Subject: Re: [PATCH net-next v3 4/4] net: mdio: reset PHY before attempting to access registers in fwnode_mdiobus_register_phy

From: Buday Csaba <[email-masked]>
Date: Tue, 21 Oct 2025 09:24:18 +0200

Thank you!
I do not know how that slipped.
I will fix it in v4.

Regards,
Csaba

On Mon, Oct 20, 2025 at 11:16:11AM +0200, Philipp Zabel wrote:
> On Fr, 2025-10-17 at 18:10 +0200, Buday Csaba wrote:
> > Implement support for the `phy-id-read-needs-reset` device tree
> > property.
> > 
> > When the ID of an ethernet PHY is not provided by the 'compatible'
> > string in the device tree, its actual ID is read via the MDIO bus.
> > For some PHYs this could be unsafe, since a hard reset may be
> > necessary to safely access the MDIO registers.
> > 
> > This patch performs the hard-reset before attempting to read the ID,
> > when the mentioned device tree property is present.
> > 
> > Signed-off-by: Buday Csaba <[email-masked]>
> > ---
> > V2 -> V3: kernel-doc replaced with a comment (fixed warning)
> > V1 -> V2:
> >  - renamed DT property `reset-phy-before-probe` to
> >   `phy-id-read-needs-reset`
> 
> Not completely, see below.
> 
> >  - renamed fwnode_reset_phy_before_probe() to
> >    fwnode_reset_phy()
> >  - added kernel-doc for fwnode_reset_phy()
> >  - improved error handling in fwnode_reset_phy()
> > ---
> >  drivers/net/mdio/fwnode_mdio.c | 35 +++++++++++++++++++++++++++++++++-
> >  1 file changed, 34 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
> > index ba7091518..8e8f9182a 100644
> > --- a/drivers/net/mdio/fwnode_mdio.c
> > +++ b/drivers/net/mdio/fwnode_mdio.c
> > @@ -114,6 +114,36 @@ int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
> >  }
> >  EXPORT_SYMBOL(fwnode_mdiobus_phy_device_register);
> >  
> > +/* Hard-reset a PHY before registration */
> > +static int fwnode_reset_phy(struct mii_bus *bus, u32 addr,
> > +			    struct fwnode_handle *phy_node)
> > +{
> > +	struct mdio_device *tmpdev;
> > +	int err;
> > +
> > +	tmpdev = mdio_device_create(bus, addr);
> > +	if (IS_ERR(tmpdev))
> > +		return PTR_ERR(tmpdev);
> > +
> > +	fwnode_handle_get(phy_node);
> > +	device_set_node(&tmpdev->dev, phy_node);
> > +	err = mdio_device_register_reset(tmpdev);
> > +	if (err) {
> > +		mdio_device_free(tmpdev);
> > +		return err;
> > +	}
> > +
> > +	mdio_device_reset(tmpdev, 1);
> > +	mdio_device_reset(tmpdev, 0);
> > +
> > +	mdio_device_unregister_reset(tmpdev);
> > +
> > +	mdio_device_free(tmpdev);
> > +	fwnode_handle_put(phy_node);
> > +
> > +	return 0;
> > +}
> > +
> >  int fwnode_mdiobus_register_phy(struct mii_bus *bus,
> >  				struct fwnode_handle *child, u32 addr)
> >  {
> > @@ -129,8 +159,11 @@ int fwnode_mdiobus_register_phy(struct mii_bus *bus,
> >  		return PTR_ERR(mii_ts);
> >  
> >  	is_c45 = fwnode_device_is_compatible(child, "ethernet-phy-ieee802.3-c45");
> > -	if (is_c45 || fwnode_get_phy_id(child, &phy_id))
> > +	if (is_c45 || fwnode_get_phy_id(child, &phy_id)) {
> > +		if (fwnode_property_present(child, "reset-phy-before-probe"))
> 
> Commit message says this should be "phy-id-read-needs-reset" now.
> 
> regards
> Philipp
>