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Subject: Re: [PATCH v4 1/3] PCI: pciehp: Add support for disabling in-band
 presence
From:   Stuart Hayes <stuart.w.hayes@gmail.com>
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     Austin Bolen <austin_bolen@dell.com>,
        Keith Busch <keith.busch@intel.com>,
        Alexandru Gagniuc <mr.nuke.me@gmail.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        "Gustavo A . R . Silva" <gustavo@embeddedor.com>,
        Sinan Kaya <okaya@kernel.org>,
        Oza Pawandeep <poza@codeaurora.org>, linux-pci@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Lukas Wunner <lukas@wunner.de>
References: <20191025190047.38130-2-stuart.w.hayes@gmail.com>
 <20191127013613.GA233706@google.com>
 <CAL5oW00Lh4v2YpX2GcDoRS2fFJjvHRsdhNjtvyYGpWOpgL=TCg@mail.gmail.com>
Message-ID: <f14d8325-8635-329f-cdc7-fd27a52b2704@gmail.com>
Date:   Tue, 31 Dec 2019 16:06:45 -0600
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On 11/26/19 8:19 PM, Stuart Hayes wrote:
> On Tue, Nov 26, 2019 at 7:36 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>>
>> On Fri, Oct 25, 2019 at 03:00:45PM -0400, Stuart Hayes wrote:
>>> From: Alexandru Gagniuc <mr.nuke.me@gmail.com>
>>>
>>> The presence detect state (PDS) is normally a logical or of in-band and
>>> out-of-band presence. As of PCIe 4.0, there is the option to disable
>>> in-band presence so that the PDS bit always reflects the state of the
>>> out-of-band presence.
>>>
>>> The recommendation of the PCIe spec is to disable in-band presence
>>> whenever supported.
>>
>> I think I'm fine with this patch, but I would like to include the
>> specific reference for this recommendation.  If you have it handy, I
>> can just insert it.
>>
> 
> The PCI Express Base Specification Revision 5.0, Version 1.0, in the
> implementation note under Appendix I ("Async Hot-Plug Reference
> Model"), it says "If OOB PD is being used and the associated DSP
> supports In-Band PD Disable, it is recommended that the In-Band PD
> Disable bit be Set, ..."
> 
> 

Is that what you were looking for?  Please let me know if there's anything
else I can do to help.