From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753534AbZBPWsK (ORCPT ); Mon, 16 Feb 2009 17:48:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751285AbZBPWr4 (ORCPT ); Mon, 16 Feb 2009 17:47:56 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:43736 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751256AbZBPWrz (ORCPT ); Mon, 16 Feb 2009 17:47:55 -0500 Date: Mon, 16 Feb 2009 23:47:41 +0100 From: Pavel Machek To: Roland Dreier Cc: Arjan van de Ven , "Rafael J. Wysocki" , pm list , LKML , Arve Hj??nnev??g , Alan Stern , Benjamin Herrenschmidt , Nigel Cunningham , Matthew Garrett , mark gross , "Woodruff, Richard" , Uli Luckas , Igor Stoppa , Brian Swetland , Len Brown Subject: Re: [RFD] Automatic suspend Message-ID: <20090216224741.GE1370@ucw.cz> References: <200902160010.16955.rjw@sisk.pl> <20090215164456.34aef7e8@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun 2009-02-15 22:23:04, Roland Dreier wrote: > > > (2) put given subset of devices into low power states whenever they > > > are not used, without putting the entire system into a sleep state. > > > For (2), for me the answer is very obvious: > > > The Device Driver needs to make the decision to put the device to sleep. > > There are no ifs and buts about this. > > For PC-like systems this is probably all that needs to be said. However > for highly integrated SoC systems (as Android is obviously targeting) > there is another level of complexity due to the interdependency among > various devices... eg things like if I know the SD controller and the > wifi chip are both asleep then I can put my SDIO controller to sleep; > and if the SDIO controller and the NAND controller are both asleep then > I can stop clock X and save more power; etc etc. > > This is what the PowerOp/DPM work was all about. Unfortunately that > doesn't seem to have made much progress upstream. But there's no doubt > in my mind that we need some framework beyond individual drivers that > manages the system's power as a whole. And the current device tree is > probably not sufficient -- eg the bus hierarchy of a device may not > match up with the clock tree at all. Well, that's why clock framework exists. But none of this is visible to userland. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html