linux-kernel - Re: [PATCH net-next 3/4] drivers/net/phy: Add driver for the onsemi NCN26000 10BASE-T1S PHY

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Message-ID: <Y4z/A5Yn39AX0yWm@gvm01>
Date:   Sun, 4 Dec 2022 21:11:47 +0100
From:   Piergiorgio Beruto <piergiorgio.beruto@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, Oleksij Rempel <o.rempel@...gutronix.de>
Subject: Re: [PATCH net-next 3/4] drivers/net/phy: Add driver for the onsemi
 NCN26000 10BASE-T1S PHY

On Sun, Dec 04, 2022 at 07:00:38PM +0100, Andrew Lunn wrote:
> > On Sun, Dec 04, 2022 at 03:31:33AM +0100, Piergiorgio Beruto wrote:
> > > +static irqreturn_t ncn26000_handle_interrupt(struct phy_device *phydev)
> > > +{
> > > +	const struct ncn26000_priv *const priv = phydev->priv;
> > > +	u16 events;
> > > +	int ret;
> > > +
> > > +	// read and aknowledge the IRQ status register
> > > +	ret = phy_read(phydev, NCN26000_REG_IRQ_STATUS);
> > > +
> > > +	if (unlikely(ret < 0))
> > > +		return IRQ_NONE;
> > > +
> > > +	events = (u16)ret & priv->enabled_irqs;
> > > +	if (events == 0)
> > > +		return IRQ_NONE;
> > > +
> > > +	if (events & NCN26000_IRQ_LINKST_BIT) {
> > > +		ret = phy_read(phydev, MII_BMSR);
> > > +
> > > +		if (unlikely(ret < 0)) {
> > > +			phydev_err(phydev,
> > > +				   "error reading the status register (%d)\n",
> > > +				   ret);
> > > +
> > > +			return IRQ_NONE;
> > > +		}
> > > +
> > > +		phydev->link = ((u16)ret & BMSR_ANEGCOMPLETE) ? 1 : 0;
> 
> Hi Piergiorgio
> 
> Interrupt handling in PHY don't follow the usual model. Historically,
> PHYs were always polled once per second. The read_status() function
> gets called to report the current status of the PHY. Interrupt are
> just used to indicate that poll should happen now. All the handler
> needs to do is clear the interrupt line so it can be safely reenabled
> and not cause an interrupt storm, and call phy_trigger_machine() to
> trigger the poll.
To be honest, I sort of realized that. But I was confused again by the
read_status() function description. It looked to me it was not invoked
when AN is not supported, but I'm hearing this is not the case.
I'll rework this part.

Thanks
Piergiorgio