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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 04B4CC432C0 for ; Wed, 20 Nov 2019 13:50:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0EB3224FC for ; Wed, 20 Nov 2019 13:50:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="BzRe+u7s" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729803AbfKTNuH (ORCPT ); Wed, 20 Nov 2019 08:50:07 -0500 Received: from lelv0143.ext.ti.com ([198.47.23.248]:37242 "EHLO lelv0143.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729591AbfKTNuG (ORCPT ); Wed, 20 Nov 2019 08:50:06 -0500 Received: from lelv0265.itg.ti.com ([10.180.67.224]) by lelv0143.ext.ti.com (8.15.2/8.15.2) with ESMTP id xAKDntNk044995; Wed, 20 Nov 2019 07:49:55 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1574257795; bh=igM4FKkHdrSc7hws60TYIUKdxK6fHbvh4VrbAU0B0qg=; h=Subject:From:To:CC:References:Date:In-Reply-To; b=BzRe+u7s+vnkppJrguEj85EG3WqE4wAKog+ctPf92slMETrjH8ejv45M7RgYClLnm 7+/Rkl5lJ+HUltj2xwbh3Ab+rpZjsbgtw8449hJwH5uxI85vrAmog7ky2FCKxWw9UC ylaQ2L3yk5qERQhTz/l0oCKpl5MADxkRn5VJ5Q6c= Received: from DFLE103.ent.ti.com (dfle103.ent.ti.com [10.64.6.24]) by lelv0265.itg.ti.com (8.15.2/8.15.2) with ESMTPS id xAKDntBN009270 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 20 Nov 2019 07:49:55 -0600 Received: from DFLE103.ent.ti.com (10.64.6.24) by DFLE103.ent.ti.com (10.64.6.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1847.3; Wed, 20 Nov 2019 07:49:54 -0600 Received: from lelv0326.itg.ti.com (10.180.67.84) by DFLE103.ent.ti.com (10.64.6.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1847.3 via Frontend Transport; Wed, 20 Nov 2019 07:49:54 -0600 Received: from [192.168.2.6] (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0326.itg.ti.com (8.15.2/8.15.2) with ESMTP id xAKDnpEt093218; Wed, 20 Nov 2019 07:49:52 -0600 Subject: Re: [RFC 0/2] gpiolib: Initial, basic support for shared GPIO lines From: Peter Ujfalusi To: , , CC: , , , , , , References: <20191120133409.9217-1-peter.ujfalusi@ti.com> Message-ID: <4c7eeb1c-12b6-9073-3755-8ce1ffc803e4@ti.com> Date: Wed, 20 Nov 2019 15:49:51 +0200 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: <20191120133409.9217-1-peter.ujfalusi@ti.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi, On 20/11/2019 15.34, Peter Ujfalusi wrote: > Hi, > > The initial support can replace all use of GPIOD_FLAGS_BIT_NONEXCLUSIVE if the > shared GPIO is configured to follow pass through 'strategy' for the shared GPIO > pin. > > I have only implemented DT support. > > With the shared gpio support one can choose between three different strategy for > managing the shared gpio: > refcounted low: Keep the line low as long as there is at least one low > request is registered > refcounted high: Keep the line high as long as there is at least one high > request is registered > pass through: all requests are allowed to go through without refcounting. > > Few shortcomings as of now: > - can not handle different GPIO_ACTIVE_ on the user side, both the root GPIO > (which is shared) and clients must have the same GPIO_ACTIVE_ mode. > We are using common gpio_desc. > Like with GPIOD_FLAGS_BIT_NONEXCLUSIVE > - refcounting counts _all_ 1/0 requests coming from the users of the shared > GPIO. This could cause issues if clients are using the gpiod API in unbalanced > way. > We would need to have separate tracking for each of the clients and agregate > the level they are asking for at any moment. Basically a new gpio-chip on top > of the real gpio pin can solve this. I forgot to add an example for DT. I have this for two pcm3168a codec, their RST pin is connected to tca6416's p0 pin. The codec's RST line is low active, so the gpio-shared is configured to refcounted high to make sure that a codec is not placed in reset when it does not want it. &main_i2c3 { #address-cells = <1>; #size-cells = <0>; audio_exp: gpio@21 { compatible = "ti,tca6416"; reg = <0x21>; gpio-controller; #gpio-cells = <2>; p00 { gpio-shared; gpios = <0 GPIO_ACTIVE_LOW>; output-high; refcounted-high; line-name = "CODEC RESET"; }; }; pcm3168a_a: audio-codec@47 { compatible = "ti,pcm3168a"; reg = <0x47>; #sound-dai-cells = <1>; reset-gpios = <&audio_exp 0 GPIO_ACTIVE_LOW>; }; pcm3168a_b: audio-codec@46 { compatible = "ti,pcm3168a"; reg = <0x46>; #sound-dai-cells = <1>; reset-gpios = <&audio_exp 0 GPIO_ACTIVE_LOW>; }; }; > > Regards, > Peter > --- > Peter Ujfalusi (2): > dt-bindings: gpio: Document shared GPIO line usage > gpiolib: Support for (output only) shared GPIO line > > .../devicetree/bindings/gpio/gpio.txt | 66 +++++++++ > drivers/gpio/gpiolib-of.c | 28 +++- > drivers/gpio/gpiolib.c | 132 ++++++++++++++++-- > drivers/gpio/gpiolib.h | 10 ++ > 4 files changed, 223 insertions(+), 13 deletions(-) > - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. 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