From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Dave Airlie <airlied@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
"dri-devel" <dri-devel@lists.freedesktop.org>,
Linux PM list <linux-pm@vger.kernel.org>,
Alan Stern <stern@rowland.harvard.edu>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
linux-pci@vger.kernel.org
Subject: Re: runtime PM and special power switches
Date: Tue, 11 Sep 2012 22:55:10 +0200 [thread overview]
Message-ID: <201209112255.10486.rjw@sisk.pl> (raw)
In-Reply-To: <CAPM=9tzq2+LO2BzEmmByeozKzX6nswi1EwvEEM_bgo9kFv1hhA@mail.gmail.com>
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.
Thanks,
Rafael
next parent reply other threads:[~2012-09-11 20:55 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 ` Rafael J. Wysocki [this message]
2012-09-11 21:32 ` runtime PM and special power switches Alan Stern
2012-09-11 22:23 ` Rafael J. Wysocki
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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