Re: [PATCH net-next 3/6] net: dsa: add support for retrieving the interface mode

Russell King (Oracle)
2022-07-22T13:52:09Z

On Fri, Jul 22, 2022 at 02:59:36PM +0200, Marek Behún wrote:
> The 2.5GBASE-X PCS does not support Clause 37 Auto-Negotiation.
> Hence, the 1000BASE-X PCS is expected to have its Clause 37
> Auto-Negotiation functionality disabled so that the /C/ ordered set
> will not be transmitted. If a 2.5GBASE-X PCS receives /C/ ordered
> set, then undefined behavior may occur.
> ...

The reason that's probably stated is because there hasn't been any
standardisation of it, different implementations behave differently,
so they can't define a standard behaviour without breaking what's
already out there.

With mvneta, the reality is that the 2.5G speed is implemented by
changing the clock configuration in the COMPHY block (serdes) - which
basically clocks everything 2.5x faster. I seem to remember mvpp2 is
the same deal.

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