From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7036E379 for ; Thu, 17 Aug 2023 01:07:12 +0000 (UTC) Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EACB1BE8 for ; Wed, 16 Aug 2023 18:07:10 -0700 (PDT) Received: from dggpeml500003.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4RR6Fh32q2zNmf5; Thu, 17 Aug 2023 09:03:36 +0800 (CST) Received: from [10.174.177.173] (10.174.177.173) by dggpeml500003.china.huawei.com (7.185.36.200) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Thu, 17 Aug 2023 09:07:07 +0800 Message-ID: <09d281b2-bba7-0708-9c15-0553d6c49117@huawei.com> Date: Thu, 17 Aug 2023 09:07:07 +0800 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH net-next] pds_core: remove redundant pci_clear_master() Content-Language: en-US To: Leon Romanovsky CC: , , , , , , Xiongfeng Wang References: <20230816013802.2985145-1-liaoyu15@huawei.com> <20230816063820.GV22185@unreal> <20230816103941.GW22185@unreal> From: Yu Liao In-Reply-To: <20230816103941.GW22185@unreal> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.173] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500003.china.huawei.com (7.185.36.200) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00,HK_RANDOM_ENVFROM, HK_RANDOM_FROM,NICE_REPLY_A,RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On 2023/8/16 18:39, Leon Romanovsky wrote: > On Wed, Aug 16, 2023 at 05:39:33PM +0800, Yu Liao wrote: >> On 2023/8/16 14:38, Leon Romanovsky wrote: >>> On Wed, Aug 16, 2023 at 09:38:02AM +0800, Yu Liao wrote: >>>> pci_disable_device() involves disabling PCI bus-mastering. So remove >>>> redundant pci_clear_master(). >>> >>> I would say that this commit message needs to be more descriptive and >>> explain why pci_disable_device() will actually disable PCI in these >>> flows. >>> >>> According to the doc and code: >>> 2263 * Note we don't actually disable the device until all callers of >>> 2264 * pci_enable_device() have called pci_disable_device(). >>> >>> Thanks >>> >> Thank you for the review. My bad, I didn't describe it clearly in commit >> message. I will send the v2 version and add the following explanation: >> >> do_pci_disable_device() disable PCI bus-mastering as following: >> static void do_pci_disable_device(struct pci_dev *dev) >> { >> u16 pci_command; >> >> pci_read_config_word(dev, PCI_COMMAND, &pci_command); >> if (pci_command & PCI_COMMAND_MASTER) { >> pci_command &= ~PCI_COMMAND_MASTER; >> pci_write_config_word(dev, PCI_COMMAND, pci_command); >> } >> >> pcibios_disable_device(dev); >> } >> And pci_disable_device() sets dev->is_busmaster to 0. >> >> So for pci_dev that has called pci_enable_device(), pci_disable_device() >> involves disabling PCI bus-mastering. Remove redundant pci_clear_master() in >> the following places: >> - In error path 'err_out_clear_master' of pdsc_probe(), pci_enable_device() >> has already been called. >> - In pdsc_remove(), pci_enable_device() has already been called in pdsc_probe(). > > All that you need to add is a sentence that pci_enable_device() is > called only once before calling to pci_disable_device() and such > pci_clear_master() is not needed. > Thank you for the review. I'll make the suggested changes and send the V2. Best regards, Yu > Thanks