From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com Subject: Re: [PATCH] implement pm_ops.valid for everybody Date: Fri, 23 Mar 2007 09:15:17 -0400 Message-ID: <20070323131515.GA12226@atomide.com> References: <200703221344.l2MDi2Q9007989@olwen.urbana.css.mot.com> <200703221129.28722.david-b@pacbell.net> <20070322192647.GB20605@atomide.com> <200703221416.27103.david-b@pacbell.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <200703221416.27103.david-b@pacbell.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: David Brownell Cc: alexey.y.starikovskiy@intel.com, ben@simtec.co.uk, linux-arm@lists.arm.linux.org.uk, dirk.behme@de.bosch.com, pavel@ucw.cz, johannes@sipsolutions.net, nico@cam.org, linux-pm@lists.linux-foundation.org, g.liakhovetski@gmx.de List-Id: linux-pm@vger.kernel.org * David Brownell [070322 17:29]: > On Thursday 22 March 2007 12:26 pm, Tony Lindgren wrote: > > = > > In addition to offering wakeup events for individual devices, > > the device suspend states should be something like retention > > and suspend, where: > = > Maybe ... worth discussing. Most PCI drivers don't make > that distinction, although they could (see below). > = > What they do instead is assume the lowest device power state > ("suspend"), and re-initialize in resume(). If Linux starts to > support standby and STR modes properly ... then it'd make sense > to teach more PCI drivers to try using "retention" states. But > those drivers would still need to be prepared to re-init. I agree, in general we should start taking advantage of the device power states. = = > > Retention is where clocks are off for a device, but power is on. > > In this case the device registers are maintained in hardware. > = > Analagous to PCI D1 or D2. Hmmm, I think with PCI it's just numbering where the power consumption decreases as the nuber increases except for D3hot and D3cold. = > > Suspend is where clocks and power are off. In this state the > > device registers are maintained in software. > = > Analagous to PCI D3, especially D3cold ... although PCI D3 > certainly allows the Vaux "power well" to power some parts > of the device, so that not all register values get reset. Maybe actually D3hot =3D retention and D3cold =3D suspend? = PCI SOCs CLOCKS POWER D3hot retention off on D3cold suspend off off = > > Laptops mostly have suspend, while socs allow both retention > > and suspend in many cases. > = > Not quite true, as noted above. There are differences in how > things are factored, but those mechanisms exist in both x86 > and SOC worlds. One key difference from a Linux perspective > is probably that without ACPI in the way, a SOC design can > make much better use of the hardware PM capabilities. > = > Very few non-USB drivers address "retention" modes on laptops; > USB host controller drivers need it to handle "remote wakeup", > which one expects to work from "standby" and suspend-to-RAM. > (Plus potentialy suspend-to-disk, but that's uncommon.) Yeah, OK. Tony