Re: [PATCH] lspci: Don't report PCIe link downgrades for downstream ports

[Matthew Wilcox <willy@infradead.org>]

On Sun, Mar 21, 2021 at 05:09:05PM +0100, Pali Rohár wrote:
> Different thing is when you have Gen2 PCIe Bridge which can operate at
> 5 GT/s but you connect only Gen1 PCIe card under it (which operates only
> at 2.5 GT/s).
> 
> In this case Root or Downstream port of PCIe Bridge is running at lower
> "downgraded" speed but card (on the upstream end of the link) is running
> at maximal speed (not downgraded).
> 
> So in this case proposed patch does not report "downgraded" state
> neither on Root/Downstream Bridge part nor on card part.
> 
> Is it correct? Should not lspci report in this case _somewhere_ that
> link is downgraded and is not running at the full speed?

I suppose it depends why you think it's important that "downgraded"
is reported.  If you want it to mean "you've plugged a slow card into a
port that's capable of more", then you're right.  If you want it to mean
"autonegotiation went wrong", then you actually don't want downgraded
to be reported in the scenarios you outlined.

Dmitry?  What did you /want/ it to mean?