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

[Florian Fainelli <f.fainelli@gmail.com>]

On 8/11/23 03:26, 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@pengutronix.de
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
-- 
Florian