's children
> > aren't already suspended.  For example, you could suspend a link while
> > leaving the device on the other end of the link at full power --
> > especially if powering down the device is slow but changing the link's
> > power level is fast.
>
> Well, this means that the dependencies between devices in the device tree
> are pretty much useless for the run-time PM as far as the core is
> concerned.  In which case, why did you mention them at all?

Some bussystems need this constraint others don't or only for some nodes.
We need a way to communicate this to the core.

	Regards
		Oliver


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