netdev - Re: [PATCH net-next 3/4] net: phy: realtek: use paged access for MDIO_MMD

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Message-ID: <a5a06220-1245-40c8-a80e-151c1f7a0993@oracle.com>
Date: Sun, 4 Jan 2026 20:00:14 +0530
From: ALOK TIWARI <alok.a.tiwari@...cle.com>
To: Daniel Golle <daniel@...rotopia.org>, 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>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Michael Klein <michael@...sekall.de>,
        Aleksander Jan Bajkowski
 <olek2@...pl>,
        Bevan Weiss <bevan.weiss@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 3/4] net: phy: realtek: use paged access for
 MDIO_MMD_VEND2 in C22 mode



On 1/4/2026 6:42 PM, Daniel Golle wrote:
> +static int rtl822xb_read_mmd(struct phy_device *phydev, int devnum, u16 reg)
> +{
> +	int oldpage, ret, read_ret;
> +	u16 page;
> +
> +	/* Use Clause-45 bus access in case it is available */
> +	if (phydev->is_c45)
> +		return __mdiobus_c45_read(phydev->mdio.bus, phydev->mdio.addr,
> +					  devnum, mmdreg);
> +

mmdreg is not defined.

> +	/* Use indirect access via MII_MMD_CTRL and MII_MMD_DATA for all
> +	 * MMDs except MDIO_MMD_VEND2
> +	 */
> +	if (devnum != MDIO_MMD_VEND2) {
> +		__mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
> +				MII_MMD_CTRL, devnum);
> +		__mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
> +				MII_MMD_DATA, mmdreg);
> +		__mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
> +				MII_MMD_CTRL, devnum | MII_MMD_CTRL_NOINCR);
> +
> +		return __mdiobus_read(phydev->mdio.bus, phydev->mdio.addr,
> +				       MII_MMD_DATA);
> +	}
> +
> +	/* Use paged access for MDIO_MMD_VEND2 over Clause-22 */
> +	page = RTL822X_VND2_TO_PAGE(reg);
> +	oldpage = __phy_read(phydev, RTL821x_PAGE_SELECT);
> +	if (oldpage < 0)
> +		return ret;
> +
> +	if (oldpage != page) {
> +		ret = __phy_write(phydev, RTL821x_PAGE_SELECT, page);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	read_ret = __phy_read(phydev, RTL822X_VND2_TO_PAGE_REG(reg));
> +	if (oldpage != page) {
> +		ret = __phy_write(phydev, RTL821x_PAGE_SELECT, oldpage);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return read_ret;
> +}

Thanks,
Alok