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Date:   Thu, 9 Jul 2020 14:24:55 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Manish Raturi <raturi.manish@gmail.com>
Cc:     linux-pci@vger.kernel.org
Subject: Re: Dump of registers during endpoint link down
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On Thu, Jul 09, 2020 at 12:44:24PM +0530, Manish Raturi wrote:
> Hi Team,
> 
> I have a generic query , if an hotplug pcie endpoint connected to the
> CPU root port shows link down, then from the debugging perspective
> w.r.t PCIE what all register can be dump during the failure condition,
> what I can think of is these registers from the root port side
> 
> 1) Link status /control/capability
> 2) Slot status /control/capability
> 3) Lane error status registers.
> 
> Anything else we can dump which gives us more insight into the issue.
> Also is there anything by which we can check from PCIE clock
> perspective.

If you have this:

  Root Port ----- Endpoint

and the Link is down, you won't be able to read any registers from the
Endpoint.  You can dump all the Root Port registers, of course, e.g.,
with "lspci -vvvxxxx".