From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757569Ab2IKUtM (ORCPT ); Tue, 11 Sep 2012 16:49:12 -0400 Received: from ogre.sisk.pl ([193.178.161.156]:48174 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756233Ab2IKUsy (ORCPT ); Tue, 11 Sep 2012 16:48:54 -0400 From: "Rafael J. Wysocki" To: Dave Airlie Subject: Re: runtime PM and special power switches Date: Tue, 11 Sep 2012 22:55:10 +0200 User-Agent: KMail/1.13.6 (Linux/3.6.0-rc5+; KDE/4.6.0; x86_64; ; ) Cc: LKML , "dri-devel" , Linux PM list , Alan Stern , Alan Cox , linux-pci@vger.kernel.org References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201209112255.10486.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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