Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752537Ab3FYPT1 (ORCPT ); Tue, 25 Jun 2013 11:19:27 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:46356 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752246Ab3FYPTV (ORCPT ); Tue, 25 Jun 2013 11:19:21 -0400 Message-ID: <51C9B4F5.6070008@wwwdotorg.org> Date: Tue, 25 Jun 2013 09:19:17 -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: Linus Walleij CC: Christian Ruppert , Patrice CHOTARD , "linux-kernel@vger.kernel.org" , Grant Likely , Rob Herring , Rob Landley , Sascha Leuenberger , Pierrick Hascoet , "devicetree-discuss@lists.ozlabs.org" , "linux-doc@vger.kernel.org" , Alexandre Courbot Subject: Re: [PATCH 2/2] Make non-linear GPIO ranges accesible from gpiolib References: <1371128132-18266-2-git-send-email-christian.ruppert@abilis.com> <51BA3BC1.3090109@wwwdotorg.org> <20130614091241.GA23745@ab42.lan> <51C1F42E.5090107@wwwdotorg.org> <51C1F82C.4020502@wwwdotorg.org> <20130620115710.GB942@ab42.lan> <51C4C2ED.5090505@wwwdotorg.org> In-Reply-To: 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: 2085 Lines: 49 On 06/25/2013 08:27 AM, Linus Walleij wrote: > On Fri, Jun 21, 2013 at 11:17 PM, Stephen Warren wrote: > >> When I pushed for the concept of groups, I intended it to mean precisely >> one single thing. The points below describe this. >> >> 1) A pin is a single pin/ball/pad on the package. >> >> 2) Some register fields affect just a single pin. For example, there may >> be a register field that affects pin A8's mux setting only. >> >> 3) Some register fields affect multiple pins at once. For example, >> perhaps one register field affects both pin A8's an pin A7's mux setting >> at once. >> >> 4) Depending on HW design, all register fields might be of type >> described at (2) above, or all of the type described at (3) above, or a >> mixture of both. Tegra is a mixture. >> >> 5) I expect the concept of a pin group to solely represent the various >> groups of pins affected by each register field; in (2) above one pin per >> group, in (3) above many pins per group. >> >> Thus, to my mind, a pin group is purely a HW concept, and dictated >> purely by HW design. > > This we can discuss perpetually it seems. > > For Nomadik, as I've pointed out in the past it is actually: > > (6): it is one register/set if bits per pin, BUT the register settings > pertain to physical lines having electrical settings which postulate > that they be handled in batch or wreak havoc. > > I.e. it is a HW limitation in the *silicon* of *all* implementations, > but that is *not* expressed in the register map. > > For the practical consequences see __nmk_config_pins if (glitch) > runpath. Handling this as a group makes perfect sense from > a hardware point of view. OK, so there are certainly some HW designs that may benefit from using groups even where the registers are per-pin. Using them there makes sense. -- 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/