linux-kernel - Re: [PATCH net-next] net: dsa: mt7530: register OF node for internal MDIO bus

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Date: Thu, 21 Dec 2023 14:26:24 +0530
From: Ravi Gunasekaran <r-gunasekaran@...com>
To: Arınç ÜNAL <arinc.unal@...nc9.com>,
        Daniel Golle
	<daniel@...rotopia.org>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG
 Qingfang <dqfext@...il.com>, Sean Wang <sean.wang@...iatek.com>,
        Andrew Lunn
	<andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean
	<olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni
	<pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
CC: David Bauer <mail@...id-bauer.net>, <mithat.guner@...ont.com>,
        <erkin.bozoglu@...ont.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        Ravi Gunasekaran <r-gunasekaran@...com>
Subject: Re: [PATCH net-next] net: dsa: mt7530: register OF node for internal
 MDIO bus



On 12/20/23 11:05 PM, Arınç ÜNAL wrote:
> From: David Bauer <mail@...id-bauer.net>
> 
> The MT753x switches provide a switch-internal MDIO bus for the embedded
> PHYs.
> 
> Register a OF sub-node on the switch OF-node for this internal MDIO bus.
> This allows to configure the embedded PHYs using device-tree.
> 
> Signed-off-by: David Bauer <mail@...id-bauer.net>
> Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
> ---
>  drivers/net/dsa/mt7530.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> index 391c4dbdff42..f8ecc354630b 100644
> --- a/drivers/net/dsa/mt7530.c
> +++ b/drivers/net/dsa/mt7530.c
> @@ -2155,10 +2155,13 @@ mt7530_setup_mdio(struct mt7530_priv *priv)
>  {
>  	struct dsa_switch *ds = priv->ds;
>  	struct device *dev = priv->dev;
> +	struct device_node *np, *mnp;
>  	struct mii_bus *bus;
>  	static int idx;
>  	int ret;
>  
> +	np = priv->dev->of_node;
> +
>  	bus = devm_mdiobus_alloc(dev);
>  	if (!bus)
>  		return -ENOMEM;
> @@ -2177,7 +2180,9 @@ mt7530_setup_mdio(struct mt7530_priv *priv)
>  	if (priv->irq)
>  		mt7530_setup_mdio_irq(priv);
>  
> -	ret = devm_mdiobus_register(dev, bus);
> +	mnp = of_get_child_by_name(np, "mdio");

If the node is not found, then the return value would be NULL.
Though devm_of_mdiobus_register() and of_node_put() take care of NULL references,
other drivers that use devm_of_mdiobus_register() mostly perform a early exit if the node is NULL.


> +	ret = devm_of_mdiobus_register(dev, bus, mnp);
> +	of_node_put(mnp);
>  	if (ret) {
>  		dev_err(dev, "failed to register MDIO bus: %d\n", ret);
>  		if (priv->irq)

-- 
Regards,
Ravi