From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [linux-pm] [RFC][PATCH] PM: Introduce core framework for run-time PM of I/O devices (rev. 8) Date: Sat, 11 Jul 2009 13:08:42 +0200 Message-ID: <200907111308.44388.rjw@sisk.pl> References: <175E0F9A9EFCEA46A65F5552BB057298BB5F3EA2@bgsmsx502.gar.corp.intel.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from ogre.sisk.pl ([217.79.144.158]:55206 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751784AbZGKLIc (ORCPT ); Sat, 11 Jul 2009 07:08:32 -0400 In-Reply-To: <175E0F9A9EFCEA46A65F5552BB057298BB5F3EA2@bgsmsx502.gar.corp.intel.com> Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Mahalingam, Nithish" Cc: Magnus Damm , Alan Stern , Greg KH , LKML , ACPI Devel Maling List , Linux-pm mailing list , Ingo Molnar , Arjan van de Ven On Thursday 09 July 2009, Mahalingam, Nithish wrote: > Hi, Hi, > I am newbee to this mailing list. Please excuse me if I am talking nonsense here. > > > > On Thu, Jul 9, 2009 at 10:48 PM, Alan Stern wrote: > >> On Thu, 9 Jul 2009, Magnus Damm wrote: > >> > >>> Clocks should be stopped as soon as possible without any delay. The > >>> clock stopping is very cheap performance wise. Also, the clock > >> stopping is done on bus level without invoking any driver callbacks. > >>> Delaying the clock stopping does not make any sense to me. > >> > >> In that case the device driver or bus subsystem should manage the > >> device's clock directly. There's no need to tie it in with the runtime > >> PM framework. Simply start the clock before each I/O operation and > >> stop it afterward. > > > It's not that easy. The clock needs to be enabled to let the hardware > > device perform device specific stuff. For instance, the clock for the > > LCD controller needs to be on to redraw the screen. When the driver > > knows that it's done with the clock it can notify the bus using > > Runtime PM. > > Is there any plan to look into the "Clock Framework" that was developed as > part of OMAP and extending this to make it generic for all platforms? I don't have any plan to do that and I heaven't heard of anyone planning to do it. Best, Rafael