[RFC PATCH 01/10] net: stmmac: move XPCS lifetime management to platform drivers

[Coia Prant]

Maxime Chevallier <maxime.chevallier at bootlin.com> 于2026年7月15日周三 15:31写道：
>
> Hi,
>
> +Christian
>
> On 7/14/26 21:08, Coia Prant wrote:
> > The current XPCS creation logic in stmmac_pcs_setup() is problematic
> > for several reasons.
> >
> > First, if a device tree specifies a "pcs-handle" but no select_pcs()
> > callback is provided by the platform driver, the created XPCS is never
> > used. The phylink framework requires select_pcs() to actually return
> > the PCS to the core, so the pcs-handle property becomes effectively
> > useless without the matching callback. This is confusing for developers
> > who expect that specifying a pcs-handle in their device tree should be
> > sufficient to enable the PCS.
>
> I think Christian's work on fwnode PCS would help a lot with that PCS
> handling in stmmac:
>
> https://lore.kernel.org/netdev/20260618125752.1223-1-ansuelsmth@gmail.com/
>
> I don't know when Christian plans to iterate, it could be worth using
> that new fwnode mechanism here ?
>
> Maxime

Hi Maxime,

Thanks for pointing me to Christian's work. This looks like a
much-needed improvement.

I actually spent all night debugging call traces caused by the current
stmmac PCS lifetime management, and it was not a pleasant experience.
The code feels like accumulated technical debt that should be cleaned
up.

Regarding timeline: since Christian's series is still in RFC with an
uncertain merge date, I'd prefer to keep this series as-is for now, as
it solves the problem for Rockchip and has already started receiving
review feedback. Once Christian's fwnode PCS work lands in net-next,
I'm happy to rebase and convert the Rockchip glue driver to the new
interface.

One thing I'd really like to see: the ability to specify the logical
MII port instance via something like:

    pcs-handle = <&pcs MII_PortX>;

That would make the DT binding much cleaner and more flexible for
multi-port configurations.

Thanks,
Coia