From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759921AbYD2QWn (ORCPT ); Tue, 29 Apr 2008 12:22:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753178AbYD2QWg (ORCPT ); Tue, 29 Apr 2008 12:22:36 -0400 Received: from gateway.drzeus.cx ([85.8.24.16]:57767 "EHLO smtp.drzeus.cx" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751257AbYD2QWf (ORCPT ); Tue, 29 Apr 2008 12:22:35 -0400 Date: Tue, 29 Apr 2008 18:22:08 +0200 From: Pierre Ossman To: Tadeusz Gozdek Cc: linux-kernel@vger.kernel.org, marcel@holtmann.org Subject: Re: Fwd: [PATCH] [MMC] fix clock problem in PXA255/270 Message-ID: <20080429182208.70e1053e@mjolnir.drzeus.cx> In-Reply-To: <60c632a5.15d4db9c.4816f8d4.b398b@o2.pl> References: <441f2104.26c7abf7.48157da1.e45c7@o2.pl> <20080428152859.05efccf7@mjolnir.drzeus.cx> <61fb248d.11640040.4816c4ed.cc@o2.pl> <20080429113946.1ba93ef5@mjolnir.drzeus.cx> <60c632a5.15d4db9c.4816f8d4.b398b@o2.pl> X-Mailer: Claws Mail 3.3.1 (GTK+ 2.12.9; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Apr 2008 12:30:44 +0200 Tadeusz Gozdek wrote: > OK probably I didn't understand your policy. I ever thought that the host controller should know, when the clock should be off. No, it's not because it's not my policy, but because the kernel tries to avoid handling "policy". :) It is common to talk about software that implements "policy" or "mechanism". "mechanism" is simple the act of performing a given, well defined task (e.g. turn on LED A). "policy" on the other hand is selecting an action when there are multiple, equally valid actions. Usually this involves the user, directly or indirectly. The kernel tries to stay clear of "policy" as it is a complex problem that is better solved per system, in user space. So what I meant when I said that this is policy, I was saying that this is a "policy" kind of decision that needs to be configurable from user space. > The PXA controller is different and it was the simples (but effective) way to solve this difference. Different in what regard? Or are you referring to the already present clock fudging in the driver? > > So, I hope it will be usable for people which has problem with "always on" clock, until you solve it in different way (if you going to do this). > This is a project that has been popping up now and then, but the big thing that is lacking is someone who is able to actually measure if there is a power gain from this. I don't want to add a lot of code that isn't doing any good, so I want hard numbers. Rgds -- -- Pierre Ossman Linux kernel, MMC maintainer http://www.kernel.org PulseAudio, core developer http://pulseaudio.org rdesktop, core developer http://www.rdesktop.org