Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965369AbaFQVjK (ORCPT ); Tue, 17 Jun 2014 17:39:10 -0400 Received: from mail-ig0-f182.google.com ([209.85.213.182]:39653 "EHLO mail-ig0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964863AbaFQVjD (ORCPT ); Tue, 17 Jun 2014 17:39:03 -0400 MIME-Version: 1.0 In-Reply-To: <20140617192734.30783.71260.stgit@amt.stowe> References: <20140617192734.30783.71260.stgit@amt.stowe> From: Bjorn Helgaas Date: Tue, 17 Jun 2014 15:07:56 -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 To: Myron Stowe Cc: "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 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. 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-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/