linux-kernel - Re: [PATCH v2 4/4] net: mdio: reset PHY before attempting to access registers in fwnode_mdiobus_register

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Message-ID: <aPHxZrLrCyjVO9cR@debianbuilder>
Date: Fri, 17 Oct 2025 09:33:58 +0200
From: Buday Csaba <buday.csaba@...lan.hu>
To: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Florian Fainelli <f.fainelli@...il.com>,
	<netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] net: mdio: reset PHY before attempting to access
 registers in fwnode_mdiobus_register_phy

Dear Maintainers,

I am about the submit the v3 version of these patches, hopefully the last
iteration. I think I managed to elimante all failures and almost all of
the warnings, except one: patchwork complies, that not all the maintainers
are CC'ed.

I have used get_maintainers.pl to get the address list. I am on the
net-next tree. Is there a problem with get_maintainers.pl or with
patchwork? Can I ignore that warning?

Reference:
https://patchwork.kernel.org/project/netdevbpf/patch/20251015134503.107925-1-buday.csaba@prolan.hu/

Thank you,
Csaba

On Wed, Oct 15, 2025 at 03:45:03PM +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.
> 
> There were previous attempts to implement such functionality, I
> tried to collect a few of these (see links).
> 
> Link: https://lore.kernel.org/lkml/1499346330-12166-2-git-send-email-richard.leitner@skidata.com/
> Link: https://lore.kernel.org/all/20230405-net-next-topic-net-phy-reset-v1-0-7e5329f08002@pengutronix.de/
> Link: https://lore.kernel.org/netdev/20250709133222.48802-4-buday.csaba@prolan.hu/
> 
> Signed-off-by: Buday Csaba <buday.csaba@...lan.hu>
> ---
> V1 -> V2:
>  - renamed DT property `reset-phy-before-probe` to
>   `phy-id-read-needs-reset`
>  - 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 | 37 +++++++++++++++++++++++++++++++++-
>  1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
> index ba7091518..6987b1a51 100644
> --- a/drivers/net/mdio/fwnode_mdio.c
> +++ b/drivers/net/mdio/fwnode_mdio.c
> @@ -114,6 +114,38 @@ int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
>  }
>  EXPORT_SYMBOL(fwnode_mdiobus_phy_device_register);
>  
> +/**
> + * fwnode_reset_phy() - 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 +161,11 @@ 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"))
> +			fwnode_reset_phy(bus, addr, child);
>  		phy = get_phy_device(bus, addr, is_c45);
> +	}
>  	else
>  		phy = phy_device_create(bus, addr, phy_id, 0, NULL);
>  	if (IS_ERR(phy)) {
> -- 
> 2.39.5
>