linux-kernel - Re: [PATCH net-next 3/4] net: phy: smsc: fix and improve WoL support

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Message-ID: <aH4kVBTxd4zRYv2l@shell.armlinux.org.uk>
Date: Mon, 21 Jul 2025 12:28:20 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Gatien Chevallier <gatien.chevallier@...s.st.com>
Cc: 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>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Christophe Roullier <christophe.roullier@...s.st.com>,
	Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Simon Horman <horms@...nel.org>,
	Tristram Ha <Tristram.Ha@...rochip.com>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 3/4] net: phy: smsc: fix and improve WoL support

On Mon, Jul 21, 2025 at 01:14:45PM +0200, Gatien Chevallier wrote:
> +static int smsc_phy_suspend(struct phy_device *phydev)
> +{
> +	if (!phydev->wol_enabled)
> +		return genphy_suspend(phydev);

This should not be necessary. Take a look at phy_suspend(). Notice:

        phydev->wol_enabled = phy_drv_wol_enabled(phydev) ||
                              (netdev && netdev->ethtool->wol_enabled);
        /* If the device has WOL enabled, we cannot suspend the PHY */
        if (phydev->wol_enabled && !(phydrv->flags & PHY_ALWAYS_CALL_SUSPEND))
                return -EBUSY;

PHY_ALWAYS_CALL_SUSPEND is not set for this PHY, therefore if
phydev->wol_enabled is set by the above code, phydrv->suspend will
not be called.

> +
> +	return 0;
> +}
> +
> +static int smsc_phy_resume(struct phy_device *phydev)
> +{
> +	int rc;
> +
> +	if (!phydev->wol_enabled)
> +		return genphy_resume(phydev);
> +
> +	rc = phy_read_mmd(phydev, MDIO_MMD_PCS, MII_LAN874X_PHY_MMD_WOL_WUCSR);
> +	if (rc < 0)
> +		return rc;
> +
> +	if (!(rc & MII_LAN874X_PHY_WOL_STATUS_MASK))
> +		return 0;
> +
> +	dev_info(&phydev->mdio.dev, "Woke up from LAN event.\n");
> +	rc = phy_write_mmd(phydev, MDIO_MMD_PCS, MII_LAN874X_PHY_MMD_WOL_WUCSR,
> +			   rc | MII_LAN874X_PHY_WOL_STATUS_MASK);
> +
> +	return rc;

Note that this will be called multiple times, e.g. during attachment of
the PHY to the network device, when the device is opened, etc even
without ->suspend having been called, and before ->wol_enabled has
been set. Make sure your code is safe for this.

-- 
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