Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261513AbVDZRxi (ORCPT ); Tue, 26 Apr 2005 13:53:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261706AbVDZRwf (ORCPT ); Tue, 26 Apr 2005 13:52:35 -0400 Received: from mx1.redhat.com ([66.187.233.31]:5304 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S261513AbVDZRvN (ORCPT ); Tue, 26 Apr 2005 13:51:13 -0400 Date: Tue, 26 Apr 2005 13:50:42 -0400 From: Dave Jones To: Pavel Machek Cc: 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: <20050426175041.GB23205@redhat.com> Mail-Followup-To: Dave Jones , Pavel Machek , 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 References: <1114458325.983.17.camel@localhost.localdomain> <20050425145831.48f27edb.akpm@osdl.org> <20050425221326.GC15366@redhat.com> <20050426093939.GC4175@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050426093939.GC4175@elf.ucw.cz> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1373 Lines: 32 On Tue, Apr 26, 2005 at 11:39:39AM +0200, Pavel Machek wrote: > 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. > 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. Dave - 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/