From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy for a long time Date: Wed, 29 Apr 2020 17:46:46 +0300 Message-ID: <5863e364-480e-7839-c42b-73a7f6990a30@gmail.com> References: <79f6560e-dbb5-0ae1-49f8-cf1cd95396ec@nvidia.com> <20200427074837.GC3451400@ulmo> <20200427110033.GC3464906@ulmo> <3a06811c-02dc-ce72-ebef-78c3fc3f4f7c@gmail.com> <20200427151234.GE3464906@ulmo> <1ab276cf-c2b0-e085-49d8-b8ce3dba8fbe@gmail.com> <20200429081448.GA2345465@ulmo> <20200429085502.GB2345465@ulmo> <9e36c4ec-ca02-bd15-d765-15635f09db4b@gmail.com> <7442f4cd-6406-41f6-5c9b-932bff8ad5b2@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <7442f4cd-6406-41f6-5c9b-932bff8ad5b2-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Content-Language: en-US Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jon Hunter , Thierry Reding Cc: Wolfram Sang , Laxman Dewangan , Manikanta Maddireddy , Vidya Sagar , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org 29.04.2020 16:57, Jon Hunter пишет: > > On 29/04/2020 13:35, Dmitry Osipenko wrote: >> 29.04.2020 11:55, Thierry Reding пишет: >> ... >>>>> It's not "papering over an issue". The bug can't be fixed properly >>>>> without introducing I2C atomic transfers support for a late suspend >>>>> phase, I don't see any other solutions for now. Stable kernels do not >>>>> support atomic transfers at all, that proper solution won't be backportable. >>>> >>>> Hm... on a hunch I tried something and, lo and behold, it worked. I can >>>> get Cardhu to properly suspend/resume on top of v5.7-rc3 with the >>>> following sequence: >>>> >>>> revert 9f42de8d4ec2 i2c: tegra: Fix suspending in active runtime PM state >>>> apply http://patchwork.ozlabs.org/project/linux-tegra/patch/20191213134417.222720-1-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org/ >>>> >>>> I also ran that through our test farm and I don't see any other issues. >>>> At the time I was already skeptical about pm_runtime_force_suspend() and >>>> pm_runtime_force_resume() and while I'm not fully certain why exactly it >>>> doesn't work, the above on top of v5.7-rc3 seems like a good option. >>>> >>>> I'll try to do some digging if I can find out why exactly force suspend >>>> and resume doesn't work. >>> >>> Ah... so it looks like pm_runtime_force_resume() never actually does >>> anything in this case and then disable_depth remains at 1 and the first >>> tegra_i2c_xfer() will then fail to runtime resume the controller. >> >> That's the exactly expected behaviour of the RPM force suspend/resume. >> The only unexpected part for me is that the tegra_i2c_xfer() runtime >> resume then fails in the NOIRQ phase. > > From reading the changelog for commit 1e2ef05bb8cf ("PM: Limit race > conditions between runtime PM and system sleep (v2))", this is the > expected behaviour for runtime resume in the noirq phase. I'm curious whether there is a way to tell RPM that it's okay to do it for a particular device, like I2C that uses IRQ-safe RPM + doesn't have parent devices that need to be resumed. 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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 2D9A4C83000 for ; Wed, 29 Apr 2020 14:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A9522083B for ; Wed, 29 Apr 2020 14:46:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Haw4PU8y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726974AbgD2Oqv (ORCPT ); Wed, 29 Apr 2020 10:46:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726456AbgD2Oqu (ORCPT ); Wed, 29 Apr 2020 10:46:50 -0400 Received: from mail-lf1-x141.google.com (mail-lf1-x141.google.com [IPv6:2a00:1450:4864:20::141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E1F5C03C1AD; Wed, 29 Apr 2020 07:46:50 -0700 (PDT) Received: by mail-lf1-x141.google.com with SMTP id w14so1475316lfk.3; Wed, 29 Apr 2020 07:46:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=6Iqx43ooxgoOivq+n0TDZ4CBXmi8xKAeuxrrrbvkGzA=; b=Haw4PU8yu6NVYE7MFuT40CZ3zAtmD0g1aiMZvzucctoEE/7fVReA0DnGM0evnNxklX VrPaV3Rel3X5PwawyZrwOI2ZADt9RRF1gmZosRewqRm61ySFMJ3H2LMcudOPmUMg1Cfl 4PfQZD1qvzEB8EyDDEXyky19RxawxmRXsjHXPLQ/82CT8nWQwzYSNc17PnjJYFNsOEBk CyC4NbnO1oj0ozCPd3Gw7mIOeOVsm5vbFapHZrwgO5CbuoR9b8oTGeUROT1Bcjt0kCM1 WVh1icy15qq64apDWa27qcmPzVgopwE+xF7KD4/BwFL+hmjugFOVUDoprHTYKGHt0dzt x6DQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=6Iqx43ooxgoOivq+n0TDZ4CBXmi8xKAeuxrrrbvkGzA=; b=qYubLza8qUGMh65bEBZY0te9Hr0UmqRfqyHHq1KbdFgKfDZ1fJKjLXsdr9suVPXXHX OSRR3Imt5S0u1ZbBj2Jr+/gzEVk10rOzpjYcjCe7MrBUQHX4SkojDjuyzLI/sy1B4Ke5 KutbCItietMcdJ3ZoHc6StPZROuiLD4ftKzsKeiQLuCf5PFARYewKtWMRTVqoDWaw4kM 9fCLgwNPq15F3nCbs1sHA3khIrg/Uhz+l0/esxMbxFIj6tdOOiAWsaOMcRkaTV2Uf5N3 dF4asR3gQmo5jdD2IvUetDbBgGyPu5AL7ByME3yECgcLZIn+QWedAisuct7Sk/+YsZXd NkVw== X-Gm-Message-State: AGi0PuZFBrf/j0C3+i16ogGQuHh3m6TX0KiKGjLSbBAPVK4W7wCnV9a0 jUUMcrN3QMp19jieKE1x3tqj6C4Z X-Google-Smtp-Source: APiQypIXFKXW0+23X9m4XvsDEPOtHxVzRdJkkgu45IxeYCDiHfwes9airQTCiDzijLwznTWJQcOT5A== X-Received: by 2002:a19:2389:: with SMTP id j131mr5921216lfj.116.1588171608227; Wed, 29 Apr 2020 07:46:48 -0700 (PDT) Received: from [192.168.2.145] (ppp91-78-208-152.pppoe.mtu-net.ru. [91.78.208.152]) by smtp.googlemail.com with ESMTPSA id f2sm2428460lja.30.2020.04.29.07.46.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Apr 2020 07:46:47 -0700 (PDT) Subject: Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy for a long time To: Jon Hunter , Thierry Reding Cc: Wolfram Sang , Laxman Dewangan , Manikanta Maddireddy , Vidya Sagar , linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <79f6560e-dbb5-0ae1-49f8-cf1cd95396ec@nvidia.com> <20200427074837.GC3451400@ulmo> <20200427110033.GC3464906@ulmo> <3a06811c-02dc-ce72-ebef-78c3fc3f4f7c@gmail.com> <20200427151234.GE3464906@ulmo> <1ab276cf-c2b0-e085-49d8-b8ce3dba8fbe@gmail.com> <20200429081448.GA2345465@ulmo> <20200429085502.GB2345465@ulmo> <9e36c4ec-ca02-bd15-d765-15635f09db4b@gmail.com> <7442f4cd-6406-41f6-5c9b-932bff8ad5b2@nvidia.com> From: Dmitry Osipenko Message-ID: <5863e364-480e-7839-c42b-73a7f6990a30@gmail.com> Date: Wed, 29 Apr 2020 17:46:46 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <7442f4cd-6406-41f6-5c9b-932bff8ad5b2@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 29.04.2020 16:57, Jon Hunter пишет: > > On 29/04/2020 13:35, Dmitry Osipenko wrote: >> 29.04.2020 11:55, Thierry Reding пишет: >> ... >>>>> It's not "papering over an issue". The bug can't be fixed properly >>>>> without introducing I2C atomic transfers support for a late suspend >>>>> phase, I don't see any other solutions for now. Stable kernels do not >>>>> support atomic transfers at all, that proper solution won't be backportable. >>>> >>>> Hm... on a hunch I tried something and, lo and behold, it worked. I can >>>> get Cardhu to properly suspend/resume on top of v5.7-rc3 with the >>>> following sequence: >>>> >>>> revert 9f42de8d4ec2 i2c: tegra: Fix suspending in active runtime PM state >>>> apply http://patchwork.ozlabs.org/project/linux-tegra/patch/20191213134417.222720-1-thierry.reding@gmail.com/ >>>> >>>> I also ran that through our test farm and I don't see any other issues. >>>> At the time I was already skeptical about pm_runtime_force_suspend() and >>>> pm_runtime_force_resume() and while I'm not fully certain why exactly it >>>> doesn't work, the above on top of v5.7-rc3 seems like a good option. >>>> >>>> I'll try to do some digging if I can find out why exactly force suspend >>>> and resume doesn't work. >>> >>> Ah... so it looks like pm_runtime_force_resume() never actually does >>> anything in this case and then disable_depth remains at 1 and the first >>> tegra_i2c_xfer() will then fail to runtime resume the controller. >> >> That's the exactly expected behaviour of the RPM force suspend/resume. >> The only unexpected part for me is that the tegra_i2c_xfer() runtime >> resume then fails in the NOIRQ phase. > > From reading the changelog for commit 1e2ef05bb8cf ("PM: Limit race > conditions between runtime PM and system sleep (v2))", this is the > expected behaviour for runtime resume in the noirq phase. I'm curious whether there is a way to tell RPM that it's okay to do it for a particular device, like I2C that uses IRQ-safe RPM + doesn't have parent devices that need to be resumed.