Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932127AbaF3QtS (ORCPT ); Mon, 30 Jun 2014 12:49:18 -0400 Received: from mail-ob0-f172.google.com ([209.85.214.172]:43609 "EHLO mail-ob0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754754AbaF3QtO (ORCPT ); Mon, 30 Jun 2014 12:49:14 -0400 MIME-Version: 1.0 In-Reply-To: References: <20140617192734.30783.71260.stgit@amt.stowe> Date: Mon, 30 Jun 2014 10:49:13 -0600 Message-ID: Subject: Re: [PATCH] PCI: pciehp: Include the Data Link Layer State Changed bit when clearing the Slot Status register's event bits From: Myron Stowe To: Bjorn Helgaas Cc: Myron Stowe , "linux-pci@vger.kernel.org" , Kenji Kaneshige , "linux-kernel@vger.kernel.org" , 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 On Tue, Jun 17, 2014 at 3:07 PM, Bjorn Helgaas wrote: > On Tue, Jun 17, 2014 at 1:27 PM, Myron Stowe wrote: >> During PCIe hot-plug initialization - pciehp_probe - data structures >> related to slot capabilities are set up. As part of this set up, ISRs are >> put in place to handle slot events and all event bits are cleared out. >> >> This patch adds the Data Link Layer State Changed (PCI_EXP_SLTSTA_DLLSC) >> Slot Status bit to the event bits that are cleared out during >> initialization. > > I think this is related to e48f1b67f668 ("PCI: pciehp: Use link change > notifications for hot-plug and removal"). Prior to that, pcie_isr() > didn't look at the PCI_EXP_SLTSTA_DLLSC bit. > > Apparently there's a non-public report of spurious messages like this > at boot-time, with no actual hotplug events: > > pciehp 0000:82:04.0:pcie24: slot(4): Link Up event > pciehp 0000:82:04.0:pcie24: Device 0000:83:00.0 already exists at > 0000:83:00, cannot hot-add > pciehp 0000:82:04.0:pcie24: Cannot add device at 0000:83:00 > > Device 0000:83:00.0 was enumerated previously, during the normal PCI > device enumeration. I suspect DLLSC was set by the hardware when the > link came up after power-on, and it remained set until Linux booted. > Then when we take the first pciehp interrupt, we notice DLLSC is set > and think it's a new link state change. > > This might be system-specific, because some BIOSes might clear DLLSC > before handing off to the OS. Or my theory might be all wet. > > But I think we should clear DLLSC in any case. We clear all the other > RW1C bits in Slot Status, and I think we should clear DLLSC as well. > > I'd like to include a bugzilla or mailing list reference for the > spurious message, and I'd also like confirmation that this changes > actually fixes it. I just got confirmation from the reporter that the patch fixes the issue they were encountering. I've also asked them numerous time if I could make the bug public as I expect others may be hitting it and could benefit from a BZ and analysis/explanation. I just repeated my request - if they reply positively I'll follow through with some documentation. Myron > > Bjorn > >> Reference: >> PCI-SIG. PCI Express Base Specification Revision 4.0 Version 0.3 >> (PCI-SIG, 2014): 7.8.11. Slot Status Register (Offset 1Ah). >> >> Signed-off-by: Myron Stowe >> --- >> >> drivers/pci/hotplug/pciehp_hpc.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c >> index 42914e0..0568416 100644 >> --- a/drivers/pci/hotplug/pciehp_hpc.c >> +++ b/drivers/pci/hotplug/pciehp_hpc.c >> @@ -794,7 +794,7 @@ struct controller *pcie_init(struct pcie_device *dev) >> pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, >> PCI_EXP_SLTSTA_ABP | PCI_EXP_SLTSTA_PFD | >> PCI_EXP_SLTSTA_MRLSC | PCI_EXP_SLTSTA_PDC | >> - PCI_EXP_SLTSTA_CC); >> + PCI_EXP_SLTSTA_CC | PCI_EXP_SLTSTA_DLLSC); >> >> /* Disable software notification */ >> pcie_disable_notification(ctrl); >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/