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 AD34FC83000 for ; Tue, 28 Apr 2020 12:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 819CB206D7 for ; Tue, 28 Apr 2020 12:38:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Xpl4XiVD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726787AbgD1MiC (ORCPT ); Tue, 28 Apr 2020 08:38:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726361AbgD1MiC (ORCPT ); Tue, 28 Apr 2020 08:38:02 -0400 Received: from mail-lj1-x241.google.com (mail-lj1-x241.google.com [IPv6:2a00:1450:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF8BEC03C1A9; Tue, 28 Apr 2020 05:38:01 -0700 (PDT) Received: by mail-lj1-x241.google.com with SMTP id f11so16693093ljp.1; Tue, 28 Apr 2020 05:38:01 -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=jaKR5R1WloABoOCNDwha2qUKSeGPIsf61ojAQBzgC2k=; b=Xpl4XiVD8uN3HZPXJDUEvWlNUFkg/wbeIjrtTvd71Okm+zIpEkiPP6pNr77DaV27/E yDY4TpEKX5TkZwNky5GupxcmC8CWmiKkmFD8m+2PFYpHy5HW7fdyMhNyb/H1geqGYqJE e34Ob3ju+51tEYinnRHFQke4dpW6FgqQsZzd+7PMTh5cwlWTrAKCdZ7mPc/LmqTXMMKB CRw3BJoMmiJd+lKPJD/HA/rIMVOoejIa+huOj04X66XtTTL8vuBv3K1XkRTsm8AMX6vm z2UP0xFk4VybbvAcqg/9xr3+xWfIIJby3+mfTnMXxVz6oERYVMGLHAOtNT1IqbyiQ5GO pySw== 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=jaKR5R1WloABoOCNDwha2qUKSeGPIsf61ojAQBzgC2k=; b=aqmSTGXSaWToyDgmqn5pcu1UWnjwkkORg8IdIDZEBB/STbTWNcLLngtsr01I5F7SFy dfp04lRBSzzWvDlu54LZlvmR+sh4yRqenKu5K32DPpHvFOKyz1VkbSo0h6zjRjBmL+m+ CB67sjCod6dVqjkWu3YzWws4EWLYpXE9M2lSzXibg5S+HLQezyHnucd3xyRG+cOD9zk1 P8QSIVRc/TDjhkWE1JyIOervM4PtrGLX4rrKOCVR8/AwdFXKea4VRCtQLmSLfPliyFMU 5bEgVu/8vhHeb/V2QrYLxHmPdJ0xIsUom2C7gRIqiVKeUARhpDwBpnTBZocZrdSTEAh2 NGPA== X-Gm-Message-State: AGi0PuaOdtVDxZD+Pv79abD3YzbONwwiFFuHbLMxmoexgyJiLRB7YCVK o7Q5Ai8TQWH+U4hu5wrJJluMid+D X-Google-Smtp-Source: APiQypIxVhNpDjp5Qg6Ip7K3vj0YXm4hcVNu1KOU3k8f4RfTGbv1CDxkze+vzXhlexo8u+RHlgWgiw== X-Received: by 2002:a2e:b4a5:: with SMTP id q5mr18023098ljm.58.1588077479868; Tue, 28 Apr 2020 05:37:59 -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 w29sm2388095lfq.35.2020.04.28.05.37.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Apr 2020 05:37:59 -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> <4981d7eb-b41e-c597-04ff-3d3295804d5a@nvidia.com> From: Dmitry Osipenko Message-ID: Date: Tue, 28 Apr 2020 15:37:57 +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: <4981d7eb-b41e-c597-04ff-3d3295804d5a@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 28.04.2020 11:01, Jon Hunter пишет: > > On 27/04/2020 16:18, Dmitry Osipenko wrote: >> 27.04.2020 18:12, Thierry Reding пишет: >>> On Mon, Apr 27, 2020 at 05:21:30PM +0300, Dmitry Osipenko wrote: >>>> 27.04.2020 14:00, Thierry Reding пишет: >>>>> On Mon, Apr 27, 2020 at 12:52:10PM +0300, Dmitry Osipenko wrote: >>>>>> 27.04.2020 10:48, Thierry Reding пишет: >>>>>> ... >>>>>>>> Maybe but all these other problems appear to have existed for sometime >>>>>>>> now. We need to fix all, but for the moment we need to figure out what's >>>>>>>> best for v5.7. >>>>>>> >>>>>>> To me it doesn't sound like we have a good handle on what exactly is >>>>>>> going on here and we're mostly just poking around. >>>>>>> >>>>>>> And even if things weren't working quite properly before, it sounds to >>>>>>> me like this patch actually made things worse. >>>>>> >>>>>> There is a plenty of time to work on the proper fix now. To me it sounds >>>>>> like you're giving up on fixing the root of the problem, sorry. >>>>> >>>>> We're at -rc3 now and I haven't seen any promising progress in the last >>>>> week. All the while suspend/resume is now broken on at least one board >>>>> and that may end up hiding any other issues that could creep in in the >>>>> meantime. >>>>> >>>>> Furthermore we seem to have a preexisting issue that may very well >>>>> interfere with this patch, so I think the cautious thing is to revert >>>>> for now and then fix the original issue first. We can always come back >>>>> to this once everything is back to normal. >>>>> >>>>> Also, people are now looking at backporting this to v5.6. Unless we >>>>> revert this from v5.7 it may get picked up for backports to other >>>>> kernels and then I have to notify stable kernel maintainers that they >>>>> shouldn't and they have to back things out again. That's going to cause >>>>> a lot of wasted time for a lot of people. >>>>> >>>>> So, sorry, I disagree. I don't think we have "plenty of time". >>>> >>>> There is about a month now before the 5.7 release. It's a bit too early >>>> to start the panic, IMO :) >>> >>> There's no panic. A patch got merged and it broken something, so we >>> revert it and try again. It's very much standard procedure. >>> >>>> Jon already proposed a reasonable simple solution: to keep PCIe >>>> regulators always-ON. In a longer run we may want to have I2C atomic >>>> transfers supported for a late suspend phase. >>> >>> That's not really a solution, though, is it? It's just papering over >>> an issue that this patch introduced or uncovered. I'm much more in >>> favour of fixing problems at the root rather than keep papering over >>> until we loose track of what the actual problems are. >> >> 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. > > > There are a few issues here, but the issue Thierry and I are referring > to is the regression introduced by this change. Yes this exposes other > problems, but we first need to understand why this breaks resume in > general, regardless of what the PCIe driver is doing. I will look at > this a bit more later this week. Let's postpone the reverting by 1-3 weeks then. Likely that there will be a proper (and trivial) solution by that time, otherwise it should be okay to revert the I2C patch.