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Date:   Wed, 21 Jun 2023 11:55:08 -0700
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Subject: Re: [PATCH v2 2/2] PCI: pciehp: Clear the optional capabilities in
 DEVCTL2 on a hot-plug
Content-Language: en-US
To:     Lukas Wunner <lukas@wunner.de>
Cc:     linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        Bjorn Helgaas <bhelgaas@google.com>, oohall@gmail.com,
        Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Yazen Ghannam <yazen.ghannam@amd.com>,
        Fontenot Nathan <Nathan.Fontenot@amd.com>
References: <20230418210526.36514-1-Smita.KoralahalliChannabasappa@amd.com>
 <20230418210526.36514-3-Smita.KoralahalliChannabasappa@amd.com>
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 <cc36bb5b-6a4a-258b-6707-4d019154e019@amd.com>
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 <d9cf3451-c0c1-ab86-0528-2c05982e7872@amd.com>
 <20230621071259.GA2028@wunner.de>
From:   Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
In-Reply-To: <20230621071259.GA2028@wunner.de>
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On 6/21/2023 12:12 AM, Lukas Wunner wrote:
> On Fri, Jun 16, 2023 at 04:34:27PM -0700, Smita Koralahalli wrote:
>> On 6/16/2023 11:24 AM, Lukas Wunner wrote:
>>> On Mon, May 22, 2023 at 03:23:31PM -0700, Smita Koralahalli wrote:
>>>> On 5/11/2023 4:19 AM, Lukas Wunner wrote:
>>>>> On Tue, Apr 18, 2023 at 09:05:26PM +0000, Smita Koralahalli wrote:
>>>> Some couple of ways we think could be:
>>>> [1] Check if these bits are enabled by Platform at boot time, clear them
>>>> only it is set during hotplug flow.
>>>> [2] Clear them unconditionally as I did..
>>>> [3] Enable 10-bits tags in Linux when a device is probed just like how
>>>> we do for ARI..
>>>>
>>>> Similarly call pci_enable_atomic_ops_to_root() during a hot add..
>>>
>>> Personally I'm fine with option [2].  If you or Bjorn prefer option [3],
>>> I'm fine with that as well.
>>
>> Looking forward for Bjorn comments!
> 
> You may want to consider first doing [2], i.e. clear the DevCtl2 bits
> on hot removal, and then in a separate step do [3], i.e. add support
> for enabling 10 bit tags and atomic ops in the kernel.  Having that
> would certainly be useful, but it's more complex than just clearing
> the DevCtl2 bits on unplug.  So you may want to do the latter as a
> stop-gap.

Okay I just sent v3 now. I will take care of this in v4 along with other
comments in v3.

Thanks,
Smita
> 
> Thanks,
> 
> Lukas