linux-kernel - Re: [linux-pm] [RFC,PATCHv3 0/3] sdhci runtime

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Date:	Wed, 2 Mar 2011 10:12:22 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Pierre Tardy <tardyp@...il.com>, <linux-kernel@...r.kernel.org>,
	<linux-pm@...ts.linux-foundation.org>, <linux-mmc@...r.kernel.org>
Subject: Re: [linux-pm] [RFC,PATCHv3 0/3] sdhci runtime_pm implementation

On Wed, 2 Mar 2011, Rafael J. Wysocki wrote:

> > > How it works is, basically, that when the device signals wakeup, it either
> > > causes a PME# signal to be raised (parallel PCI), or a PME Message to be
> > > sent upstream (PCIe).  In the first case it will cause a platform event
> > > (eg. ACPI GPE) to occur and the handle of that event will resume your
> > > device (using pm_request_resume()).  In the second case it will cause the PCIe
> > > root port handling the PME Message to generate an interrupt and the handler of
> > > that interrupt will resume your device.
> > Thanks, that explain a lot how it works.
> > What I still dont understand is that the wake source I'll have (e.g.
> > sd card insert) is still an interrupt source.
> > So it is supposed to generate interrupt until the interrupt source is
> > acknowledged.
> > Are we supposed to mask that interrupt source while suspended to make
> > sure we have either wake or interrupt?
> 
> I think the interrupt should be masked while suspended and the driver's resume
> routine should unmask it.

Right.  That's how the PCI-based USB host controller drivers work.  
The suspend routine disables interrupt generation and enables PME
wakeup signals, and the resume routine does the reverse.

Alan Stern

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