linux-kernel - Re: [RFC][PATCH] PM: Introduce core framework for run-time PM of I/O devices (rev. 8)

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Message-ID: <Pine.LNX.4.44L0.0907081707090.22618-100000@iolanthe.rowland.org>
Date:	Wed, 8 Jul 2009 17:09:08 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Magnus Damm <magnus.damm@...il.com>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Greg KH <gregkh@...e.de>, LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [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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