From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7EB55C432C0 for ; Tue, 3 Dec 2019 05:51:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5CCB520684 for ; Tue, 3 Dec 2019 05:51:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727021AbfLCFvk (ORCPT ); Tue, 3 Dec 2019 00:51:40 -0500 Received: from esa1.mentor.iphmx.com ([68.232.129.153]:6594 "EHLO esa1.mentor.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726521AbfLCFvj (ORCPT ); Tue, 3 Dec 2019 00:51:39 -0500 IronPort-SDR: o/j+Ri+xO4fWTIVCdgPBUzjtzOJlOQ4wmggRu6QZca0TCBOkHqE4ZMckMY0XgpgEFCwVAkOZdJ zH0Di0t2eFwTMoCX5+Dmbv/B30Kz8UeQbcwSlJRrRyvBRAArhUElLv2NMKH+zppw4ZC7dOxlWK AOMf3uRfAIM2u7Wk4Qq86K3+6lV5vqjvPpzQSFfW8sP63eqIdEg5mIdaN5zTAybmjTxgYgnNgL KxJgiYocZbKXHSbByjv5bF9N1WRypaYrkWAm9RhI0RIYJkMYks64vQIn8f/LUTdW04Df3YiDyu xKI= X-IronPort-AV: E=Sophos;i="5.69,272,1571731200"; d="scan'208";a="45589731" Received: from orw-gwy-01-in.mentorg.com ([192.94.38.165]) by esa1.mentor.iphmx.com with ESMTP; 02 Dec 2019 21:51:38 -0800 IronPort-SDR: i8krjONcTTsnPkHY7SRiGdPmITr+0xNAXFXEgjkJWTG1D1tRaDcT2sdw0OnXTIXhUqEDFgzvAR dttKo+ORd63AvM4to/DyzDuJF57oI5Vi7/iYpzrQEkc3xIqj3eJT457bxirU8BrDkuqz8apUvw JxXTyf13gnmnt2Ln1nepE0IY1Dr7ZC1/mxI+i6nWcNIcJmX2GgkCgi2Uo1v6wmGd1b+yqVAN9T 0VLnn5Y5apijUzN7Hq0gIyZaQmf5LOaoYKcT6i2bJwuZAsOGE6Kp5TQMK0MgNeNdOFviPXHdfV l0k= Subject: Re: [PATCH v3 4/7] dt-bindings: gpio: Add gpio-repeater bindings To: Geert Uytterhoeven , Linus Walleij , Bartosz Golaszewski , Jonathan Corbet , Rob Herring , Mark Rutland , Eugeniu Rosca CC: Alexander Graf , Peter Maydell , Paolo Bonzini , Phil Reid , Marc Zyngier , Christoffer Dall , Magnus Damm , , , , , , References: <20191127084253.16356-1-geert+renesas@glider.be> <20191127084253.16356-5-geert+renesas@glider.be> From: Harish Jenny K N Message-ID: <11ae473f-cee1-241b-174c-915dc46209b1@mentor.com> Date: Tue, 3 Dec 2019 11:21:26 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191127084253.16356-5-geert+renesas@glider.be> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [137.202.0.90] X-ClientProxiedBy: svr-ies-mbx-01.mgc.mentorg.com (139.181.222.1) To svr-ies-mbx-01.mgc.mentorg.com (139.181.222.1) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 27/11/19 2:12 PM, Geert Uytterhoeven wrote: > Add Device Tree bindings for a GPIO repeater, with optional translation > of physical signal properties. This is useful for describing explicitly > the presence of e.g. an inverter on a GPIO line, and was inspired by the > non-YAML gpio-inverter bindings by Harish Jenny K N > [1]. > > Note that this is different from a GPIO Nexus Node[2], which cannot do > physical signal property translation. > > While an inverter can be described implicitly by exchanging the > GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags, this has its limitations. > Each GPIO line has only a single GPIO_ACTIVE_* flag, but applies to both > th provider and consumer sides: > 1. The GPIO provider (controller) looks at the flags to know the > polarity, so it can translate between logical (active/not active) > and physical (high/low) signal levels. > 2. While the signal polarity is usually fixed on the GPIO consumer > side (e.g. an LED is tied to either the supply voltage or GND), > it may be configurable on some devices, and both sides need to > agree. Hence the GPIO_ACTIVE_* flag as seen by the consumer must > match the actual polarity. > There exists a similar issue with interrupt flags, where both the > interrupt controller and the device generating the interrupt need > to agree, which breaks in the presence of a physical inverter not > described in DT (see e.g. [3]). > > [1] "[PATCH V4 2/2] gpio: inverter: document the inverter bindings" > https://lore.kernel.org/linux-gpio/1561699236-18620-3-git-send-email-harish_kandiga@mentor.com/ > > [2] Devicetree Specification v0.3-rc2, Section 2.5 > https://github.com/devicetree-org/devicetree-specification/releases/tag/v0.3-rc2 > > [3] "[PATCH] wlcore/wl18xx: Add invert-irq OF property for physically > inverted IRQ" > https://lore.kernel.org/linux-renesas-soc/20190607172958.20745-1-erosca@de.adit-jv.com/ > > Signed-off-by: Geert Uytterhoeven > --- > v3: > - New. > --- > .../bindings/gpio/gpio-repeater.yaml | 53 +++++++++++++++++++ > 1 file changed, 53 insertions(+) > create mode 100644 Documentation/devicetree/bindings/gpio/gpio-repeater.yaml > > diff --git a/Documentation/devicetree/bindings/gpio/gpio-repeater.yaml b/Documentation/devicetree/bindings/gpio/gpio-repeater.yaml > new file mode 100644 > index 0000000000000000..efdee0c3be43f731 > --- /dev/null > +++ b/Documentation/devicetree/bindings/gpio/gpio-repeater.yaml > @@ -0,0 +1,53 @@ > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/gpio/gpio-repeater.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: GPIO Repeater > + > +maintainers: > + - Harish Jenny K N > + - Geert Uytterhoeven > + > +description: > + This represents a repeater for one or more GPIOs, possibly including physical > + signal property translation (e.g. polarity inversion). > + > +properties: > + compatible: > + const: gpio-repeater > + > + "#gpio-cells": > + const: 2 > + > + gpio-controller: true > + > + gpios: > + description: > + Phandle and specifier, one for each repeated GPIO. > + > + gpio-line-names: > + description: > + Strings defining the names of the GPIO lines going out of the GPIO > + controller. > + > +required: > + - compatible > + - "#gpio-cells" > + - gpio-controller > + - gpios > + > +additionalProperties: false > + > +examples: > + # Device node describing a polarity inverter for a single GPIO > + - | > + #include > + > + inverter: gpio-repeater { > + compatible = "gpio-repeater"; > + #gpio-cells = <2>; > + gpio-controller; > + gpios = <&gpio 95 GPIO_ACTIVE_LOW>; > + }; just a suggestion: giving a gpio-line-names in the example would look useful.