From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v3 3/7] PCI: Do not disable memory decoding in pci_reassigndev_resource_alignment() To: Gavin Shan References: <1467283993-3185-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1467283993-3185-4-git-send-email-xyjxie@linux.vnet.ibm.com> <20160701005036.GA18999@gwshan> Cc: nikunj@linux.vnet.ibm.com, zhong@linux.vnet.ibm.com, linux-doc@vger.kernel.org, aik@ozlabs.ru, linux-pci@vger.kernel.org, corbet@lwn.net, linux-kernel@vger.kernel.org, warrier@linux.vnet.ibm.com, alex.williamson@redhat.com, paulus@samba.org, bhelgaas@google.com, linuxppc-dev@lists.ozlabs.org From: Yongji Xie Date: Fri, 1 Jul 2016 14:35:04 +0800 MIME-Version: 1.0 In-Reply-To: <20160701005036.GA18999@gwshan> Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: Sender: linux-kernel-owner@vger.kernel.org List-ID: Hi Gavin, On 2016/7/1 8:50, Gavin Shan wrote: > On Thu, Jun 30, 2016 at 06:53:09PM +0800, Yongji Xie wrote: >> We should not disable memory decoding when we reassign alignment >> in pci_reassigndev_resource_alignment(). It's meaningless and >> have some side effect. For example, some fixup functions such as >> quirk_e100_interrupt() read PCI_COMMAND_MEMORY to know whether >> the devices has been initialized by the firmware or not. If we >> disable memory decoding here, these functions will get a wrong >> information that the devices was not initialized by the firmware >> which may cause a wrong fixup. Besides, disabling memory decoding >> may also break some devices that need to have memory decoding >> always-on during probing. >> > It seems the changelog isn't correct enough if it's talking about > below check in code: > > if (!(command & PCI_COMMAND_MEMORY) || !pci_resource_start(dev, 0)) > return; Could you give me more details? It seems that we couldn't disable e100 interrupts which enabled by some firmware if we disabling memory decoding here. >> Signed-off-by: Yongji Xie >> --- >> drivers/pci/pci.c | 8 +------- >> 1 file changed, 1 insertion(+), 7 deletions(-) >> >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >> index 6ae02de..6241cfc 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -4820,7 +4820,6 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) >> int i; >> struct resource *r; >> resource_size_t align, size; >> - u16 command; >> >> /* We should never try to reassign VF's alignment */ >> if (dev->is_virtfn) >> @@ -4838,12 +4837,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) >> return; >> } >> >> - dev_info(&dev->dev, >> - "Disabling memory decoding and releasing memory resources.\n"); >> - pci_read_config_word(dev, PCI_COMMAND, &command); >> - command &= ~PCI_COMMAND_MEMORY; >> - pci_write_config_word(dev, PCI_COMMAND, command); >> - >> + dev_info(&dev->dev, "Releasing memory resources.\n"); > Is there a problem you found with PCI_COMMAND removed? If so, could you > please share more details, thanks. Disabling memory decoding may break some devices which have flag mmio_always_on. Besides the mmio_always_on case, I also found this would break some P2P bridge such as PEX 8718 controller. Thanks, Yongji