[PATCH 3.16 069/125] PCI: pciehp: Clear Data Link Layer State Changed during init

Greg Kroah-Hartman
2014-09-03T23:06:13Z

From: Myron Stowe <myron.stowe@redhat.com>

commit 0d25d35c987d7b0b63368d9c1ae35a917e1a7bab upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/pci/hotplug/pciehp_hpc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -794,7 +794,7 @@ struct controller *pcie_init(struct pcie
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);