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

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Message-ID: <20240503102006.GI3927860@ragnatech.se>
Date: Fri, 3 May 2024 12:20:06 +0200
From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
To: Andrew Lunn <andrew@...n.ch>
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

Hi Andrew,

Thanks for your review.

On 2024-04-16 00:55:12 +0200, Andrew Lunn wrote:

<snip>

> > +static int rtsn_mii_access_indirect(struct mii_bus *bus, bool read, 
> > int phyad,
> > +				    int devnum, int regnum, u16 data)
> > +{
> > +	int ret;
> > +
> > +	ret = rtsn_mii_access(bus, false, phyad, MII_MMD_CTRL, devnum);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = rtsn_mii_access(bus, false, phyad, MII_MMD_DATA, regnum);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = rtsn_mii_access(bus, false, phyad, MII_MMD_CTRL,
> > +			      devnum | MII_MMD_CTRL_NOINCR);
> 
> This looks to be C45 over C22. phylib core knows how to do this, since
> it should be the same for all PHYs which implement C45 over C22. So
> there is no need for you to implement it again.
> 
> > +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.

The allocator in question here could possibly be alloc_mdio_bitbang(), 
but I see no easy way for me to implement the mdiobb_ops struct. Is 
there a different bus implementation I should use that is able to talk 
C45 over C22 ?

-- 
Kind Regards,
Niklas Söderlund