linux-kernel - Re: [PATCH v4 1/3] PCI: pciehp: Add support for async hotplug with native AER and DPC/EDR

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Message-ID: <440ad7c8-35f7-5b15-5de6-f220cae2cde0@amd.com>
Date:   Tue, 12 Sep 2023 15:45:34 -0700
From:   Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: Re: [PATCH v4 1/3] PCI: pciehp: Add support for async hotplug with
 native AER and DPC/EDR

On 8/28/2023 12:35 AM, Lukas Wunner wrote:
> On Tue, Aug 15, 2023 at 09:20:41PM +0000, Smita Koralahalli wrote:
>> According to PCIe r6.0 sec 6.7.6 [1], async removal with DPC may result in
>> surprise down error. This error is expected and is just a side-effect of
>> async remove.
>>
>> Add support to handle the surprise down error generated as a side-effect
>> of async remove. Typically, this error is benign as the pciehp handler
>> invoked by PDC or/and DLLSC alongside DPC, de-enumerates and brings down
>> the device appropriately. But the error messages might confuse users. Get
>> rid of these irritating log messages with a 1s delay while pciehp waits
>> for dpc recovery.
> [...]
>> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> 
> Reviewed-by: Lukas Wunner <lukas@...ner.de>
> 
> The subject is slightly inaccurate as this doesn't touch pciehp source
> files, although it is *related* to pciehp.
> 
> As an example, a perhaps more accurate subject might be something like...
> 
>    PCI/DPC: Ignore Surprise Down errors on hot removal
> 
> ...but I don't think it's necessary to respin just for that as Bjorn is
> probably able to adjust the subject to his liking when applying the patch.
> 
> Thanks a lot for patiently pursuing this issue, good to see it fixed.
> 
> Five years ago there was an attempt to solve it through masking Surprise
> Down errors, which you've verified to not be a viable approach:
> 
> https://patchwork.kernel.org/project/linux-pci/patch/20180818065126.77912-2-okaya@kernel.org/
> 
> Lukas

Thanks for the review. Would it be possible to consider this patch as a 
standalone while I work on 10-bit tags enumeration? I can do v5 for this 
patch with $SUBJECT changes and also include clearing Atomic Ops and 
10-bit tags unconditionally on hot-remove if that works..

Thanks,
Smita