Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754730Ab3EPWIk (ORCPT ); Thu, 16 May 2013 18:08:40 -0400 Received: from mail-ea0-f177.google.com ([209.85.215.177]:56117 "EHLO mail-ea0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753473Ab3EPWIj (ORCPT ); Thu, 16 May 2013 18:08:39 -0400 From: Tomasz Figa To: Doug Anderson Cc: Kukjin Kim , Olof Johansson , Stephen Warren , Thomas Abraham , Linus Walleij , Prathyush K , linux-samsung-soc , "linux-kernel@vger.kernel.org" , Heiko =?ISO-8859-1?Q?St=FCbner?= Subject: Re: [PATCH 1/2] pinctrl: samsung: fix suspend/resume functionality Date: Fri, 17 May 2013 00:08:34 +0200 Message-ID: <2099430.Q29j0K3hPy@flatron> User-Agent: KMail/4.10.3 (Linux/3.9.2-gentoo; KDE/4.10.3; x86_64; ; ) In-Reply-To: References: <1368724352-10849-1-git-send-email-dianders@chromium.org> <2469545.4zh8j9i5RI@flatron> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2780 Lines: 60 On Thursday 16 of May 2013 14:51:53 Doug Anderson wrote: > Tomasz, > > On Thu, May 16, 2013 at 2:27 PM, Tomasz Figa wrote: > > OK. I will be fine to go with your patches, after addressing the > > comments. In the end it's good that you posted them, as reviewing > > them allowed me to find even better ways of doing some things than I > > had in mine ;) . > Yes. I often find that the best way to review code is to think about > how I would implement it myself. Certainly I think we've ended up > with something better / less buggy this way. ;) > > > How all of this works is basically a good question. I couldn't find > > any > > mention about pins switching from power down to normal mode in the > > documentation, but maybe there is a small side note somewhere, which I > > could miss. > > > > On S3C6410, for example, there are two modes. State is switched to > > power down mode automatically, but can be switched out either > > automatically on wake-up (exact timing is unknown to me) or by > > clearing a special bit, depending on value of other special bit. > > > > IMHO this is rather important, so we should find out how it work on > > other SoCs and make the code account for it. > > Agreed that it's important. ...but it's also good not to have tons of > complexity when it's not needed. It sounds like S3C6410 could be > handled OK by just using the special bits and waiting to take things > out of power down mode. > > ...thinking about it, all SoCs that have power down modes (which you > _must_ have if your pinctrl state is lost across a low power) would be > slightly broken if they didn't have a bit to switch out of power down > mode. Otherwise you're asking for at least some type of glitch > because you'll end up in the default state of pins for a little while > during resume. > > That's not to say that there aren't broken SoCs out there and it's > entirely possible that people even designed systems around them > (knowing that the default state of each pin after wakeup is not > harmful to whatever is connected to that pin). If there are any cases > like this then they would need the special code like my V1 patch had. > Do you know of any SoCs like this that we need to support on kernel > 3.10 and higher? Hmm, I just checked documentation of S3C2440 and S3C2416 they seem to retain GPIO settings completely in sleep mode. This would mean that they don't require any suspend/resume support in pinctrl driver. Heiko, can you confirm this? Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/