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Date: Tue, 4 Jun 2024 12:04:57 +0300
From: Serge Semin <fancer.lancer@gmail.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Andrew Lunn <andrew@lunn.ch>, Heiner Kallweit <hkallweit1@gmail.com>, 
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Subject: Re: [PATCH net-next v2 10/10] net: stmmac: Add DW XPCS specified via
 "pcs-handle" support
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On Mon, Jun 03, 2024 at 10:03:54AM +0100, Russell King (Oracle) wrote:
> On Mon, Jun 03, 2024 at 11:54:22AM +0300, Serge Semin wrote:
> > >  	if (priv->plat->pcs_init) {
> > >  		ret = priv->plat->pcs_init(priv);
> > 
> > > +	} else if (fwnode_property_present(devnode, "pcs-handle")) {
> > > +		pcsnode = fwnode_find_reference(devnode, "pcs-handle", 0);
> > > +		xpcs = xpcs_create_fwnode(pcsnode, mode);
> > > +		fwnode_handle_put(pcsnode);
> > > +		ret = PTR_ERR_OR_ZERO(xpcs);
> > 
> > Just figured, we might wish to be a bit more portable in the
> > "pcs-handle" property semantics implementation seeing there can be at
> > least three different PCS attached:
> > DW XPCS
> > Lynx PCS
> > Renesas RZ/N1 MII
> > 
> > Any suggestion of how to distinguish the passed handle? Perhaps
> > named-property, phandle argument, by the compatible string or the
> > node-name?
> 

> I can't think of a reasonable solution to this at the moment. One
> solution could be pushing this down into the platform code to deal
> with as an interim solution, via the new .pcs_init() method.
> 
> We could also do that with the current XPCS code, since we know that
> only Intel mGBE uses xpcs. This would probably allow us to get rid
> of the has_xpcs flag.

Basically you suggest to move the entire stmmac_pcs_setup() to the
platforms, don't you? The patch 9 of this series indeed could have
been converted to just moving the entire PCS-detection loop from
stmmac_pcs_setup() to the Intel-specific pcs_init.

But IMO some default/generic code would be still useful to preserve in
the stmmac_pcs_setup() method. When it comes to the fwnode-based
platform we at least could be falling back to the default DW XPCS
device registration if no plat_stmmacenet_data::pcs_init() callback
was specified and there was the "pcs-handle" property found,
especially seeing DW *MAC and DW XPCS are of the same vendor.

Based on that I can convert patch 9 of this series to introducing the
pcs_init() callback in the Intel mGBE driver, but preserve the
semantics of the rest of the series changes.

-Serge(y)

> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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