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=-4.2 required=3.0 tests=BAYES_00,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 39F00C433E0 for ; Fri, 5 Mar 2021 05:18:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 099FD65005 for ; Fri, 5 Mar 2021 05:18:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229486AbhCEFR6 (ORCPT ); Fri, 5 Mar 2021 00:17:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229528AbhCEFRw (ORCPT ); Fri, 5 Mar 2021 00:17:52 -0500 Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 557A3C061574 for ; Thu, 4 Mar 2021 21:17:49 -0800 (PST) Received: by mail-pl1-x62e.google.com with SMTP id a24so778109plm.11 for ; Thu, 04 Mar 2021 21:17:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=uSrdnkV09lTxG+R7vQpH6L1VvRfYR70ruw7SEzHASnM=; b=ZaPVd5akbCMUMuPKO4M62UBbcP/k0UW2rylGFGwh3yE8fpTsH54uHtz3NGZmkhFlzC WnWfmVJ8zuDKzes6tRevN16C99ak2tr0LQSt5inf98u1aImf1krM8Ra6CdbTm5trjsrd qFbe8Cv2P2lkXnU0uNC/PIAtw+IOwlxp4JzA2QSmzmt4649Rx/tzQ+ubNUh/K8T51cIZ 8NTyzfU9DM+FQKYhrJwVjJpJrj3Oi0E1OGsOcbU4H3wgYGTCaKh4Gq+lyqBCAc6iXZ9e Sk/RzRHQMYnbLFKKDPKENvYmNP/6gL4m/P0Y3dLiP3ctSXSop3uImMhwvnMGT1UjUCzF K8Lg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=uSrdnkV09lTxG+R7vQpH6L1VvRfYR70ruw7SEzHASnM=; b=KPJzz8638DlBj7RfysCk0SGePhU12sAqtjkLoHXfuxiHPhs8+0nuZ2y686OCVwWzFw g6TgwvjmcQLTa3NcEngNXaiD+IlxTukaq+Va6gmtxFeT+/rVM0fFrmh3LOCO04Xgm7RF CY7D8FXGgrAasn1dOL7BrB2lf+/etew4EcygE9br7V89E4wdPj3iGTyNwb+yrLd++AWi XYQ9DMD0884+C6iEBOCMST1tZDUaTZp5XZLNBsn66mmXcRuP6DqR8roPR9ij8eUA94T+ WPQa+EzNqvwobMqahmccnuHMZe6mhskDNw1zBdz1ruiLJ7u7O/oHjWroFJutmzCrsb9k b39w== X-Gm-Message-State: AOAM5330k4xagA4PL4QaD6bNaYPbvxfqpyc12X+iaV3dkewYSqV3TnQq 88eIzbPhhwNiTbWedr8t3AiIzgtml/KDOw== X-Google-Smtp-Source: ABdhPJwE1QSa6JvKxFSr8tuXNoaJxifu7iNzJaUB/YTefI+iwZYytL2LfQ0jOtkXg3HsAZXofpOLyw== X-Received: by 2002:a17:90a:7e94:: with SMTP id j20mr8784615pjl.8.1614921468816; Thu, 04 Mar 2021 21:17:48 -0800 (PST) Received: from localhost ([211.108.35.36]) by smtp.gmail.com with ESMTPSA id 21sm953310pfo.167.2021.03.04.21.17.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Mar 2021 21:17:48 -0800 (PST) Date: Fri, 5 Mar 2021 14:17:46 +0900 From: Minwoo Im To: Bjorn Helgaas Cc: Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , linux-pci@vger.kernel.org Subject: Re: [PATCH] PCI: Take __pci_set_master in do_pci_disable_device Message-ID: <20210305051746.GA4744@localhost.localdomain> References: <20210304044013.GA15757@localhost.localdomain> <20210304121143.GA821086@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210304121143.GA821086@bjorn-Precision-5520> User-Agent: Mutt/1.11.4 (2019-03-13) Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 21-03-04 06:11:43, Bjorn Helgaas wrote: > On Thu, Mar 04, 2021 at 01:40:13PM +0900, Minwoo Im wrote: > > On 21-02-24 23:46:00, Krzysztof Wilczyński wrote: > > > Hi Minwoo, > > > > > > Sorry for a very late reply! > > > > > > [...] > > > > > You might need to improve the subject a little - it should be brief but > > > > > still informative. > > > > > > > > > > > __pci_set_mater() has debug log in there so that it would be better to > > > > > > take this function. So take __pci_set_master() function rather than > > > > > > open coding it. This patch didn't move __pci_set_master() to above to > > > > > > avoid churns. > > > > > [...] > > > > > > > > > > It would be __pci_set_master() in the sentence above. Also, perhaps > > > > > "use" would be better than "take". Generally, this commit message might > > > > > need a little improvement to be more clear why are you do doing this. > > > > > > > > Sure, if we consolidate bus master enable clear functions to a single > > > > one, it would be better to debug and tracing the kernel behaviors. > > > > > > > > Let me describe this 'why' to the description. > > > > > > Sounds great! Thank you! > > > > > > [...] > > > > > You could use pci_clear_master(), which we export and that internally > > > > > calls __pci_set_master(), so there would be no need to add any forward > > > > > declarations or to move anything around in the file. > > > > > > > > Moving delcaration to above might be churn, and I agree with your point. > > > > > > I am sure that when it makes sense, then probably folks would not > > > object, especially since "churn" can be subjective. > > > > > > > > Having said that, there is a difference between do_pci_disable_device() > > > > > and how __pci_set_master() works - the latter sets the is_busmaster flag > > > > > accordingly on the given device whereas the former does not. This might > > > > > be of some significance - not sure if we should or should not set this, > > > > > since the do_pci_disable_device() does not do that (perhaps it's on > > > > > purpose or due to some hisoric reasons). > > > > > > > > Thanks for pointing out this. I think the difference about > > > > `is_busmaster` flag looks like it should not be cleared in case of power > > > > suspend case: > > > > > > > > # Suspend > > > > pci_pm_default_suspend() > > > > pci_disable_enabled_device() > > > > > > > > # Resume > > > > pci_pm_reenable_device() > > > > pci_set_master() <-- This is based on (is_busmaster) > > > > > > > > > > > > Please let me know if I'm missing here, and appreciate pointing that > > > > out. Maybe I can post v2 patch with add an argument of whether > > > > `is_busmaster` shoud be set inside of the function or not to > > > > __pci_set_master()? > > > [...] > > > > > > Nothing is ever simple, isn't it? :-) > > > > > > We definitely need to make sure that PM can keep relying on the > > > is_busmaster flag to restore bus mastering to previous state after the > > > device would resume after being suspended. > > > > Yes, > > > > > If we add another boolean argument, then we would need to update the > > > __pci_set_master() only in two other places, aside of using it in the > > > do_pci_disable_device() function, as per (as of 5.11.1 kernel): > > > > I agree with this approach. I can try it by adding another bool > > argument to decide whether to update the is_busmaster flag or not inside > > of the __pci_set_master. > > > > > > > > File Line Content > > > drivers/pci/pci.c 4308 __pci_set_master(dev, true); > > > drivers/pci/pci.c 4319 __pci_set_master(dev, false); > > > > > > This is not all that terrible, provided that we _really_ do want to > > > change this function signature and then add another condition inside. > > > > > > What do you think? If you still like the idea, then send second version > > > over with all the other proposed changes. > > > > Let me prepare the next version of this patch. Thanks! > > Can you clarify what the purpose of this patch is? Is it to fix a > defect, improve debug output, make the code cleaner, etc? > > The commit log really just describes *what* the patch does, and I'm > looking for the *why*. I should have described why this patch is introdcued. do_pci_disable_device clears the Bus Master Enable bit just like what __pci_set_master does which is kind of duplications. Also, __pci_set_master has debug print log which is useful for users to figure out whether bus master is set or cleared. This patch makes do_pci_disable_device call __pci_set_master to take the debug log advantages and make code cleaner by clearing duplicated codes. > Bjorn