PCI: pciehp: Clear Data Link Layer State Changed during init

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.

If the BIOS doesn't clear DLLSC before handoff to the OS, pciehp notices
that it's set and interprets it as a new Link Up event, which results in
spurious messages:

  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

Prior to e48f1b67f668 ("PCI: pciehp: Use link change notifications for
hot-plug and removal"), pciehp ignored DLLSC.

Reference:
  PCI-SIG.  PCI Express Base Specification Revision 4.0 Version 0.3
  (PCI-SIG, 2014): 7.8.11. Slot Status Register (Offset 1Ah).

[bhelgaas: add e48f1b67f668 ref and stable tag]
Fixes: e48f1b67f668 ("PCI: pciehp: Use link change notifications for hot-plug and removal")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=79611
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v3.15+

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index f7c370993ab44ec8c71316da6d7fb3460b5b7070..9da84b8b27d8a4cdac4305cde5ac50d203b89583 100644 (file)
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -783,7 +783,7 @@ 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);