Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751601Ab2JVIVW (ORCPT ); Mon, 22 Oct 2012 04:21:22 -0400 Received: from mail-wg0-f42.google.com ([74.125.82.42]:33432 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750793Ab2JVIVV (ORCPT ); Mon, 22 Oct 2012 04:21:21 -0400 MIME-Version: 1.0 In-Reply-To: <20121019181019.GP4730@atomide.com> References: <1350651909-5337-1-git-send-email-linus.walleij@stericsson.com> <20121019181019.GP4730@atomide.com> Date: Mon, 22 Oct 2012 10:21:19 +0200 Message-ID: Subject: Re: [PATCH v2] pinctrl: reserve pins when states are activated From: Linus Walleij To: Tony Lindgren Cc: Linus Walleij , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Stephen Warren , Anmar Oueja , Patrice Chotard , Jean Nicolas Graux , Loic Pallardy Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1554 Lines: 38 On Fri, Oct 19, 2012 at 8:10 PM, Tony Lindgren wrote: > [Me] >> Instead: let use reserve the pins when the state is activated >> and drop them when the state is disabled, i.e. when we move to >> another state. This way different devices/functions can use the >> same pins at different times. > > Hmm doesn't this mean that we are now doing lots of extra > reserving and dropping of pins? Performance is important from > latency point of view for cases where we need to remux pins > constantly runtime PM. It is only done in case the pinmux state is switched in runtime suspend/resume, so it's e.g. possible to just alter the pin config. But in general what you say is true. We used to to the same thing by having drivers call pinctrl_get()/pinctrl_put() in this case instead, but that went away with the introduction of states, so we cannot encode different pin sets with say pinctrl_get(dev, "foo")/pinctrl_get(dev, "bar") anymore since there is only one pinctrl handle per device, but multiple states. If this turns out to be a severe performance bottleneck, I suggest to add some additional constraint API, like pinctrl_set_pinmux_homegeneous_pinsets(true) that will at runtime select whether the pin allocation is done when getting the pinctrl handle instead. Yours, Linus Walleij -- 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/