netdev - Re: [RFC net-next 0/5] net: phy: add support for shared interrupts

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Message-ID: <20201024181945.pip6sdal6hpa6fns@skbuf>
Date:   Sat, 24 Oct 2020 18:19:46 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        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>,
        Dan Murphy <dmurphy@...com>,
        Divya Koppera <Divya.Koppera@...rochip.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        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>,
        Philippe Schenker <philippe.schenker@...adex.com>,
        Willy Liu <willy.liu@...ltek.com>,
        Yuiko Oshino <yuiko.oshino@...rochip.com>
Subject: Re: [RFC net-next 0/5] net: phy: add support for shared interrupts

On Sat, Oct 24, 2020 at 07:17:05PM +0200, Andrew Lunn wrote:
> > - Every PHY driver gains a .handle_interrupt() implementation that, for
> >   the most part, would look like below:
> > 
> > 	irq_status = phy_read(phydev, INTR_STATUS);
> > 	if (irq_status < 0) {
> > 		phy_error(phydev);
> > 		return IRQ_NONE;
> > 	}
> > 
> > 	if (irq_status == 0)
> > 		return IRQ_NONE;
> > 
> > 	phy_trigger_machine(phydev);
> > 
> > 	return IRQ_HANDLED;
> 
> Hi Ioana
> 
> It looks like phy_trigger_machine(phydev) could be left in the core,
> phy_interrupt(). It just needs to look at the return code, IRQ_HANDLED
> means trigger the state machine.

I tend to disagree that this would bring us any benefit.

Keeping the phy_trigger_machine() inside the phy_interrupt() would mean
that we are changing the convention of what the implementation of
.handle_interrupt() should do.

At the moment, there are drivers which use it to handle multiple
interrupt sources within the same PHY device (e.g. MACSEC, 1588, link
state). With your suggestion, when a MACSEC interrupt is received, the
PHY driver would be forced to return IRQ_NONE just so phylib does not
trigger the link state machine. I think this would eventually lead to
some "irq X: nobody cared".

Also, the vsc8584_handle_interrupt() already calls a wrapper over
phy_trigger_machine() called phy_mac_interrupt() which was intended for
MAC driver use only.

Ioana