netdev - Re: [PATCH RESEND net] net: phy: xgmiitorgmii: Support generic PHY status read

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Message-ID: <CAFcVECKU7zD2ms76GH-mF2GxCtNr4RQ+2=jN_xppueQsUSq2wg@mail.gmail.com>
Date:   Sat, 9 Mar 2019 17:39:12 +0530
From:   Harini Katakam <harinik@...inx.com>
To:     Michal Simek <michal.simek@...inx.com>
Cc:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH RESEND net] net: phy: xgmiitorgmii: Support generic PHY
 status read

Hi Andrew,
On Thu, Feb 28, 2019 at 1:03 PM Harini Katakam <harinik@...inx.com> wrote:
>
> Hi,
> On Wed, Feb 27, 2019 at 2:35 PM Harini Katakam <harinik@...inx.com> wrote:
> >
> > Hi Andrew, Paul,
> >
> > On Wed, Feb 27, 2019 at 2:15 PM Michal Simek <michal.simek@...inx.com> wrote:
> > >
> > > On 21. 02. 19 12:03, Michal Simek wrote:
> > > > On 21. 02. 19 11:24, Paul Kocialkowski wrote:
> > > >> Hi,
> > > >>
> > > >> On Wed, 2019-02-20 at 07:58 +0100, Michal Simek wrote:
> > > >>> Hi,
> > > >>>
> > > >>> On 19. 02. 19 18:25, Andrew Lunn wrote:
> <snip>
> > > >> Understood. I think we need to start a discussion about how the general
> > > >> design of this driver can be improved.
> > > >>
> > > >> In particular, I wonder if it could work better to make this driver a
> > > >> PHY driver that just redirects all its ops to the actual PHY driver,
> > > >> except for read_status where it should also add some code.
> >
> > Thanks, I'm looking into this option and also a way to expose the correct
> > interface mode setting as you mentioned below. I'll get back before the
> > end of the week. Please do let me know if you have any further suggestions.
> >
> This IP does not have a PHY identifier or status register that can be accessed
> from the phy framework. We could discuss with our design team to add these
> in the future. But that would take sometime and this version should be still be
> supported. Also, if this IP has a PHY driver, then two phy drivers would have
> to be probed which are connected in a serial manner and I believe I'll have to
> update the framework to support that. Could you please let me know if you have
> any inputs on this?
> OR since this is just a bridge IP, is it acceptable to address the error cases?
> -> Module loading/unloading
> -> Spinlocks for protection
> -> Correct phy mode information to the driver.
> -> Any other concerns
> I could do a respin of this patch after addressing Andrew's comments:
> https://patchwork.kernel.org/patch/9290231/

Related to this, I have a query on how the DT node for gmii2rgmii should look.
One of the users of gmii2rgmii is Cadence macb driver. In Xilinx tree, we use
this piece of code to register this mdiobus:
+ mdio_np = of_get_child_by_name(np, "mdio");
+ if (mdio_np) {
+ of_node_put(mdio_np);
+ err = of_mdiobus_register(bp->mii_bus, mdio_np);
+ if (err)
+ goto err_out_unregister_bus;

And the DT node looks like this:
ethernet {
    phy-mode = "gmii";
    phy-handle = <&extphy>;

    mdio {
        extphy {
            reg = <x>;
        };
        gmii_to_rgmii{
            compatible = "xlnx,gmii-to-rgmii-1.0";
            phy-handle = <&extphy>;
            reg = <x>;
        };
    };
};

Could you please clarify if phy-handle in ethernet should point to
external PHY or gmii2rgmii?

Regards,
Harini