netdev - Re: [net-next] net: ethernet: rtsn: Add support for Renesas Ethernet-TSN

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Message-ID: <e3ce12b0-fb5d-49d7-a529-9ea7392b80ca@lunn.ch>
Date: Fri, 3 May 2024 13:59:52 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [net-next] net: ethernet: rtsn: Add support for Renesas
 Ethernet-TSN

> > > +static int rtsn_mii_register(struct rtsn_private *priv)
> > > +{
> > > +	struct platform_device *pdev = priv->pdev;
> > > +	struct device *dev = &pdev->dev;
> > > +	struct device_node *mdio_node;
> > > +	struct mii_bus *mii;
> > > +	int ret;
> > > +
> > > +	mii = mdiobus_alloc();
> > > +	if (!mii)
> > > +		return -ENOMEM;
> > > +
> > > +	mdio_node = of_get_child_by_name(dev->of_node, "mdio");
> > > +	if (!mdio_node) {
> > > +		ret = -ENODEV;
> > > +		goto out_free_bus;
> > > +	};
> > > +
> > > +	mii->name = "rtsn_mii";
> > > +	sprintf(mii->id, "%s-%x", pdev->name, pdev->id);
> > > +	mii->priv = priv;
> > > +	mii->read = rtsn_mii_read;
> > > +	mii->write = rtsn_mii_write;
> > > +	mii->read_c45 = rtsn_mii_read_c45;
> > > +	mii->write_c45 = rtsn_mii_write_c45;
> > 
> > Just leave these two empty, and the core will do C45 over C22 for you.
> 
> Does this not require the bus to be created/allocated with an 
> implementation that support this, for example mdio_i2c_alloc() or 
> alloc_mdio_bitbang()?  This bus is allocated with mdiobus_alloc() which 
> do not implement this. Removing the C45 functions here result in 
> __mdiobus_c45_read() returning -EOPNOTSUPP as bus->read_c45 is not set.

phy_read_mmd():
  __phy_read_mmd():
      mmd_phy_read():

So is is_c45 is true?

I would expect it to be false, so that it then uses

	mmd_phy_indirect(bus, phy_addr, devad, regnum);
	/* Write the data into MMD's selected register */
	return __mdiobus_write(bus, phy_addr, MII_MMD_DATA, val);

which is C45 over C22.

If is_c45 is true, what is setting it true?

      Andrew