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Message-ID: <09d281b2-bba7-0708-9c15-0553d6c49117@huawei.com> Date: Thu, 17 Aug 2023 09:07:07 +0800 From: Yu Liao <liaoyu15@...wei.com> To: Leon Romanovsky <leon@...nel.org> CC: <netdev@...r.kernel.org>, <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>, <liwei391@...wei.com>, Xiongfeng Wang <wangxiongfeng2@...wei.com> Subject: Re: [PATCH net-next] pds_core: remove redundant pci_clear_master() 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
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