From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Dave Airlie <airlied@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
"dri-devel" <dri-devel@lists.freedesktop.org>,
Linux PM list <linux-pm@vger.kernel.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
linux-pci@vger.kernel.org
Subject: Re: runtime PM and special power switches
Date: Wed, 12 Sep 2012 00:23:11 +0200 [thread overview]
Message-ID: <201209120023.11662.rjw@sisk.pl> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1209111730340.22718-100000@netrider.rowland.org>
On Tuesday, September 11, 2012, Alan Stern wrote:
> On Tue, 11 Sep 2012, Rafael J. Wysocki wrote:
>
> > Hi,
> >
> > On Tuesday, September 11, 2012, Dave Airlie wrote:
> > > Hi Rafael,
> > >
> > > I've been investigating runtime PM support for some use-cases on GPUs.
> > >
> > > In some laptops we have a secondary GPU (optimus) that can be powered
> > > up for certain 3D tasks and then turned off when finished with. Now I
> > > did an initial pass on supporting it without using the kernel runtime
> > > PM stuff, but Alan said I should take a look so here I am.
> >
> > Alan Stern or Alan Cox? :-)
> >
> > > While I've started to get a handle on things, we have a bit of an
> > > extra that I'm not sure we cater for.
> > >
> > > Currently we get called from the PCI layer which after we are finished
> > > with our runtime suspend callback, will go put the device into the
> > > correct state etc, however on these optimus/powerxpress laptops we
> > > have a separate ACPI or platform driver controlled power switch that
> > > we need to call once the PCI layer is finished the job. This switch
> > > effectively turns the power to the card completely off leaving it
> > > drawing no power.
> > >
> > > No we can't hit the switch from the driver callback as the PCI layer
> > > will get lost, so I'm wondering how you'd envisage we could plug this
> > > in.
> >
> > Hmm. In principle we might modify pci_pm_runtime_suspend() so that it
> > doesn't call pci_finish_runtime_suspend() if pci_dev->state_saved is
> > set. That would actually make it work in analogy with pci_pm_suspend_noirq(),
> > so perhaps it's not even too dangerous.
>
> This sounds more like a job for a power domain. Unless the power
> switch is already in the device hierarchy as a parent to the PCI
> device.
Good idea. :-)
Thanks,
Rafael
next prev parent reply other threads:[~2012-09-11 22:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAPM=9tzq2+LO2BzEmmByeozKzX6nswi1EwvEEM_bgo9kFv1hhA@mail.gmail.com>
2012-09-11 20:55 ` runtime PM and special power switches Rafael J. Wysocki
2012-09-11 21:32 ` Alan Stern
2012-09-11 22:23 ` Rafael J. Wysocki [this message]
2012-09-11 22:23 ` Dave Airlie
2012-09-11 22:58 ` Rafael J. Wysocki
2012-09-12 5:13 ` Dave Airlie
2012-09-12 6:09 ` Dave Airlie
2012-09-18 21:47 ` Rafael J. Wysocki
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