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=-14.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 4AC59C43215 for ; Wed, 27 Nov 2019 08:43:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 291402084B for ; Wed, 27 Nov 2019 08:43:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726876AbfK0InJ (ORCPT ); Wed, 27 Nov 2019 03:43:09 -0500 Received: from xavier.telenet-ops.be ([195.130.132.52]:48454 "EHLO xavier.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726558AbfK0InJ (ORCPT ); Wed, 27 Nov 2019 03:43:09 -0500 Received: from ramsan ([84.195.182.253]) by xavier.telenet-ops.be with bizsmtp id Wwiu2100X5USYZQ01wiuc6; Wed, 27 Nov 2019 09:43:07 +0100 Received: from rox.of.borg ([192.168.97.57]) by ramsan with esmtp (Exim 4.90_1) (envelope-from ) id 1iZsuU-0000xl-Oj; Wed, 27 Nov 2019 09:42:54 +0100 Received: from geert by rox.of.borg with local (Exim 4.90_1) (envelope-from ) id 1iZsuU-0004Or-Ld; Wed, 27 Nov 2019 09:42:54 +0100 From: Geert Uytterhoeven To: Linus Walleij , Bartosz Golaszewski , Jonathan Corbet , Rob Herring , Mark Rutland , Harish Jenny K N , Eugeniu Rosca Cc: Alexander Graf , Peter Maydell , Paolo Bonzini , Phil Reid , Marc Zyngier , Christoffer Dall , Magnus Damm , linux-gpio@vger.kernel.org, linux-doc@vger.kernel.org, devicetree@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, Geert Uytterhoeven Subject: [PATCH v3 4/7] dt-bindings: gpio: Add gpio-repeater bindings Date: Wed, 27 Nov 2019 09:42:50 +0100 Message-Id: <20191127084253.16356-5-geert+renesas@glider.be> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191127084253.16356-1-geert+renesas@glider.be> References: <20191127084253.16356-1-geert+renesas@glider.be> Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org 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>; + }; -- 2.17.1