Re: [PATCH v2 net-next 03/15] net: mdio: add generic driver for NXP SJA1110 100BASE-TX embedded PHYs

[Vladimir Oltean <vladimir.oltean@nxp.com>]

On Thu, Jan 22, 2026 at 02:20:22PM +0200, Andy Shevchenko wrote:
> On Thu, Jan 22, 2026 at 12:56:42PM +0200, Vladimir Oltean wrote:
> > This is the standalone variant of drivers/net/dsa/sja1105/sja1105_mdio.c.
> > Same kind of differences between this driver and the embedded DSA one
> > apply: regmap is being used for register access, and addresses are
> > multiplied by 4 with regmap.
> > 
> > In fact this is so generic that there is nothing NXP SJA1110 specific
> > about it at all, and just instantiates mdio-regmap. I decided to name it
> > mdio-regmap-simple.c in the style of drivers/mfd/simple-mfd-i2c.c which
> > has support for various vendor compatible strings.
> 
> ...
> 
> > +#include <linux/module.h>
> > +#include <linux/of_mdio.h>
> > +#include <linux/phy.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/regmap.h>
> > +#include <linux/mdio/mdio-regmap.h>
> 
> ...
> 
> > +static const struct mdio_regmap_simple_data nxp_sja1110_base_tx = {
> > +	.valid_addr = 0,
> > +	.autoscan = false,
> > +};
> 
> Actually the  { } is enough to initialise that. But if you want to be super
> explicit... :-)
> ...

Yes, I guess I do.

> > +static int mdio_regmap_simple_probe(struct platform_device *pdev)
> > +{
> > +	const struct mdio_regmap_simple_data *data;
> > +	struct mdio_regmap_config config = {};
> > +	struct device *dev = &pdev->dev;
> > +	struct regmap *regmap;
> > +	struct mii_bus *bus;
> > +
> > +	if (!dev->of_node || !dev->parent)
> 
> dev->of_node check is not needed, see below.

Oh.... this is a bug. dev->of_node should have been propagated to
devm_mdio_regmap_register() -> devm_mdiobus_register(), turning it into
devm_of_mdiobus_register().

It shows that my SJA1110 testing platform (Bluebox 3) doesn't have the
CBTX PHY routed to pinout, since I didn't catch this... I'll fix this
for v3.

> > +		return -ENODEV;
> > +
> > +	regmap = dev_get_regmap(dev->parent, NULL);
> > +	if (!regmap)
> > +		return -ENODEV;
> > +
> > +	data = device_get_match_data(dev);
> > +
> > +	config.regmap = regmap;
> > +	config.parent = dev;
> > +	config.name = dev_name(dev);
> > +	/* The resource is optional, provided for finding the registers
> > +	 * within a device-wide non-MMIO regmap
> > +	 */
> > +	config.resource = platform_get_resource(pdev, IORESOURCE_REG, 0);
> 
> > +	if (data) {
> 
> We may always require data to be present. As you use a default one anyway.
> 
> > +		config.valid_addr = data->valid_addr;
> > +		config.autoscan = data->autoscan;
> > +	}
> 
> And if it is not provided we will have a crash which is fine. It will just
> point that the code was not ever been run on real HW.

Hmm. This patch is super old, so I'm revisiting it with foreign eyes,
same as you.

I think the case with .valid_addr = 0 and .autoscan = false will
constitute the vast majority of instantiations of this driver.
I would like to avoid the proliferation of the same basic config with
100 different names (nxp_sja1110_base_tx, etc).

So for v3 I'm planning to:
- rename nxp_sja1110_base_tx to mdio_regmap_simple_default_data
- delete the "if (data)" conditional and directly assign from
  device_get_match_data() to the config structure

Thanks for taking a look.

> > +	return PTR_ERR_OR_ZERO(devm_mdio_regmap_register(dev, &config));
> > +}
> 
> ...
> 
> > +static struct platform_driver mdio_regmap_simple_driver = {
> > +	.probe = mdio_regmap_simple_probe,
> > +	.driver = {
> > +		.name = "mdio-regmap-simple",
> > +		.of_match_table = mdio_regmap_simple_match,
> > +	},
> > +};
> 
> > +
> 
> Unneeded blank line.

Ok.

> > +module_platform_driver(mdio_regmap_simple_driver);
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>