From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:22169 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758933Ab3BNWRw (ORCPT ); Thu, 14 Feb 2013 17:17:52 -0500 Message-ID: <1360880270.25865.36.camel@ul30vt.home> Subject: Re: [PATCH] pci: Disable slot presence detection around bus reset From: Alex Williamson To: bhelgaas@google.com Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 14 Feb 2013 15:17:50 -0700 In-Reply-To: <20130214183640.16220.33060.stgit@bling.home> References: <20130214183640.16220.33060.stgit@bling.home> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: On Thu, 2013-02-14 at 11:37 -0700, Alex Williamson wrote: > A bus reset can trigger a presence detection change and result in a > suprise hotplug. This is generally not what we want to happen when > trying to reset a device. Disable the presence detection control on > on bridges around bus reset. > > Signed-off-by: Alex Williamson > --- > drivers/pci/pci.c | 29 ++++++++++++++++++++++++----- > 1 file changed, 24 insertions(+), 5 deletions(-) Hmm, this doesn't seem to be sufficient, still seeing it occasionally :-\ > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 5cb5820..c1f7d77 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -3229,8 +3229,8 @@ static int pci_pm_reset(struct pci_dev *dev, int probe) > > static int pci_parent_bus_reset(struct pci_dev *dev, int probe) > { > - u16 ctrl; > - struct pci_dev *pdev; > + u16 ctrl, flags, sltctl = 0; > + struct pci_dev *pdev, *bridge; > > if (pci_is_root_bus(dev->bus) || dev->subordinate || !dev->bus->self) > return -ENOTTY; > @@ -3242,15 +3242,34 @@ static int pci_parent_bus_reset(struct pci_dev *dev, int probe) > if (probe) > return 0; > > - pci_read_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, &ctrl); > + bridge = dev->bus->self; > + > + /* > + * If the parent device supports a slot with presence detection > + * change enabled, holding the bus in reset can trigger that and > + * cause an unwanted surprise removal. Disable presence detection > + * around the bus reset. > + */ > + pcie_capability_read_word(bridge, PCI_EXP_FLAGS, &flags); > + if (flags & PCI_EXP_FLAGS_SLOT) { > + pcie_capability_read_word(bridge, PCI_EXP_SLTCTL, &sltctl); > + if (sltctl & PCI_EXP_SLTCTL_PDCE) > + pcie_capability_write_word(bridge, PCI_EXP_SLTCTL, > + sltctl & ~PCI_EXP_SLTCTL_PDCE); > + } > + > + pci_read_config_word(bridge, PCI_BRIDGE_CONTROL, &ctrl); > ctrl |= PCI_BRIDGE_CTL_BUS_RESET; > - pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl); > + pci_write_config_word(bridge, PCI_BRIDGE_CONTROL, ctrl); > msleep(100); > > ctrl &= ~PCI_BRIDGE_CTL_BUS_RESET; > - pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl); > + pci_write_config_word(bridge, PCI_BRIDGE_CONTROL, ctrl); > msleep(100); > > + if (sltctl & PCI_EXP_SLTCTL_PDCE) > + pcie_capability_write_word(bridge, PCI_EXP_SLTCTL, sltctl); > + > return 0; > } > >