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Message-ID: <aNbUdweqsCKAKJKl@shell.armlinux.org.uk>
Date: Fri, 26 Sep 2025 18:59:19 +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 v2 2/4] net: stmmac: stm32: add WoL from PHY
support
On Wed, Sep 17, 2025 at 05:31:16PM +0100, Russell King (Oracle) wrote:
> On Wed, Sep 17, 2025 at 05:36:37PM +0200, Gatien Chevallier wrote:
> > If the "st,phy-wol" property is present in the device tree node,
> > set the STMMAC_FLAG_USE_PHY_WOL flag to use the WoL capability of
> > the PHY.
> >
> > Signed-off-by: Gatien Chevallier <gatien.chevallier@...s.st.com>
> > ---
> > drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> > index 77a04c4579c9dbae886a0b387f69610a932b7b9e..6f197789cc2e8018d6959158b795e4bca46869c5 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> > @@ -106,6 +106,7 @@ struct stm32_dwmac {
> > u32 speed;
> > const struct stm32_ops *ops;
> > struct device *dev;
> > + bool phy_wol;
> > };
> >
> > struct stm32_ops {
> > @@ -433,6 +434,8 @@ static int stm32_dwmac_parse_data(struct stm32_dwmac *dwmac,
> > }
> > }
> >
> > + dwmac->phy_wol = of_property_read_bool(np, "st,phy-wol");
> > +
> > return err;
> > }
> >
> > @@ -557,6 +560,8 @@ static int stm32_dwmac_probe(struct platform_device *pdev)
> > plat_dat->bsp_priv = dwmac;
> > plat_dat->suspend = stm32_dwmac_suspend;
> > plat_dat->resume = stm32_dwmac_resume;
> > + if (dwmac->phy_wol)
> > + plat_dat->flags |= STMMAC_FLAG_USE_PHY_WOL;
>
> I would much rather we found a different approach, rather than adding
> custom per-driver DT properties to figure this out.
>
> Andrew has previously suggested that MAC drivers should ask the PHY
> whether WoL is supported, but this pre-supposes that PHY drivers are
> coded correctly to only report WoL capabilities if they are really
> capable of waking the system. As shown in your smsc PHY driver patch,
> this may not be the case.
>
> Given that we have historically had PHY drivers reporting WoL
> capabilities without being able to wake the system, we can't
> implement Andrew's suggestion easily.
>
> The only approach I can think that would allow us to transition is
> to add:
>
> static inline bool phy_can_wakeup(struct phy_device *phy_dev)
> {
> return device_can_wakeup(&phy_dev->mdio.dev);
> }
>
> to include/linux/phy.h, and a corresponding wrapper for phylink.
> This can then be used to determine whether to attempt to use PHY-based
> Wol in stmmac_get_wol() and rtl8211f_set_wol(), falling back to
> PMT-based WoL if supported at the MAC.
>
> So, maybe something like:
>
> static u32 stmmac_wol_support(struct stmmac_priv *priv)
> {
> u32 support = 0;
>
> if (priv->plat->pmt && device_can_wakeup(priv->device)) {
> support = WAKE_UCAST;
> if (priv->hw_cap_support && priv->dma_cap.pmt_magic_frame)
> support |= WAKE_MAGIC;
> }
>
> return support;
> }
>
> static void stmmac_get_wol(struct net_device *dev, struct ethtool_wolinfo *wol)
> {
> struct stmmac_priv *priv = netdev_priv(dev);
> int err;
>
> /* Check STMMAC_FLAG_USE_PHY_WOL for legacy */
> if (phylink_can_wakeup(priv->phylink) ||
> priv->plat->flags & STMMAC_FLAG_USE_PHY_WOL) {
> err = phylink_ethtool_get_wol(priv->phylink, wol);
> if (err != 0 && err != -EOPNOTSUPP)
> return;
> }
>
> wol->supported |= stmmac_wol_support(priv);
>
> /* A read of priv->wolopts is single-copy atomic. Locking
> * doesn't add any benefit.
> */
> wol->wolopts |= priv->wolopts;
> }
>
> static int stmmac_set_wol(struct net_device *dev, struct ethtool_wolinfo *wol)
> {
> struct stmmac_priv *priv = netdev_priv(dev);
> u32 support, wolopts;
> int err;
>
> wolopts = wol->wolopts;
>
> /* Check STMMAC_FLAG_USE_PHY_WOL for legacy */
> if (phylink_can_wakeup(priv->phylink) ||
> priv->plat->flags & STMMAC_FLAG_USE_PHY_WOL) {
> struct ethtool_wolinfo w;
>
> err = phylink_ethtool_set_wol(priv->phylink, wol);
> if (err != -EOPNOTSUPP)
> return err;
>
> /* Remove the WoL modes that the PHY is handling */
> if (!phylink_ethtool_get_wol(priv->phylink, &w))
> wolopts &= ~w.wolopts;
> }
>
> support = stmmac_wol_support(priv);
>
> mutex_lock(&priv->lock);
> priv->wolopts = wolopts & support;
> device_set_wakeup_enable(priv->device, !!priv->wolopts);
> mutex_unlock(&priv->lock);
>
> return 0;
> }
>
> ... and now I'm wondering whether this complexity is something that
> phylink should handle internally, presenting a mac_set_wol() method
> to configure the MAC-side WoL settings. What makes it difficult to
> just move into phylink is the STMMAC_FLAG_USE_PHY_WOL flag, but
> that could be a "force_phy_wol" flag in struct phylink_config as
> a transitionary measure... so long as PHY drivers get fixed.
I came up with this as an experiment - I haven't tested it beyond
running it through the compiler (didn't let it get to the link stage
yet.) Haven't even done anything with it for stmmac yet.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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View attachment "0001-net-phy-add-phy_can_wakeup.patch" of type "text/x-diff" (1199 bytes)
View attachment "0002-net-phylink-add-Wake-on-Lan-MAC-support.patch" of type "text/x-diff" (5412 bytes)
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