Messages in this thread | | | Date | Tue, 17 Jun 2014 15:55:31 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH] PCI: pciehp: Include the Data Link Layer State Changed bit when clearing the Slot Status register's event bits |
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On 06/17/2014 02:07 PM, Bjorn Helgaas wrote: > On Tue, Jun 17, 2014 at 1:27 PM, Myron Stowe <myron.stowe@redhat.com> 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 >
I think I have seen that message once in a while in our systems. Rajat, didn't we talk about this a while ago ?
Guenter
> 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 <myron.stowe@redhat.com> >> --- >> >> 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/ > > > >
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