netdev - Re: [PATCH net 1/5] net: ethernet: mtk_eth_soc: revise mdc divider configuration

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Message-ID: <6c36505c-7af3-49f5-9141-8a655f90a2f9@lunn.ch>
Date: Mon, 14 Apr 2025 20:30:04 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Daniel Golle <daniel@...rotopia.org>
Cc: Bo-Cun Chen <bc-bocun.chen@...iatek.com>, Felix Fietkau <nbd@....name>,
	Sean Wang <sean.wang@...iatek.com>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"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>,
	Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net 1/5] net: ethernet: mtk_eth_soc: revise mdc divider
 configuration

On Mon, Apr 14, 2025 at 07:11:20PM +0100, Daniel Golle wrote:
> From: Bo-Cun Chen <bc-bocun.chen@...iatek.com>
> 
> In the current method, the MDC divider was reset to the default setting
> of 2.5MHz after the NETSYS SER. Therefore, we need to move the MDC
> divider configuration function to mtk_hw_init().
> 
> Fixes: c0a440031d431 ("net: ethernet: mtk_eth_soc: set MDIO bus clock frequency")
> Signed-off-by: Bo-Cun Chen <bc-bocun.chen@...iatek.com>
> Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 60 ++++++++++++++-------
>  1 file changed, 42 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index 43197b28b3e74..fd643cc1b7dd2 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -871,11 +871,11 @@ static const struct phylink_mac_ops mtk_phylink_ops = {
>  	.mac_enable_tx_lpi = mtk_mac_enable_tx_lpi,
>  };
>  
> -static int mtk_mdio_init(struct mtk_eth *eth)
> +static int mtk_mdio_config(struct mtk_eth *eth)
>  {
>  	unsigned int max_clk = 2500000, divider;
>  	struct device_node *mii_np;
> -	int ret;
> +	int ret = 0;
>  	u32 val;
>  
>  	mii_np = of_get_available_child_by_name(eth->dev->of_node, "mdio-bus");
> @@ -884,22 +884,6 @@ static int mtk_mdio_init(struct mtk_eth *eth)
>  		return -ENODEV;
>  	}
>  
> -	eth->mii_bus = devm_mdiobus_alloc(eth->dev);
> -	if (!eth->mii_bus) {
> -		ret = -ENOMEM;
> -		goto err_put_node;
> -	}
> -
> -	eth->mii_bus->name = "mdio";
> -	eth->mii_bus->read = mtk_mdio_read_c22;
> -	eth->mii_bus->write = mtk_mdio_write_c22;
> -	eth->mii_bus->read_c45 = mtk_mdio_read_c45;
> -	eth->mii_bus->write_c45 = mtk_mdio_write_c45;
> -	eth->mii_bus->priv = eth;
> -	eth->mii_bus->parent = eth->dev;
> -
> -	snprintf(eth->mii_bus->id, MII_BUS_ID_SIZE, "%pOFn", mii_np);
> -
>  	if (!of_property_read_u32(mii_np, "clock-frequency", &val)) {
>  		if (val > MDC_MAX_FREQ || val < MDC_MAX_FREQ / MDC_MAX_DIVIDER) {
>  			dev_err(eth->dev, "MDIO clock frequency out of range");
> @@ -922,6 +906,42 @@ static int mtk_mdio_init(struct mtk_eth *eth)
>  
>  	dev_dbg(eth->dev, "MDC is running on %d Hz\n", MDC_MAX_FREQ / divider);
>  
> +err_put_node:
> +	of_node_put(mii_np);
> +	return ret;
> +}
> +
> +static int mtk_mdio_init(struct mtk_eth *eth)
> +{
> +	struct device_node *mii_np;
> +	int ret;
> +
> +	mii_np = of_get_child_by_name(eth->dev->of_node, "mdio-bus");
> +	if (!mii_np) {
> +		dev_err(eth->dev, "no %s child node found", "mdio-bus");
> +		return -ENODEV;
> +	}
> +
> +	if (!of_device_is_available(mii_np)) {
> +		ret = -ENODEV;
> +		goto err_put_node;
> +	}

It seems like you end up doing these checks twice. In theory it might
change between the calls, but it is very unlikely? Maybe just keep
node reference returned by of_get_child_by_name() and release it in
mtk_mdio_cleanup()?

Or calculate the divider in mtk_mdio_init() as is, but store it away
in struct mtk_eth, so you don't need to redo all the DT parsing?

	Andrew