Subject: Re: [PATCH net 3/3] net: phy: mscc: enable VSC8501/2 RGMII RX clock

From: "Russell King (Oracle)" <[email-masked]>
Date: Sun, 21 May 2023 18:59:53 +0100

On Sat, May 20, 2023 at 06:06:03PM +0200, David Epping wrote:
> +static int vsc85xx_rgmii_enable_rx_clk(struct phy_device *phydev,
> +				       u32 rgmii_cntl)
> +{
> +	int rc, phy_id;
> +
> +	phy_id = phydev->drv->phy_id & phydev->drv->phy_id_mask;
> +	if (PHY_ID_VSC8501 != phy_id && PHY_ID_VSC8502 != phy_id)
> +		return 0;

As you are accessing the phy_id in the phy_driver struct, isn't it
already true that this will be initialised to constants such as
PHY_ID_VSC8501 or PHY_ID_VSC8502? In which case, why would you need
to mask it with drv->phy_id_mask ?

> +
> +	mutex_lock(&phydev->lock);
> +
> +	rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_2, rgmii_cntl,
> +			      VSC8502_RGMII_RX_CLK_DISABLE, 0);
> +
> +	mutex_unlock(&phydev->lock);

What is the purpose of taking this lock? phy_modify_paged() will do its
read-modify-write access and page accesses under the MDIO bus lock,
which should be all that's required to guarantee an atomic update.

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