netdev - Re: [net-next PATCH v2 06/14] net: mdiobus: Introduce fwnode_mdiobus_register

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Date:   Fri, 18 Dec 2020 11:04:23 +0530
From:   Calvin Johnson <calvin.johnson@....nxp.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Grant Likely <grant.likely@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Cristi Sovaiala <cristian.sovaiala@....com>,
        Florin Laurentiu Chiculita <florinlaurentiu.chiculita@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Pieter Jansen Van Vuuren <pieter.jansenvv@...boosystems.io>,
        Jon <jon@...id-run.com>, "linux.cj" <linux.cj@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Diana Madalina Craciun <diana.craciun@....com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        netdev <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [net-next PATCH v2 06/14] net: mdiobus: Introduce
 fwnode_mdiobus_register_phy()

On Tue, Dec 15, 2020 at 07:33:40PM +0200, Andy Shevchenko wrote:
> On Tue, Dec 15, 2020 at 6:44 PM Calvin Johnson
> <calvin.johnson@....nxp.com> wrote:
> >
> > Introduce fwnode_mdiobus_register_phy() to register PHYs on the
> > mdiobus. From the compatible string, identify whether the PHY is
> > c45 and based on this create a PHY device instance which is
> > registered on the mdiobus.
> 
> ...
> 
> > +int fwnode_mdiobus_register_phy(struct mii_bus *bus,
> > +                               struct fwnode_handle *child, u32 addr)
> > +{
> > +       struct mii_timestamper *mii_ts;
> > +       struct phy_device *phy;
> > +       const char *cp;
> > +       bool is_c45;
> > +       u32 phy_id;
> > +       int rc;
> 
> > +       if (is_of_node(child)) {
> > +               mii_ts = of_find_mii_timestamper(to_of_node(child));
> > +               if (IS_ERR(mii_ts))
> > +                       return PTR_ERR(mii_ts);
> > +       }
> 
> Perhaps
> 
>                mii_ts = of_find_mii_timestamper(to_of_node(child));
> 
> > +
> > +       rc = fwnode_property_read_string(child, "compatible", &cp);
> > +       is_c45 = !(rc || strcmp(cp, "ethernet-phy-ieee802.3-c45"));
> > +
> > +       if (is_c45 || fwnode_get_phy_id(child, &phy_id))
> > +               phy = get_phy_device(bus, addr, is_c45);
> > +       else
> > +               phy = phy_device_create(bus, addr, phy_id, 0, NULL);
> > +       if (IS_ERR(phy)) {
> 
> > +               if (mii_ts && is_of_node(child))
> > +                       unregister_mii_timestamper(mii_ts);
> 
> if (!IS_ERR_OR_NULL(mii_ts))
>  ...
> 
> However it points to the question why unregister() doesn't handle the
> above cases.
> I would expect unconditional call to unregister() here.

This is following the logic defined in of_mdiobus_register_phy().
https://elixir.bootlin.com/linux/latest/source/drivers/net/mdio/of_mdio.c#L107

	mii_ts = of_find_mii_timestamper(child);
	if (IS_ERR(mii_ts))
		return PTR_ERR(mii_ts);

I think the logic above is correct because this function returns only if
of_find_mii_timestamper() returns error. On NULL return, it proceeds further.

> 
> > +               return PTR_ERR(phy);
> > +       }
> > +
> > +       if (is_acpi_node(child)) {
> > +               phy->irq = bus->irq[addr];
> > +
> > +               /* Associate the fwnode with the device structure so it
> > +                * can be looked up later.
> > +                */
> > +               phy->mdio.dev.fwnode = child;
> > +
> > +               /* All data is now stored in the phy struct, so register it */
> > +               rc = phy_device_register(phy);
> > +               if (rc) {
> > +                       phy_device_free(phy);
> > +                       fwnode_handle_put(phy->mdio.dev.fwnode);
> > +                       return rc;
> > +               }
> > +
> > +               dev_dbg(&bus->dev, "registered phy at address %i\n", addr);
> > +       } else if (is_of_node(child)) {
> > +               rc = of_mdiobus_phy_device_register(bus, phy, to_of_node(child), addr);
> > +               if (rc) {
> 
> > +                       if (mii_ts)
> > +                               unregister_mii_timestamper(mii_ts);
> 
> Ditto.
> 
> > +                       phy_device_free(phy);
> > +                       return rc;
> > +               }
> > +
> > +               /* phy->mii_ts may already be defined by the PHY driver. A
> > +                * mii_timestamper probed via the device tree will still have
> > +                * precedence.
> > +                */
> 
> > +               if (mii_ts)
> > +                       phy->mii_ts = mii_ts;
> 
> How is that defined? Do you need to do something with an old pointer?

As the comment says, I think PHY drivers which got invoked before calling
of_mdiobus_register_phy() may have defined phy->mii_ts.

> 
> > +       }
> > +       return 0;
> > +}
> 
> -- 
> With Best Regards,
> Andy Shevchenko