[PATCH net-next v12 08/18] net: ethernet: mtk_eth_soc: fix 1000Base-X and 2500Base-X modes

[Vladimir Oltean]

On Wed, Mar 08, 2023 at 01:12:10PM +0000, Russell King (Oracle) wrote:
> So, what I would want to do is to move the decision about whether
> the PCS should enable in-band into the phylink core code instead
> of these random decisions being made in each PCS.
> 
> At that point, we can then make the decision about whether the
> ethtool autoneg bit should affect whether the PCS uses inband
> depending on whether the PCS is effectively the media facing
> entity, or whether there is a PHY attached - and if there is a PHY
> attached, ask the PHY whether it will be using in-band or not.
> 
> This also would give a way to ensure that all PCS adopt the same
> behaviour.
> 
> Does that sound a reasonable approach?
> 
> Strangely, I already have some patches along those lines in my
> net-queue branch. See:
> 
> net: phylink: add helpers for decoding mode
> net: use phylink_mode_*() helpers
> net: phylink: split PCS in-band from inband mode
> 
> It's nowhere near finished though, it was just an idea back in
> 2021 when the problem of getting rid of differing PCS behaviours
> was on my mind.

Having looked at those patches
(http://git.armlinux.org.uk/cgit/linux-arm.git/commit/?h=net-queue&id=a632167d226cf95d92cd887b2f1678e1539833b1)
and seen the way in which they are incomplete, could you sketch here how
do you see an actual pcs_validate() implementation making use of the new
"mode" argument?

I'd expect there to be some logic which changes the "mode", if the PCS
validation with the existing one fails... or?