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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 5B606C49EAB for ; Fri, 25 Jun 2021 08:06:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43B6060FF4 for ; Fri, 25 Jun 2021 08:06:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230025AbhFYIIU convert rfc822-to-8bit (ORCPT ); Fri, 25 Jun 2021 04:08:20 -0400 Received: from hostingweb31-40.netsons.net ([89.40.174.40]:33479 "EHLO hostingweb31-40.netsons.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229799AbhFYIIQ (ORCPT ); Fri, 25 Jun 2021 04:08:16 -0400 Received: from [77.244.183.192] (port=64446 helo=[192.168.178.41]) by hostingweb31.netsons.net with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1lwgqY-000EWi-K3; Fri, 25 Jun 2021 10:05:54 +0200 Subject: Re: [PATCH v2] PCI: dra7xx: Fix reset behaviour To: Linus Walleij , =?UTF-8?Q?Pali_Roh=c3=a1r?= , Bartosz Golaszewski Cc: Kishon Vijay Abraham I , Lorenzo Pieralisi , linux-pci , Linux-OMAP , Linux ARM , linux-kernel , Rob Herring , Bjorn Helgaas , "open list:GPIO SUBSYSTEM" References: <20210622115604.GA25503@lpieralisi> <20210622121649.ouiaecdvwutgdyy5@pali> <18a104a9-2cb8-7535-a5b2-f5f049adff47@lucaceresoli.net> <4d4c0d4d-41b4-4756-5189-bffa15f88406@ti.com> <20210622205220.ypu22tuxhpdn2jwz@pali> <2873969e-ac56-a41f-0cc9-38e387542aa1@lucaceresoli.net> <20210622211901.ikulpy32d6qlr4yw@pali> <588741e4-b085-8ae2-3311-27037c040a57@lucaceresoli.net> <20210622222328.3lfgkrhsdy6izedv@pali> <20210624233448.ouvczfbogmtnbrye@pali> From: Luca Ceresoli Message-ID: <20966897-c2c9-92e2-c73e-78e0e8acc13d@lucaceresoli.net> Date: Fri, 25 Jun 2021 10:05:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8BIT X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - hostingweb31.netsons.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lucaceresoli.net X-Get-Message-Sender-Via: hostingweb31.netsons.net: authenticated_id: luca@lucaceresoli.net X-Authenticated-Sender: hostingweb31.netsons.net: luca@lucaceresoli.net X-Source: X-Source-Args: X-Source-Dir: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 25/06/21 02:09, Linus Walleij wrote: > On Fri, Jun 25, 2021 at 1:34 AM Pali Rohár wrote: > >>> gpiod_set_value(gpiod, 1) == assert the line >>> gpiod_set_value(gpiod, 0) == de-assert the line >> >> Problem is that some pci controller drivers (e.g. pci-j721e.c or >> pcie-rockchip-host.c) expects that gpiod_set_value_cansleep(gpiod, 1) >> de-asserts the line and it is already used in this way. >> >> Which is opposite of the behavior which you wrote above. > > I sketched a way out of the problem using a quirk in > gpiolib in another response. We have a few of these > cases where we have to code our way out of mistakes, > such things happen. > > The problem is common, and due to the fact that device tree > authors ignores the flag GPIO_ACTIVE_HIGH (which has > been around since the early days of device tree on PowerPC) > instead they opt to do the inversion in code. Which violates the > contract that the DT should describe the hardware. > > The ambition of the DT specifications/schemas are to be operating > system independent, and this kind of stuff creates a situation > where other operating systems can't use the specification without > also going and looking at how Linux has implemented stuff. > Which is against the ambition of the device tree work. > >> I would suggest to define enum/macro with word ASSERT and DEASSERT in >> its name instead of just true/false boolean or 0/1 int. >> >> In case of this PERST# misunderstanding, having assert/deassert in name >> should really help. > > Hm that looks useful, Bart &co what do you think? > > #define GPIOD_ASSERTED 1 > #define GPIOD_DEASSERTED 0 > > in consumer.h, would that be helpful for users? Looks like a good idea to me. It would help making people aware that gpiod_set_value() & co do _not_ take a physical line value. It's done that way since ages, it's documented, yet many developers are still unaware of that... -- Luca