linux-kernel - Re: [PATCH net-next v2 2/4] net: stmmac: stm32: add WoL from PHY support

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Message-ID: <aNjwGHrefA5j3dOp@shell.armlinux.org.uk>
Date: Sun, 28 Sep 2025 09:21:44 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Florian Fainelli <florian.fainelli@...adcom.com>
Cc: Gatien Chevallier <gatien.chevallier@...s.st.com>,
	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>, 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 v2 2/4] net: stmmac: stm32: add WoL from PHY
 support

On Fri, Sep 26, 2025 at 12:05:19PM -0700, Florian Fainelli wrote:
> I like the direction this is going, we could probably take one step further
> and extract the logic present in bcmgenet_wol.c and make those helper
> functions for other drivers to get the overlay of PHY+MAC WoL
> options/password consistent across all drivers. What do you think?

The logic I've implemented is fairly similar, but with one difference:
I'm always storing the sopass, which means in the wol_get method I
don't have to be concerned with the sopass returned by the PHY.
This should be fine, unless the PHY was already configured for WoL
magicsecure, and in that case we'll return a zero SOPASS but indicating
WAKE_MAGICSECURE which probably isn't great.

So, my new get_wol logic is:

        if (phylink_mac_supports_wol(pl)) {
                if (phylink_phy_supports_wol(pl, pl->phydev))
                        phy_ethtool_get_wol(pl->phydev, wol);

                /* Where the MAC augments the WoL support, merge its support and
                 * current configuration.
                 */
                if (~wol->wolopts & pl->wolopts_mac & WAKE_MAGICSECURE)
                        memcpy(wol->sopass, pl->wol_sopass,
                               sizeof(wol->sopass));

                wol->supported |= pl->config->wol_mac_support;
                wol->wolopts |= pl->wolopts_mac;

with:

static bool phylink_mac_supports_wol(struct phylink *pl)
{
        return !!pl->mac_ops->mac_wol_set;
}

static bool phylink_phy_supports_wol(struct phylink *pl,
                                     struct phy_device *phydev)
{
        return phydev && (pl->config->wol_phy_legacy || phy_can_wakeup(phydev));
}

static inline bool phy_can_wakeup(struct phy_device *phydev)
{
        return device_can_wakeup(&phydev->mdio.dev);
}

This is to cope with PHYs that respond to phy_ethtool_get_wol()
reporting that they support WoL but have no capability to actually wake
the system up. MACs can choose whether to override that by setting
phylink_config->wol_phy_legacy.

Much like taking this logic away from MAC driver authors, I think we
need to take the logic around "can this PHY actually wake-up the
system" away from the PHY driver author. I believe every driver that
supports WoL with the exception of realtek and broadcom.c reports that
WoL is supported and accepts set_wol() even when they're not capable
of waking the system. e.g. bcm_phy_get_wol():

        wol->supported = BCM54XX_WOL_SUPPORTED_MASK;
        wol->wolopts = 0;

with no prior checks. This is why the "phylink_phy_supports_wol()"
logic above is necessary, otherwise implementing this "use either
the PHY or MAC" logic will break stuff.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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