netdev - Re: [PATCH net] net: phy: fix IRQ-based wake-on-lan over hibernate / power off

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Message-ID: <e4c4a448-2f3f-4693-bc5e-1d39ad76d233@lunn.ch>
Date: Fri, 11 Aug 2023 16:38:42 +0200
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	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>,
	"David S. Miller" <davem@...emloft.net>,
	Divya Koppera <Divya.Koppera@...rochip.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Hauke Mehrtens <hauke@...ke-m.de>,
	Ioana Ciornei <ioana.ciornei@....com>,
	Jakub Kicinski <kuba@...nel.org>,
	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>,
	Paolo Abeni <pabeni@...hat.com>,
	Philippe Schenker <philippe.schenker@...adex.com>,
	Willy Liu <willy.liu@...ltek.com>,
	Yuiko Oshino <yuiko.oshino@...rochip.com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	netdev@...r.kernel.org
Subject: Re: [PATCH net] net: phy: fix IRQ-based wake-on-lan over hibernate /
 power off

On Fri, Aug 11, 2023 at 11:26:30AM +0100, Russell King (Oracle) wrote:
> Uwe reports:
> "Most PHYs signal WoL using an interrupt. So disabling interrupts [at
> shutdown] breaks WoL at least on PHYs covered by the marvell driver."
> 
> Discussing with Ioana, the problem which was trying to be solved was:
> "The board in question is a LS1021ATSN which has two AR8031 PHYs that
> share an interrupt line. In case only one of the PHYs is probed and
> there are pending interrupts on the PHY#2 an IRQ storm will happen
> since there is no entity to clear the interrupt from PHY#2's registers.
> PHY#1's driver will get stuck in .handle_interrupt() indefinitely."
> 
> Further confirmation that "the two AR8031 PHYs are on the same MDIO
> bus."
> 
> With WoL using interrupts to wake the system, in such a case, the
> system will begin booting with an asserted interrupt. Thus, we need to
> cope with an interrupt asserted during boot.
> 
> Solve this instead by disabling interrupts during PHY probe. This will
> ensure in Ioana's situation that both PHYs of the same type sharing an
> interrupt line on a common MDIO bus will have their interrupt outputs
> disabled when the driver probes the device, but before we hook in any
> interrupt handlers - thus avoiding the interrupt storm.
> 
> A better fix would be for platform firmware to disable the interrupting
> devices at source during boot, before control is handed to the kernel.
> 
> Fixes: e2f016cf7751 ("net: phy: add a shutdown procedure")
> Link: 20230804071757.383971-1-u.kleine-koenig@...gutronix.de
> Reported-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew