From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754009AbaEMPml (ORCPT ); Tue, 13 May 2014 11:42:41 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:38795 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753259AbaEMPmg (ORCPT ); Tue, 13 May 2014 11:42:36 -0400 Message-ID: <53723D68.6010808@wwwdotorg.org> Date: Tue, 13 May 2014 09:42:32 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: FanWu CC: "linus.walleij@linaro.org" , "linux-kernel@vger.kernel.org" , "swarren@nvidia.com" , Chao Xie , Yilu Mao , Ning Jiang , Xiaofan Tian , Fangsuo Wu Subject: Re: [Pinctrl] A suggestion to avoid duplicated enabling operation on a pin's setting References: <534B558A.3040504@marvell.com> <534F8B35.7090103@marvell.com> <5366F387.4060402@marvell.com> <5367CD62.7030205@wwwdotorg.org> <5369E891.2020309@marvell.com> <53712D10.40003@wwwdotorg.org> <5371B36E.5030309@marvell.com> In-Reply-To: <5371B36E.5030309@marvell.com> X-Enigmail-Version: 1.5.2 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 On 05/12/2014 11:53 PM, FanWu wrote: ... > About the glitch I mentioned before, I want to make myself clear. > If there is a case like the following one: > pinctrl-0 = <&a_grp_settingA>; > pinctrl-1 = <&a_grp_settingB>; > "a_grp_settingA" and "a_grp_settingB" are used to described the same > Pin's different mux and function configuration > In my understanding, > When there is a need to switch Pin group state, the current code will > disable "a_grp_settingA" first ahead of enabling "a_grp_settingB", right ? Yes. > Do you mean the case I mentioned will not be a glitch ? I guess you're talking about that: >> In the original code, the Pin setting will be changed to the >> disabled/safe state when Pin state is switched if the old setting is not >> existed in new state rather than directly switched to the new Pin >> setting. Also a possible glitch? Yes, in this case, there is no glitch. However, there is certainly a change in HW configuration. A glitch is a temporary short-term accidental change in output value or configuration. In the case quoted immediately above, the change is permanent - at least until some other state is activated later. Hence, there is no glitch. However, there certainly is a change in HW configuration, and that could be just as problematic, depending on the HW and exact pin configuration.