From patchwork Wed Oct 29 14:04:17 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: kamlakant.patel@linaro.org X-Patchwork-Id: 39782 Return-Path: X-Original-To: linaro@patches.linaro.org Delivered-To: linaro@patches.linaro.org Received: from mail-wi0-f199.google.com (mail-wi0-f199.google.com [209.85.212.199]) by ip-10-151-82-157.ec2.internal (Postfix) with ESMTPS id 239EB24046 for ; Wed, 29 Oct 2014 14:04:34 +0000 (UTC) Received: by mail-wi0-f199.google.com with SMTP id r20sf1973563wiv.10 for ; Wed, 29 Oct 2014 07:04:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:delivered-to:from:to:cc:subject:date:message-id :mime-version:sender:precedence:list-id:x-original-sender :x-original-authentication-results:mailing-list:list-post:list-help :list-archive:list-unsubscribe:content-type; bh=6E+oe4iTa8zzlDQH3/TCXfu1VSsXQgxaBaMI5c5j6Po=; b=ZlKbUUbZn7TTgYCJ+9nJcygX6H6W4HfWvMT0igp4LNJB06w1b3Nj31336YIEhWs2o/ 55Gv/x2IdAmpxSwsra6bAta51wC//WXgQxvcfCfTZQXvS3fReLaiBgbezDVydcbB4CwO csWXhdt/cs2YrM817f4eEBIDkmMNkySN1T47aronmLx9l2ggrJmKygB6L09icTtsKkmH Klo4Ts7Hz/6EdqYZa05VWiKwBQsZ1QP1Dra1AZF4bJgF93I+Vio3zJPGhWncGtrM0QgX zq8dpvqDqoBORbWZf8wnsM6PKObVovtUJxexieVV5spaU/4T5cG7gohlbcslA7MTmrIy LTqQ== X-Gm-Message-State: ALoCoQlD0gUEUeATHjUV7a1hnVPTrMmCSPb53ERDX3gbhcR7cha9tLucvzM8y/DwZiEXTS4BLdqb X-Received: by 10.112.142.36 with SMTP id rt4mr1774487lbb.3.1414591472910; Wed, 29 Oct 2014 07:04:32 -0700 (PDT) X-BeenThere: patchwork-forward@linaro.org Received: by 10.152.9.168 with SMTP id a8ls191981lab.55.gmail; Wed, 29 Oct 2014 07:04:32 -0700 (PDT) X-Received: by 10.152.170.194 with SMTP id ao2mr11760542lac.60.1414591472697; Wed, 29 Oct 2014 07:04:32 -0700 (PDT) Received: from mail-lb0-f170.google.com (mail-lb0-f170.google.com. [209.85.217.170]) by mx.google.com with ESMTPS id n1si7425701lbc.10.2014.10.29.07.04.32 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 29 Oct 2014 07:04:32 -0700 (PDT) Received-SPF: pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.217.170 as permitted sender) client-ip=209.85.217.170; Received: by mail-lb0-f170.google.com with SMTP id 10so2536525lbg.29 for ; Wed, 29 Oct 2014 07:04:32 -0700 (PDT) X-Received: by 10.112.130.41 with SMTP id ob9mr11420377lbb.74.1414591472565; Wed, 29 Oct 2014 07:04:32 -0700 (PDT) X-Forwarded-To: patchwork-forward@linaro.org X-Forwarded-For: patch@linaro.org patchwork-forward@linaro.org Delivered-To: patch@linaro.org Received: by 10.112.84.229 with SMTP id c5csp663027lbz; Wed, 29 Oct 2014 07:04:31 -0700 (PDT) X-Received: by 10.70.109.169 with SMTP id ht9mr2272703pdb.152.1414591470905; Wed, 29 Oct 2014 07:04:30 -0700 (PDT) Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id tf10si4053754pab.175.2014.10.29.07.04.30 for ; Wed, 29 Oct 2014 07:04:30 -0700 (PDT) Received-SPF: none (google.com: linux-gpio-owner@vger.kernel.org does not designate permitted sender hosts) client-ip=209.132.180.67; Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932906AbaJ2OE3 (ORCPT ); Wed, 29 Oct 2014 10:04:29 -0400 Received: from mail-gw1-out.broadcom.com ([216.31.210.62]:22117 "EHLO mail-gw1-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932768AbaJ2OE3 (ORCPT ); Wed, 29 Oct 2014 10:04:29 -0400 X-IronPort-AV: E=Sophos;i="5.04,810,1406617200"; d="scan'208";a="49625695" Received: from irvexchcas07.broadcom.com (HELO IRVEXCHCAS07.corp.ad.broadcom.com) ([10.9.208.55]) by mail-gw1-out.broadcom.com with ESMTP; 29 Oct 2014 08:31:03 -0700 Received: from IRVEXCHSMTP3.corp.ad.broadcom.com (10.9.207.53) by IRVEXCHCAS07.corp.ad.broadcom.com (10.9.208.55) with Microsoft SMTP Server (TLS) id 14.3.174.1; Wed, 29 Oct 2014 07:04:28 -0700 Received: from mail-irva-13.broadcom.com (10.10.10.20) by IRVEXCHSMTP3.corp.ad.broadcom.com (10.9.207.53) with Microsoft SMTP Server id 14.3.174.1; Wed, 29 Oct 2014 07:04:28 -0700 Received: from linaro.ban.broadcom.com (unknown [10.131.60.135]) by mail-irva-13.broadcom.com (Postfix) with ESMTP id C8EC740FEB; Wed, 29 Oct 2014 07:04:09 -0700 (PDT) From: To: Linus Walleij , Alexandre Courbot , Jonathan Corbet CC: Kamlakant Patel , , Subject: [PATCH 5/5] gpio: document basic mmio gpio library Date: Wed, 29 Oct 2014 19:34:17 +0530 Message-ID: <1414591457-31074-1-git-send-email-kamlakant.patel@linaro.org> X-Mailer: git-send-email 1.9.1 MIME-Version: 1.0 Sender: linux-gpio-owner@vger.kernel.org Precedence: list List-ID: X-Mailing-List: linux-gpio@vger.kernel.org X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: kamlakant.patel@linaro.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.217.170 as permitted sender) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org X-Google-Group-Id: 836684582541 List-Post: , List-Help: , List-Archive: List-Unsubscribe: , From: Kamlakant Patel This is a brief documentation on how to use GPIO Generic library for memory-mapped GPIO controllers. Signed-off-by: Kamlakant Patel --- Documentation/gpio/driver.txt | 50 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt index 31e0b5d..563abea 100644 --- a/Documentation/gpio/driver.txt +++ b/Documentation/gpio/driver.txt @@ -190,3 +190,53 @@ gpiochip_free_own_desc(). These functions must be used with care since they do not affect module use count. Do not use the functions to request gpio descriptors not owned by the calling driver. + + +Generic driver for memory-mapped GPIO controllers +------------------------------------------------- +The GPIO generic library provides support for basic platform_device +memory-mapped GPIO controllers, which can be accessed by selecting Kconfig +symbol GPIO_GENERIC and using library functions provided by GPIO generic +driver (see drivers/gpio/gpio-generic.c). +The simplest form of a GPIO controller that the driver support is just a +single "data" register, where GPIO state can be read and/or written. + +The driver can be registered using "basic-mmio-gpio" or for big-endian +notation support use "basic-mmio-gpio-be". The code will configure gpio_chip +and issue gpiochip_add(). + +The driver supports: +- 8/16/32/64 bits registers. The number of GPIOs is determined by the width of + the registers. +- GPIO controllers with clear/set registers. +- GPIO controllers with a single "data" register. +- Big endian bits/GPIOs ordering. + +For setting GPIO's there are three supported configurations: +- single input/output register resource (named "dat"). +- set/clear pair (named "set" and "clr"). +- single output register resource and single input resource ("set" and dat"). + +For setting the GPIO direction, there are three supported configurations: +- simple bidirection GPIO that requires no configuration. +- an output direction register (named "dirout") where a 1 bit indicates the + GPIO is an output. +- an input direction register (named "dirin") where a 1 bit indicates the GPIO + is an input. + +It is possible to use only parts of GPIO generic library. Each GPIO controller +using GPIO generic library needs to include the following header. + + #include + +Use bgpio_init to configure gpio_chip and bgpio_remove to remove the controller. +int bgpio_init(struct bgpio_chip *bgc, struct device *dev, + unsigned long sz, void __iomem *dat, void __iomem *set, + void __iomem *clr, void __iomem *dirout, void __iomem *dirin, + unsigned long flags); + +The "flag" parameter can be following depending on controller configuration: +BGPIOF_BIG_ENDIAN BIT(0) +BGPIOF_UNREADABLE_REG_SET BIT(1) /* reg_set is unreadable */ +BGPIOF_UNREADABLE_REG_DIR BIT(2) /* reg_dir is unreadable */ +BGPIOF_BIG_ENDIAN_BYTE_ORDER BIT(3)