linux-kernel - Re: [PATCH pci-next] pci/edr: Ignore Surprise Down error on hot removal

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Date: Mon, 4 Mar 2024 11:33:52 -0800
From: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To: Lukas Wunner <lukas@...ner.de>, Ethan Zhao <haifeng.zhao@...ux.intel.com>
Cc: bhelgaas@...gle.com, ilpo.jarvinen@...ux.intel.com,
 sathyanarayanan.kuppuswamy@...ux.intel.com, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, kbusch@...nel.org
Subject: Re: [PATCH pci-next] pci/edr: Ignore Surprise Down error on hot
 removal

Hi Ethan,

On 3/4/2024 3:58 AM, Lukas Wunner wrote:
> On Mon, Mar 04, 2024 at 04:08:19AM -0500, Ethan Zhao wrote:
>> Per PCI firmware spec r3.3 sec 4.6.12, for firmware first mode DPC
>> handling path, FW should clear UC errors logged by port and bring link
>> out of DPC, but because of ambiguity of wording in the spec, some BIOSes
>> doesn't clear the surprise down error and the error bits in pci status,
>> still notify OS to handle it. thus following trick is needed in EDR when
>> double reporting (hot removal interrupt && dpc notification) is hit.

Please correct me if I'm wrong.

When there is double reporting (hot removal interrupt && dpc 
notification), won't the DPC handler be called always which takes care 
of clearing the surprise down errors? Do we need it again from EDR handler?

Thanks
Smita

> 
> Please provide more detailed information about the hardware and BIOS
> affected by this.
> 
> 
>> -static void dpc_handle_surprise_removal(struct pci_dev *pdev)
>> +bool  dpc_handle_surprise_removal(struct pci_dev *pdev)
>>   {
>> +	if (!dpc_is_surprise_removal(pdev))
>> +		return false;
> 
> This change of moving dpc_is_surprise_removal() into
> dpc_handle_surprise_removal() seems unrelated to the problem at hand.
> 
> Please drop it if it's unnecessary to fix the issue.
> 
> 
>> --- a/drivers/pci/pcie/edr.c
>> +++ b/drivers/pci/pcie/edr.c
>> @@ -184,6 +184,9 @@ static void edr_handle_event(acpi_handle handle, u32 event, void *data)
>>   		goto send_ost;
>>   	}
>>   
>> +	if (dpc_handle_surprise_removal(edev))
>> +		goto send_ost;
>> +
>>   	dpc_process_error(edev);
>>   	pci_aer_raw_clear_status(edev);
> 
> This seems to be the only necessary change.  Please reduce the
> patch to contain only it and no other refactoring.
> 
> Please capitalize the "PCI/EDR: " prefix in the subject and add
> a Fixes tag.
> 
> Thanks,
> 
> Lukas
>