linux-kernel - Re: [linux-pm] [patch update 2 fix] PM: Introduce core framework for run-time PM of I/O devices

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Date:	Mon, 22 Jun 2009 06:49:15 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Greg KH <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [linux-pm] [patch update 2 fix] PM: Introduce core framework
 for  run-time PM of I/O devices

On Mon, 22 Jun 2009 16:27:29 +0900
Magnus Damm <magnus.damm@...il.com> wrote:

> On Mon, Jun 22, 2009 at 3:43 PM, Arjan van de
> Ven<arjan@...radead.org> wrote:
> > On Mon, 22 Jun 2009 15:20:43 +0900
> > Magnus Damm <magnus.damm@...il.com> wrote:
> >
> >> On Sat, Jun 20, 2009 at 11:30 PM, Alan
> >> Stern<stern@...land.harvard.edu> wrote:
> >> > Some more thoughts...
> >> >
> >> > Magnus, you might have some insights here.  It occurred to me
> >> > that some devices can switch power levels very quickly, and the
> >> > drivers might therefore want the runtime suspend and resume
> >> > methods to be called as soon as possible, even in interrupt
> >> > context.
> >>
> >> I'd like to call pm_request_suspend() from interrupt context. I
> >> don't
> >
> > there are some really strong reasons to at least be able to call the
> > resume function from an interrupt handler.... shared interrupts are
> > one of them.
> 
> I suppose you mean that you need to resume the hardware device before
> you can check if it has a pending interrupt source? If so then you
> also mean that suspended hardware devices may generate interrupts, no?

yes and no. For the shared interrupt case.. no.
but yes for the hw I have in mind (and on my desk ;-) that can happen
as well from the device itself.

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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