netdev - RE: [PATCH net-next 6/7] net: txgbe: support copper NIC with external PHY

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Date: Tue, 25 Jul 2023 18:04:49 +0800
From: Jiawen Wu <jiawenwu@...stnetic.com>
To: "'Russell King \(Oracle\)'" <linux@...linux.org.uk>
Cc: <netdev@...r.kernel.org>,
	<andrew@...n.ch>,
	<hkallweit1@...il.com>,
	<Jose.Abreu@...opsys.com>,
	<mengyuanlou@...-swift.com>
Subject: RE: [PATCH net-next 6/7] net: txgbe: support copper NIC with external PHY

On Tuesday, July 25, 2023 4:03 PM, Russell King (Oracle) wrote:
> On Tue, Jul 25, 2023 at 10:41:46AM +0800, Jiawen Wu wrote:
> > On Monday, July 24, 2023 6:43 PM, Russell King (Oracle) wrote:
> > > On Mon, Jul 24, 2023 at 06:23:40PM +0800, Jiawen Wu wrote:
> > > > @@ -22,6 +25,9 @@ static int txgbe_get_link_ksettings(struct net_device *netdev,
> > > >  {
> > > >  	struct txgbe *txgbe = netdev_to_txgbe(netdev);
> > > >
> > > > +	if (txgbe->wx->media_type == sp_media_copper)
> > > > +		return phy_ethtool_get_link_ksettings(netdev, cmd);
> > >
> > > Why? If a PHY is attached via phylink, then phylink will automatically
> > > forward the call below to phylib.
> >
> > No, there is no phylink implemented for sp_media_copper.
> >
> > > > +
> > > >  	return phylink_ethtool_ksettings_get(txgbe->phylink, cmd);
> > >
> > > If you implement it correctly, you also don't need two entirely
> > > separate paths to configure the MAC/PCS for the results of the PHY's
> > > negotiation, because phylink gives you a _generic_ set of interfaces
> > > between whatever is downstream from the MAC and the MAC.
> >
> > For sp_media_copper, only mii bus is registered for attaching PHY.
> > Most MAC/PCS configuration is done in firmware, so it is not necessary
> > to implement phylink as sp_media_fiber.
> 
> If you do implement phylink for copper, then you don't need all these
> conditionals and the additional adjust_link implementation. In other
> words, you can re-use a lot of the code you've already added.
> 
> You don't have to provide a PCS to phylink provided you don't tell
> phylink that it's "in-band".

Do I need to create a separate software node? That would seem to
break more code of fiber initialization flow. I could try, but I'd like to
keep the two flows separate.