Re: pci-express hotplug

[Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>]

Jens Axboe wrote:
> On Tue, Oct 13 2009, Kenji Kaneshige wrote:
>> Jens Axboe wrote:
>>> Hi,
>>>
>>> I'm trying to get pci-express hotplug working in a box here. I don't
>>> really care about the hotplug aspect, I just want the darn pci-e slots
>>> that are designated hotplug slots to actually WORK. When I load pciehp,
>>> I get:
>>>
>>> Firmware did not grant requested _OSC control
>>> Firmware did not grant requested _OSC control
>>> Firmware did not grant requested _OSC control
>>> Firmware did not grant requested _OSC control
>>> pciehp 0000:00:05.0:pcie04: HPC vendor_id 8086 device_id 340c ss_vid 0 ss_did 0
>>> pciehp 0000:00:05.0:pcie04: service driver pciehp loaded
>>> Firmware did not grant requested _OSC control
>>> pciehp 0000:00:07.0:pcie04: HPC vendor_id 8086 device_id 340e ss_vid 0 ss_did 0
>>> pciehp 0000:00:07.0:pcie04: service driver pciehp loaded
>>> Firmware did not grant requested _OSC control
>>> pciehp 0000:80:07.0:pcie04: HPC vendor_id 8086 device_id 340e ss_vid 0 ss_did 0
>>> pciehp 0000:80:07.0:pcie04: service driver pciehp loaded
>>> pciehp 0000:80:09.0:pcie04: HPC vendor_id 8086 device_id 3410 ss_vid 0 ss_did 0
>>> pciehp 0000:80:09.0:pcie04: service driver pciehp loaded
>>> pciehp: PCI Express Hot Plug Controller Driver version: 0.4
>>>
>>> and the devices in the hotplug slots stay off. Is this an ACPI/bios
>>> issue? How can I debug this?
>>>
>> Could you give me the result of "ls -lR /sys/bus/pci/slots/"
>> after loading pciehp?
> 
> I have attached the result of that ls prior to loading pciehp/acpiphp
> (pre-load), after loading pciehp (pciehp-load), and with acpiphp loaded
> only as well (acpiphp-load).
> 

Thank you for the info. From the information, I confirmed that hotplug
slots are detected by pciehp even though _OSC evaluation failed. There
are two ways to take control from the firmware through ACPI control
method. One is _OSC control method, and the other is OSHP control method.
I guess your ACPI fimware has both _OSC and OSHP on DSDT (ACPI Namespace),
and pciehp assumes that it took control through OSHP after the _OSC
evaluation failure. I think this pciehp's behavior is wrong because of
the following reasons and I think pciehp driver mis-detected the hotplug
slots on your environment because of this.

- According to the PCI firmware specification, pciehp driver must use the
  result of _OSC, if the platform implements both _OSC and OSHP.
- OSHP control method seems only for SHPC, not for PCI Express native hot-
  plug. So pciehp must not evaluate OSHP to take control from firmware.

To confirm this, could you send me the dmesg output after loading pciehp
with 'debug_acpi' of pci_hotplug (PCI hotplug core driver) enabled?
For example,

    $ su
    # echo Y > /sys/module/pci_hotplug/parameters/debug_acpi
    # modprobe pciehp
    # dmesg

And if it is possible, could you send me DSDT of your platform?

Anyway, my recommendation is using acpiphp on your environment because
your firmware didn't grant control over hotplug control through _OSC.
>From the information, acpiphp also detects the hotplug slots successfully.
Please try "echo 1 > /sys/bus/pci/slots/<slot#>/power". It would turn on
the slot and initialize adapter card on the slot.

Thanks,
Kenji Kaneshige