netdev - Re: [net-next: PATCH v3 5/6] net: mvpp2: enable using phylink with ACPI

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Message-ID: <CAPv3WKfdCwq=AYhARGxfRA92XcZjXYwdOj6_JLP+wOmPV8xxzQ@mail.gmail.com>
Date:   Wed, 23 Jun 2021 23:45:04 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>,
        Grzegorz Bernacki <gjb@...ihalf.com>, upstream@...ihalf.com,
        Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@....com>,
        Jon Nettleton <jon@...id-run.com>,
        Tomasz Nowicki <tn@...ihalf.com>, rjw@...ysocki.net,
        lenb@...nel.org
Subject: Re: [net-next: PATCH v3 5/6] net: mvpp2: enable using phylink with ACPI

Hi,

śr., 23 cze 2021 o 22:37 Andrew Lunn <andrew@...n.ch> napisał(a):
>
> > +static bool mvpp2_use_acpi_compat_mode(struct fwnode_handle *port_fwnode)
> > +{
> > +     if (!is_acpi_node(port_fwnode))
> > +             return false;
> > +
> > +     return (!fwnode_property_present(port_fwnode, "phy-handle") &&
> > +             !fwnode_property_present(port_fwnode, "managed") &&
> > +             !fwnode_get_named_child_node(port_fwnode, "fixed-link"));
>
> I'm not too sure about this last one. You only use fixed-link when
> connecting to an Ethernet switch. I doubt anybody will try ACPI and a
> switch. It has been agreed, ACPI is for simple hardware, and you need
> to use DT for advanced hardware configurations.
>
> What is your use case for fixed-link?
>

Regardless of the "simple hardware" definition or whether DSA + ACPI
feasibility, you can still have e.g. the switch left in "unmanaged"
mode (or whatever the firmware configures), connected via fixed-link
to the MAC. The same effect as booting with DT, but not loading the
DSA/switch driver - the "CPU port" can be used as a normal netdev
interface.

I'd also prefer to have all 3 major interface types supported in
phylink, explicitly checked in the driver - it has not been supported
yet, but can be in the future, so let's have them covered in the
backward compatibility check.

Best regards,
Marcin