Re: [PATCH net-next 2/2] net: pcs: xpcs: select operating mode for 10G-baseR capable PCS

[Andrew Lunn <andrew@lunn.ch>]

> I have spotted a very obvious flaw in my reasoning above: the special
> case logic for FBNIC that suppresses the initial XPCS reset.
> Unfortunately the version history doesn't mention what bad thing we
> can avoid by suppressing the reset (perhaps a reset can clobber values
> such as PCS_TYPE_SEL that are injected by the firmware).

At a guess, they want to avoid disconnecting the BMC, which is sharing
the link. The firmware is probably doing an initial configuration of
the PCS, so that the BMC gets link, before the host boots. A reset
would upset that.

But just a guess.

We need a better story for links shared by BMCs. phylink should be
told, so it can tell the PCS to be extra special careful not to upset
the settings if they are already good. It can also reuse some of the
WoL code to not actually down the PCS, PHY, SFP etc when
phylink_stop() is called etc. But so far nobody has stepped up to do
that.

	Andrew