pci_pcie_cap invalid on AER/EEH enabled PPC?

[Jon Mason]

On Tue, Jul 5, 2011 at 10:41 AM, Richard A Lary
<rlary at linux.vnet.ibm.com> wrote:
> On 7/1/2011 1:00 PM, Richard A Lary wrote:
>>
>> On 7/1/2011 12:02 PM, Jon Mason wrote:
>>>
>>> On Fri, Jul 1, 2011 at 1:30 PM, Richard A Lary<rlary at linux.vnet.ibm.com>
>>> wrote:
>>>>
>>>> On 7/1/2011 8:24 AM, Jon Mason wrote:
>>>>>
>>>>> I recently sent out a number of patches to migrate drivers calling
>>>>> `pci_find_capability(pdef, PCI_CAP_ID_EXP)` to pci_pcie_cap. This
>>>>> function takes uses a PCI-E capability offset that was determined by
>>>>> calling pci_find_capability during the PCI bus walking. In response
>>>>> to one of the patches, James Smart posted:
>>>>>
>>>>> "The reason is due to an issue on PPC platforms whereby use of
>>>>> "pdev->is_pcie" and pci_is_pcie() will erroneously fail under some
>>>>> conditions, but explicit search for the capability struct via
>>>>> pci_find_capability() is always successful. I expect this to be due
>>>>> a shadowing of pci config space in the hal/platform that isn't
>>>>> sufficiently built up. We detected this issue while testing AER/EEH,
>>>>> and are functional only if the pci_find_capability() option is used."
>>>>>
>>>>> See http://marc.info/?l=linux-scsi&m=130946649427828&w=2 for the whole
>>>>> post.
>>>>>
>>>>> Based on his description above pci_pcie_cap
>>>>> andpci_find_capability(pdef, PCI_CAP_ID_EXP) should be functionally
>>>>> equivalent. If this is not safe, then the PCI bus walking code is
>>>>> most likely busted on EEH enabled PPC systems (and that is a BIG
>>>>> problem). Can anyone confirm this is still an issue?
>>>>
>>>> Jon,
>>>>
>>>> I applied the following debug patch to lpfc driver in a 2.6.32 distro
>>>> kernel ( I had this one handy, I can try with mainline later today )
>>>>
>>>> ---
>>>> drivers/scsi/lpfc/lpfc_init.c | 10 10 + 0 - 0 !
>>>> 1 file changed, 10 insertions(+)
>>>>
>>>> Index: b/drivers/scsi/lpfc/lpfc_init.c
>>>> ===================================================================
>>>> --- a/drivers/scsi/lpfc/lpfc_init.c
>>>> +++ b/drivers/scsi/lpfc/lpfc_init.c
>>>> @@ -3958,6 +3958,16 @@ lpfc_enable_pci_dev(struct lpfc_hba *phb
>>>> pci_try_set_mwi(pdev);
>>>> pci_save_state(pdev);
>>>>
>>>> + printk(KERN_WARNING "pcicap: is_pcie=%x pci_cap=%x pcie_type=%x\n",
>>>> + pdev->is_pcie,
>>>> + pdev->pcie_cap,
>>>> + pdev->pcie_type);
>>>> +
>>>> + if (pci_is_pcie(pdev))
>>>> + printk(KERN_WARNING "pcicap: true\n");
>>>> + else
>>>> + printk(KERN_WARNING "pcicap: false\n");
>>>> +
>>>> /* PCIe EEH recovery on powerpc platforms needs fundamental reset */
>>>> if (pci_find_capability(pdev, PCI_CAP_ID_EXP))
>>>> pdev->needs_freset = 1;
>>>>
>>>> This is output upon driver load on an IBM Power 7 model 8233-E8B server.
>>>>
>>>> dmesg | grep pcicap
>>>> Linux version 2.6.32.42-pcicap-ppc64 (geeko at buildhost) (gcc version
>>>> 4.3.4
>>>> [gcc-4_3-branch revision 152973] (SUSE Linux) ) #1 SMP Fri Jul 1
>>>> 09:31:27
>>>> PDT 2011
>>>> pcicap: is_pcie=0 pci_cap=0 pcie_type=0
>>>> pcicap: false
>>>> pcicap: is_pcie=0 pci_cap=0 pcie_type=0
>>>> pcicap: false
>>>> pcicap: is_pcie=0 pci_cap=0 pcie_type=0
>>>> pcicap: false
>>>> pcicap: is_pcie=0 pci_cap=0 pcie_type=0
>>>> pcicap: false
>>>>
>>>> It would appear that the pcie information is not set in pci_dev
>>>> structure
>>>> for
>>>> this device at the time the driver is being initialized during boot.
>>>
>>> Thanks for trying this. Can you confirm that the other devices in the
>>> system have this issue as well (or show that it is isolated to the lpr
>>> device)? You can add printks in set_pcie_port_type() to verify what
>>> is being set on bus walking and to see when it is being called with
>>> respect to when it is being populated by firmware.
>>
>> Jon,
>>
>> I will give this suggestion a try and post results
>
> On Power PC platforms, set_pcie_port_type() is not called.  On Power PC,
> pci_dev structure is initialized by of_create_pci_dev().  However, the
> structure member pcie_cap is NOT computed nor set in this function.

Yes, it is.  of_create_pci_dev() calls set_pcie_port_type()
http://lxr.linux.no/linux+v2.6.39/arch/powerpc/kernel/pci_of_scan.c#L144

That function sets pdev->pcie_cap
http://lxr.linux.no/linux+v2.6.39/drivers/pci/probe.c#L896

So, it should be set.  It looks like there is a bug in
of_create_pci_dev, as set_pcie_port_type is being called BEFORE the
BARs are setup.  If you move set_pcie_port_type prior to
pci_device_add (perhaps even after), then I bet the issue is resolved.

Thanks,
Jon

> The information used to populate pci_dev comes from the Power PC
> device_tree passed to the OS by Open Firmware.
>
> Based upon standing Power PC design, we cannot support patches
> which replace pci_find_capability(pdef, PCI_CAP_ID_EXP) with
> pci_is_pcie(pdev) on Power PC platforms.
>
> -rich
>
>