Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261534AbVDZUXx (ORCPT ); Tue, 26 Apr 2005 16:23:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261585AbVDZUXx (ORCPT ); Tue, 26 Apr 2005 16:23:53 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:45192 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S261534AbVDZUXm (ORCPT ); Tue, 26 Apr 2005 16:23:42 -0400 Date: Tue, 26 Apr 2005 22:23:02 +0200 From: Pavel Machek To: Dave Jones , Andrew Morton , Alan Stern , alexn@dsv.su.se, greg@kroah.com, gud@eth.net, linux-kernel@vger.kernel.org, linux-pci@atrey.karlin.mff.cuni.cz, jgarzik@pobox.com, cramerj@intel.com, linux-usb-devel@lists.sourceforge.net Subject: Re: [PATCH] PCI: Add pci shutdown ability Message-ID: <20050426202302.GC20109@elf.ucw.cz> References: <1114458325.983.17.camel@localhost.localdomain> <20050425145831.48f27edb.akpm@osdl.org> <20050425221326.GC15366@redhat.com> <20050426093939.GC4175@elf.ucw.cz> <20050426175041.GB23205@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050426175041.GB23205@redhat.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1627 Lines: 38 Hi! > > Well, you can do "half suspend to ram; change your frequency; half > > resume" today, and it should work, but I do not think you'll like the > > speed. > > Indeed. With people running things like cpuspeed daemons to dynamically > scale speed, this is going to be really painful. > Of course, any operation where we have to quiesce DMA is going to mean > we're increasing latency around the scaling operation, but we don't > have to go through all the hoops that are necessary when suspending. > Thankfully some of the more recent implementations of speed/voltage > scaling don't have this requirement. Good, because some devices really need DMA. (Won't audio skip, and USB break when you disable DMA? I do not see how cpufreq doing DMA disable can be usefull.) > > In a ideal world, calling device_suspend(PMSG_FREEZE) gets you exactly > > that, and we'll do our best to make it fast enough. > > > > OTOH it *needs* to switch consoles to text one (because X may be > > running DMA, right?); I do not think you'll like that one. > > That would be insane, and make cpufreq totally useless for anyone > running X, so no. This is one of the reasons the kernel needs to > arbitrate DMA on behalf of X. It just needs someone to do the work. Yes... But it also looks like a lot of work :-(. Pavel -- Boycott Kodak -- for their patent abuse against Java. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/