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Date:   Wed, 9 Aug 2023 18:21:58 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc:     Ioana Ciornei <ioana.ciornei@nxp.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
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        <u.kleine-koenig@pengutronix.de>,
        Ioana Ciornei <ciorneiioana@gmail.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Alexandru Ardelean <alexandru.ardelean@analog.com>,
        Andre Edich <andre.edich@microchip.com>,
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        Yuiko Oshino <yuiko.oshino@microchip.com>
Subject: Re: [PATCH] net: phy: Don't disable irqs on shutdown if WoL is
 enabled
Message-ID: <2f717c52-0ae5-4702-ab34-7ce0bffe8c86@lunn.ch>
References: <20230804071757.383971-1-u.kleine-koenig@pengutronix.de>
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 <1e438a02-6964-ce65-5584-e8ea57a694bb@gmail.com>
 <ZNLIOEBXNgPOnFSf@shell.armlinux.org.uk>
 <20230809142155.4dtmnmmecaycbtum@LXL00007.wbi.nxp.com>
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 <20230809154418.hjkf43ndwfzretiy@LXL00007.wbi.nxp.com>
 <ZNO4RwYzZYUTu1uk@shell.armlinux.org.uk>
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> 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.

	Andrew