netdev - Re: [PATCH net-next] net: dsa: honor "max-speed" for implicit PHYs on user ports

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Message-ID: <ba41f79205ff4c0c90de71a6be2dd4e2e9ade0f7.camel@siemens.com>
Date: Fri, 20 Dec 2024 07:30:54 +0000
From: "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>
To: "olteanv@...il.com" <olteanv@...il.com>, "andrew@...n.ch" <andrew@...n.ch>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: dsa: honor "max-speed" for implicit PHYs on
 user ports

Hi Vladimir!

On Fri, 2024-12-20 at 08:17 +0100, Alexander Sverdlin wrote:
> > On Thu, Dec 19, 2024 at 06:50:18PM +0000, Sverdlin, Alexander wrote:
> > > There are still switch drivers in tree, which only implement .phy_read/.phy_write
> > > callbacks (which means, they rely on .user_mii_bus ?), even gigabit-capable,
> > > such as vsc73xx, rtl8365mb, rtl8366rb... But I'm actually interested in an
> > > out of tree driver for a new generation of lantiq_gsw hardware, under
> > > Maxlinear branch, which is planned to be submitted upstream at some point.
> > > 
> > > The relevant question is then, is it acceptable API (.phy_read/.phy_write),
> > > or any new gigabit-capable driver must use some form of mdiobus_register
> > > to populate the MDIO bus explicitly itself?
> > 
> > See the documentation patches which I never managed to finish for general
> > future directions:
> > https://patchwork.kernel.org/project/netdevbpf/patch/20231208193518.2018114-4-vladimir.oltean@nxp.com/
> > 
> > Not explicitly having a phy-handle should be seen a legacy feature,
> > which we are forced to keep for compatibility with existing drivers.
> 
> Thanks for the references!
> 
> I've complitely missed the story of
> fe7324b93222 ("net: dsa: OF-ware slave_mii_bus")
> vs ae94dc25fd73
> ("net: dsa: remove OF-based MDIO bus registration from DSA core").
> 
> But I'm still having hard time to get the motivation behind removing
> 2 function calls from the DSA core and forcing all individual DSA drivers
> to have this very same boilerplate...
> 
> But well, if all the DSA maintainers are so committed to it, this answers
> my original question... Please ignore the patch!

However, after reading the whole referenced thread, I still have a question:
will MFD approach (with both drivers and dt-bindings) will be a requirement
for any new drivers or a simpler approach with "mdio {}" node under the
switch node will still be acceptable?

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com