Re: [PATCH v4 2/3] PCI/AER: Disable AER interrupt on suspend

[Sathyanarayanan Kuppuswamy]

Hi,

On 4/24/23 10:55 PM, Kai-Heng Feng wrote:
> On Tue, Apr 25, 2023 at 7:47 AM Sathyanarayanan Kuppuswamy
> <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote:
>>
>>
>>
>> On 4/23/23 10:52 PM, Kai-Heng Feng wrote:
>>> PCIe service that shares IRQ with PME may cause spurious wakeup on
>>> system suspend.
>>>
>>> PCIe Base Spec 5.0, section 5.2 "Link State Power Management" states
>>> that TLP and DLLP transmission is disabled for a Link in L2/L3 Ready
>>> (D3hot), L2 (D3cold with aux power) and L3 (D3cold), so we don't lose
>>> much here to disable AER during system suspend.
>>>
>>> This is very similar to previous attempts to suspend AER and DPC [1],
>>> but with a different reason.
>>>
>>> [1] https://lore.kernel.org/linux-pci/20220408153159.106741-1-kai.heng.feng@xxxxxxxxxxxxx/
>>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
>>>
>>> Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
>>> ---
>>
>> IIUC, you encounter AER errors during the suspend/resume process, which
>> results in AER IRQ. Because AER and PME share an IRQ, it is regarded as a
>> spurious wake-up IRQ. So to fix it, you want to disable AER reporting,
>> right?
> 
> Yes. That's exactly what happened.
> 
>>
>> It looks like it is harmless to disable the AER during the suspend/resume
>> path. But, I am wondering why we get these errors? Did you check what errors
>> you get during the suspend/resume path? Are these errors valid?
> 
> I really don't know. I think it's similar to the reasoning in commit
> b07461a8e45b ("PCI/AER: Clear error status registers during
> enumeration and restore"): "AER errors might be recorded when
> powering-on devices. These errors can be ignored, ...".
> For this case, it happens when powering-off the device (D3cold) via
> turning off power resources.

Got it.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

> 
> Kai-Heng
> 
>>
>>
>>>  drivers/pci/pcie/aer.c | 22 ++++++++++++++++++++++
>>>  1 file changed, 22 insertions(+)
>>>
>>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>>> index 1420e1f27105..9c07fdbeb52d 100644
>>> --- a/drivers/pci/pcie/aer.c
>>> +++ b/drivers/pci/pcie/aer.c
>>> @@ -1356,6 +1356,26 @@ static int aer_probe(struct pcie_device *dev)
>>>       return 0;
>>>  }
>>>
>>> +static int aer_suspend(struct pcie_device *dev)
>>> +{
>>> +     struct aer_rpc *rpc = get_service_data(dev);
>>> +     struct pci_dev *pdev = rpc->rpd;
>>> +
>>> +     aer_disable_irq(pdev);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int aer_resume(struct pcie_device *dev)
>>> +{
>>> +     struct aer_rpc *rpc = get_service_data(dev);
>>> +     struct pci_dev *pdev = rpc->rpd;
>>> +
>>> +     aer_enable_irq(pdev);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>>  /**
>>>   * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
>>>   * @dev: pointer to Root Port, RCEC, or RCiEP
>>> @@ -1420,6 +1440,8 @@ static struct pcie_port_service_driver aerdriver = {
>>>       .service        = PCIE_PORT_SERVICE_AER,
>>>
>>>       .probe          = aer_probe,
>>> +     .suspend        = aer_suspend,
>>> +     .resume         = aer_resume,
>>>       .remove         = aer_remove,
>>>  };
>>>
>>
>> --
>> Sathyanarayanan Kuppuswamy
>> Linux Kernel Developer

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer