Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754050AbaLHGPd (ORCPT ); Mon, 8 Dec 2014 01:15:33 -0500 Received: from mail-pd0-f180.google.com ([209.85.192.180]:56085 "EHLO mail-pd0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751039AbaLHGPc (ORCPT ); Mon, 8 Dec 2014 01:15:32 -0500 MIME-Version: 1.0 Reply-To: rajatxjain@gmail.com In-Reply-To: <546E7120.5080505@gmail.com> References: <546E7120.5080505@gmail.com> Date: Sun, 7 Dec 2014 22:15:31 -0800 Message-ID: Subject: Re: [PATCH v2] PCI: pciehp: Check link state before accessing device during removal From: Rajat Jain To: Bjorn Helgaas , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" Cc: Rajat Jain , Guenter Roeck , Rajat Jain Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Bjorn, Just checking if you got a chance to look at this. Thanks, Rajat On Thu, Nov 20, 2014 at 2:54 PM, Rajat Jain wrote: > While removing a card, we can't assume the presence to mean that the > access to card is OK. That is because the cause of removal may be a > link down event, and the card may still be physically present. Thus, > instead of presence, use the link state to decide whether or not it is > OK to access the card devices. > > Here are the problem symptoms: > During the removal of a card due to link down, sometimes the following > error is seen (because pciehp_unconfigure_device() reads 0xFF from > bridge control register as the link is down, which cause it to assume > that the VGA bit is set): > > pciehp 0000:21:05.0:pcie24: pcie_isr: intr_loc 100 > pciehp 0000:21:05.0:pcie24: Data Link Layer State change > pciehp 0000:21:05.0:pcie24: slot(5): Link Down event > pciehp 0000:21:05.0:pcie24: Disabling domain:bus:device=0000:60:00 > pciehp 0000:21:05.0:pcie24: pciehp_unconfigure_device: domain:bus:dev = 0000:60:00 > pciehp 0000:21:05.0:pcie24: Cannot remove display device 0000:60:00.0 > > Ofcourse, when the link comes back up, the device addition fails too: > > pciehp 0000:21:05.0:pcie24: pcie_isr: intr_loc 100 > pciehp 0000:21:05.0:pcie24: Data Link Layer State change > pciehp 0000:21:05.0:pcie24: pciehp_check_link_active: lnk_status = 6011 > pciehp 0000:21:05.0:pcie24: slot(5): Link Up event > pciehp 0000:21:05.0:pcie24: Enabling domain:bus:device=0000:60:00 > pciehp 0000:21:05.0:pcie24: pciehp_check_link_active: lnk_status = 6011 > pciehp 0000:21:05.0:pcie24: pciehp_check_link_status: lnk_status = 6011 > pciehp 0000:21:05.0:pcie24: Device 0000:60:00.0 already exists at 0000:60:00, cannot hot-add > pciehp 0000:21:05.0:pcie24: Cannot add device at 0000:60:00 > > The problem is not seen with this patch applied. The device removal and > insertion works as expected. > > Signed-off-by: Rajat Jain > Signed-off-by: Rajat Jain > Signed-off-by: Guenter Roeck > --- > v2: Use the already initialized "ctrl" instead of "p_slot->ctrl" > > drivers/pci/hotplug/pciehp_pci.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c > index 9e69403..911f85b 100644 > --- a/drivers/pci/hotplug/pciehp_pci.c > +++ b/drivers/pci/hotplug/pciehp_pci.c > @@ -77,7 +77,7 @@ int pciehp_unconfigure_device(struct slot *p_slot) > { > int rc = 0; > u8 bctl = 0; > - u8 presence = 0; > + bool link_active = false; > struct pci_dev *dev, *temp; > struct pci_bus *parent = p_slot->ctrl->pcie->port->subordinate; > u16 command; > @@ -85,7 +85,7 @@ int pciehp_unconfigure_device(struct slot *p_slot) > > ctrl_dbg(ctrl, "%s: domain:bus:dev = %04x:%02x:00\n", > __func__, pci_domain_nr(parent), parent->number); > - pciehp_get_adapter_status(p_slot, &presence); > + link_active = pciehp_check_link_active(ctrl); > > pci_lock_rescan_remove(); > > @@ -98,7 +98,7 @@ int pciehp_unconfigure_device(struct slot *p_slot) > list_for_each_entry_safe_reverse(dev, temp, &parent->devices, > bus_list) { > pci_dev_get(dev); > - if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE && presence) { > + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE && link_active) { > pci_read_config_byte(dev, PCI_BRIDGE_CONTROL, &bctl); > if (bctl & PCI_BRIDGE_CTL_VGA) { > ctrl_err(ctrl, > @@ -114,7 +114,7 @@ int pciehp_unconfigure_device(struct slot *p_slot) > * Ensure that no new Requests will be generated from > * the device. > */ > - if (presence) { > + if (link_active) { > pci_read_config_word(dev, PCI_COMMAND, &command); > command &= ~(PCI_COMMAND_MASTER | PCI_COMMAND_SERR); > command |= PCI_COMMAND_INTX_DISABLE; > -- > 1.7.9.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/