From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932960Ab1ESMpq (ORCPT ); Thu, 19 May 2011 08:45:46 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:62402 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756595Ab1ESMpp (ORCPT ); Thu, 19 May 2011 08:45:45 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:reply-to:references :mime-version:content-type:content-disposition:in-reply-to :user-agent; b=kM6jopyxfRwznC1sktFvLcdJ59NJUopsCUpHml2HVDG6qXCGAR+4Jzy/5Aduycm4kz icIa//0pFO/5WBtKP0UYZXFt13ZrLUHxPmm9YvjPyfmvGbrTdkP7F2jM/f9ivfAVYFsQ iffCWZrWBJGAl8qzu/LPjiB1H2oDu8gB2VRac= Date: Thu, 19 May 2011 05:45:39 -0700 From: mark gross To: "Rafael J. Wysocki" Cc: markgross@thegnar.org, Raffaele Recalcati , linux-pm@lists.linux-foundation.org, davinci-linux-open-source@linux.davincidsp.com, linux-kernel@vger.kernel.org Subject: Re: [linux-pm] pm loss development Message-ID: <20110519124539.GA10262@gvim.org> Reply-To: markgross@thegnar.org References: <1305220265-9020-1-git-send-email-lamiaposta71@gmail.com> <201105180107.58078.rjw@sisk.pl> <20110518031203.GA3640@gvim.org> <201105182143.13237.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201105182143.13237.rjw@sisk.pl> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 18, 2011 at 09:43:13PM +0200, Rafael J. Wysocki wrote: > On Wednesday, May 18, 2011, mark gross wrote: > > On Wed, May 18, 2011 at 01:07:57AM +0200, Rafael J. Wysocki wrote: > > > On Saturday, May 14, 2011, mark gross wrote: > > > > On Fri, May 13, 2011 at 06:54:57PM +0200, Rafael J. Wysocki wrote: > > > > > On Friday, May 13, 2011, Raffaele Recalcati wrote: > > > > > > Hi Rafael, > > > > > > > > > > > > 2011/5/12 Rafael J. Wysocki : > > > > > > > On Thursday, May 12, 2011, Raffaele Recalcati wrote: > > > > > > >> What happen normally in runtime pm implementation is that every devices > > > > > > >> are switched off and are enabled only when needed. > > > > > > >> In our case instead we have a completely functional embedded system and, > > > > > > >> when an asyncrhonous event appear, we have only some tens milliseconds > > > > > > >> before the actual power failure takes place. > > > > > > >> This patchset add a support in order to switch off not vital part of the system, > > > > > > >> in order to allow the board to survive longer. > > > > > > >> This allow the possibility to save important data. > > > > > > > > > > > > > > OK, so first, who decides what parts of the system are vital and what aren't? > > > > > > > > > > > > Take a quick look at Documentation/power/loss.txt paragrpah "2.4 > > > > > > Power loss policies". > > > > > > You can decide what can be powered off. > > > > > > > > > > I read the patches. My question was about the general idea of who should > > > > > be responsible of making these decisions. > > > > > > > > I would expect the system integrator would based on the application the > > > > device is getting deployed into. > > > > > > > > A generic opportunistic policy for peripherals that are stateless and can > > > > be trivially power gated off/on from an ISR could be a default but, for > > > > peripherals that need to do some processing (like waiting on an eMMC DMA > > > > to complete) can take time to power down into a safe state. > > > > > > What do you mean by safe state? > > > > > I need to get more details on this but I assume its a state where the > > meta data of the file system is committed to the emmc before lights go > > off such that when power is reapplied that the damage isn't too big. > > I don't think you can guarantee that the metadata won't be damaged > without notifying the filesystem of the event (and making it react > appropriately). > true. I'm just brain storming what infrastructure would be needed to support such a feature. > > I've also heard some talk of sim card corruption risks but, I don't have > > first hand info on that. > > Well, I guess that might be prevented by the driver alone. Only the radio has a direct interface to the sim. (pretty sure anyway) so this would transfer into some AT commands pushed to the modem. --mark