netdev - Re: [PATCH] phy: nxp-c45-tja11xx: add interrupt support

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Date:   Fri, 23 Apr 2021 16:42:29 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "Radu Pirea (NXP OSS)" <radu-nicolae.pirea@....nxp.com>,
        hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] phy: nxp-c45-tja11xx: add interrupt support

On Fri, Apr 23, 2021 at 03:07:51PM +0200, Andrew Lunn wrote:
> > +static irqreturn_t nxp_c45_handle_interrupt(struct phy_device *phydev)
> > +{
> > +	irqreturn_t ret = IRQ_NONE;
> > +	int irq;
> > +
> > +	irq = phy_read_mmd(phydev, MDIO_MMD_VEND1, VEND1_PHY_IRQ_STATUS);
> > +	if (irq & PHY_IRQ_LINK_EVENT) {
> > +		phy_trigger_machine(phydev);
> > +		phy_write_mmd(phydev, MDIO_MMD_VEND1, VEND1_PHY_IRQ_ACK,
> > +			      PHY_IRQ_LINK_EVENT);
> 
> The ordering here is interesting. Could phy_trigger_machine() cause a
> second interrupt? Which you then clear without acting upon before
> exiting the interrupt handler? I think you should ACK the interrupt
> before calling phy_trigger_machine().

I thought that the irqchip driver keeps the interrupt line disabled
until the handler finishes, and that recursive interrupts aren't a thing
in Linux? Even with threaded interrupts, I thought this is what
IRQF_ONESHOT deals with.