Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758593Ab3FMTbX (ORCPT ); Thu, 13 Jun 2013 15:31:23 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:36166 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751999Ab3FMTbW (ORCPT ); Thu, 13 Jun 2013 15:31:22 -0400 Message-ID: <51BA1E06.6020705@wwwdotorg.org> Date: Thu, 13 Jun 2013 13:31:18 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Tony Lindgren CC: Linus Walleij , Linus Walleij , Greg Kroah-Hartman , Stephen Warren , Kevin Hilman , Wolfram Sang , Dmitry Torokhov , "linux-kernel@vger.kernel.org" , Hebbar Gururaja , Mark Brown , "linux-arm-kernel@lists.infradead.org" , Ulf Hansson Subject: Re: [PATCH] drivers: pinctrl: add active state to core References: <1370938616-5952-1-git-send-email-linus.walleij@stericsson.com> <51B75148.5080701@wwwdotorg.org> <20130612183345.GU8164@atomide.com> In-Reply-To: <20130612183345.GU8164@atomide.com> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2709 Lines: 60 On 06/12/2013 12:33 PM, Tony Lindgren wrote: > * Linus Walleij [130611 12:59]: >> On Tue, Jun 11, 2013 at 6:33 PM, Stephen Warren wrote: >>> On 06/11/2013 02:16 AM, Linus Walleij wrote: >>>> From: Linus Walleij >>>> >>>> In addition to the recently introduced pinctrl core >>>> control, the PM runtime pin control for the OMAP platforms >>>> require a fourth state in addtition to the default, idle and >>>> sleep states already handled by the core: an explicit "active" >>>> state. Let's introduce this to the core in addition to the >>>> other states already defined. >>> >>> Surely "default" /is/ "active"? That's what it's meant so far. >> >> I thought so too, until Tony informed us that in the OMAP world >> this state is not always the active one. >> >> But I don't know the exact reasons for. >> >> I guess that some "default" states on the OMAP may mean these >> are configured as decoupled, inactive, until explicitly activated >> or something like that. > > The main reason is that remuxing all the pins for a device for > PM runtime suspend and resume is not necessary. Most pins are > static and configured once during the consumer driver probe. > And in most cases, remuxing only one pin for the rx line is > needed. This is performance critical as it may need to be done > constantly while entering and exiting idle, and remuxing all the > pins is just a waste of cycles. Then isn't the correct solution to optimize the code that switches between states, so that it only reprograms the pins/groups necessary? Inventing extra states just to work around that issue seems quite wrong. So, I think you're relying on: default: Set up everything static. active: flip just a few pins to active state. idle: flip just a few pins to idle state. ... and assuming that the default->active or default->idle transitions will not affect any pins that are used in default, but not used in active/idle. However, that very specifically isn't the case; pinctrl drivers are allowed to force unused pins back to some default unused state when the pinctrl state that's being switched to doesn't mention them, and hence this concept won't work in general. Also, if default uses more pins that active, when you switch to active, those pins won't be marked as owned any more, I think, so something else could in theory grab them. At least, debugfs wouldn't be entirely accurate any more. -- 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/