On 06/17/2014 02:07 PM, Bjorn Helgaas wrote:
On Tue, Jun 17, 2014 at 1:27 PM, Myron Stowe <myron.stowe@xxxxxxxxxx> 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@xxxxxxxxxx>
---
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@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
