From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: abhijit <abhijitnaik27@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: Doubt on first access for PCIe device
Date: Wed, 19 Apr 2017 11:26:52 +0100 [thread overview]
Message-ID: <20170419102652.GA23487@red-moon> (raw)
In-Reply-To: <50712b3b-2943-0b78-9413-257f33b26c3f@gmail.com>
On Tue, Apr 11, 2017 at 07:45:40PM +0530, abhijit wrote:
>
> Hi All,
>
> I was referring Linux code for PCIe enumeration and I have one doubt
> w.r.t to very first operation that must be done on device.
>
> Currently while scanning for device, we directly read vendor ID from
> device. But PCIE base specification
> "CB-PCI_Express_Base_4.0r0.7_November-11-2016.pdf" section 2.2.6.2
> specifies that,
>
> "Functions must capture the Bus and Device Numbers supplied with all
> Type 0 Configuration Write Requests completed by the Function and
> supply these numbers in the Bus and Device Number fields of the
> Requester ID for all Requests initiated by the Device/Function."
Please note:
"for all Requests initiated by the Device/Function".
^^^^^^^^^
> Here I am assuming, the completer ID will be device number and
> function number that will eventually programmed in to device. In
> that case, my question is, without first write, how read
> request(VENDOR ID read) is serviced/routed?
That's not initiated by the endpoint device, it is routed by
requester ID, which is the requester ID of the configuration
request - ie master (ie root complex) requester ID.
Read 2.2.9 - Completion rules
HTH,
Lorenzo
next prev parent reply other threads:[~2017-04-19 10:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-11 14:15 Doubt on first access for PCIe device abhijit
2017-04-19 5:00 ` Jon Masters
2017-04-19 10:26 ` Lorenzo Pieralisi [this message]
[not found] ` <CANaY3hNcB0Yk=2f7S+J2r+wtd6T7mLd+ZNprNHFkMegZzvx7pQ@mail.gmail.com>
2017-04-21 15:59 ` Lorenzo Pieralisi
2017-04-24 6:22 ` abhijit
2017-04-24 10:01 ` Lorenzo Pieralisi
2017-04-24 11:15 ` abhijit
2017-04-21 10:07 ` abhijit
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