netdev - Re: [PATCH] net: phy: Don't disable irqs on shutdown if WoL is enabled

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Date: Thu, 10 Aug 2023 14:01:03 +0300
From: Ioana Ciornei <ioana.ciornei@....com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Uwe Kleine-K├Ânig <u.kleine-koenig@...gutronix.de>,
	Ioana Ciornei <ciorneiioana@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alexandru Ardelean <alexandru.ardelean@...log.com>,
	Andre Edich <andre.edich@...rochip.com>,
	Antoine Tenart <atenart@...nel.org>,
	Baruch Siach <baruch@...s.co.il>,
	Christophe Leroy <christophe.leroy@....fr>,
	Divya Koppera <Divya.Koppera@...rochip.com>,
	Hauke Mehrtens <hauke@...ke-m.de>,
	Jerome Brunet <jbrunet@...libre.com>,
	Kavya Sree Kotagiri <kavyasree.kotagiri@...rochip.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Marco Felsch <m.felsch@...gutronix.de>, Marek Vasut <marex@...x.de>,
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
	Mathias Kresin <dev@...sin.me>, Maxim Kochetkov <fido_max@...ox.ru>,
	Michael Walle <michael@...le.cc>,
	Neil Armstrong <narmstrong@...libre.com>,
	Nisar Sayed <Nisar.Sayed@...rochip.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Philippe Schenker <philippe.schenker@...adex.com>,
	Willy Liu <willy.liu@...ltek.com>,
	Yuiko Oshino <yuiko.oshino@...rochip.com>
Subject: Re: [PATCH] net: phy: Don't disable irqs on shutdown if WoL is
 enabled

On Wed, Aug 09, 2023 at 08:15:27PM +0100, Russell King (Oracle) wrote:
> On Wed, Aug 09, 2023 at 06:21:58PM +0200, Andrew Lunn wrote:
> > > Thinking about this, I wonder whether we could solve your issue by
> > > disabling interrupts when the PHY is probed, rather than disabling
> > > them on shutdown - something like this? (not build tested)
> > > 
> > > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> > > index 3e9909b30938..4d1a37487923 100644
> > > --- a/drivers/net/phy/phy_device.c
> > > +++ b/drivers/net/phy/phy_device.c
> > > @@ -3216,6 +3216,8 @@ static int phy_probe(struct device *dev)
> > >  			goto out;
> > >  	}
> > >  
> > > +        phy_disable_interrupts(phydev);
> > > +
> > >  	/* Start out supporting everything. Eventually,
> > >  	 * a controller will attach, and may modify one
> > >  	 * or both of these values
> > 
> > At some point, the interrupt is going to be enabled again. And then
> > the WoL interrupt will fire. I think some PHY drivers actually need to
> > see that WoL interrupt. e.g. the marvell driver has this comment:
> > 
> > static int m88e1318_set_wol(struct phy_device *phydev,
> >                             struct ethtool_wolinfo *wol)
> > {
> > ....
> >                 /* If WOL event happened once, the LED[2] interrupt pin
> >                  * will not be cleared unless we reading the interrupt status
> >                  * register. If interrupts are in use, the normal interrupt
> >                  * handling will clear the WOL event. Clear the WOL event
> >                  * before enabling it if !phy_interrupt_is_valid()
> >                  */
> > 
> > So it seems like just probing the marvell PHY is not enough to clear
> > the WoL interrupt.
> > 
> > Can we be sure that the other PHY has reached a state it can handle
> > and clear an interrupt when we come to enable the interrupt? I think
> > not, especially in cases like NFS root, where the interface will be
> > put into use as soon as it exists, maybe before the other interface
> > has probed.
> 
> I suppose the question to Ioana would be - are the two AR8031 PHYs on
> the same MDIO bus? If they are, then we're safe, because both will be
> probed consecutively (because they're using the same driver.)
> 

Yes, the two AR8031 PHYs are on the same MDIO bus.

I just tested your approach to disable the interrupts at phy_probe() and
it seems to be working. I also tested with NFS boot using one of the
PHYs and it's behaving ok.

I think I'm ok with this approach as long as Uwe's problem is also
fixed. I don't know how a wake-on-lan procedure works and if it matters
if the WoL interrupt is lost before the PHY driver gets to know about
it.

Ioana