Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751711Ab3FYO1j (ORCPT ); Tue, 25 Jun 2013 10:27:39 -0400 Received: from mail-oa0-f52.google.com ([209.85.219.52]:50769 "EHLO mail-oa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751177Ab3FYO1i (ORCPT ); Tue, 25 Jun 2013 10:27:38 -0400 MIME-Version: 1.0 In-Reply-To: <51C4C2ED.5090505@wwwdotorg.org> 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> Date: Tue, 25 Jun 2013 16:27:37 +0200 Message-ID: Subject: Re: [PATCH 2/2] Make non-linear GPIO ranges accesible from gpiolib From: Linus Walleij To: Stephen Warren 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 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: 1858 Lines: 47 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. 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/