netdev - Re: [PATCH net-next v3 5/7] usbnet: smsc95xx: Forward PHY interrupts to PHY driver to avoid polling

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Message-ID: <YozJqD5bhg31gjz7@lunn.ch>
Date:   Tue, 24 May 2022 14:03:52 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Lukas Wunner <lukas@...ner.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org,
        Steve Glendinning <steve.glendinning@...well.net>,
        UNGLinuxDriver@...rochip.com, Oliver Neukum <oneukum@...e.com>,
        Andre Edich <andre.edich@...rochip.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Martyn Welch <martyn.welch@...labora.com>,
        Gabriel Hojda <ghojda@...urs.ro>,
        Christoph Fritz <chf.fritz@...glemail.com>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        Philipp Rosenberger <p.rosenberger@...bus.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Ferry Toth <fntoth@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        'Linux Samsung SOC' <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH net-next v3 5/7] usbnet: smsc95xx: Forward PHY interrupts
 to PHY driver to avoid polling

On Tue, May 24, 2022 at 08:16:23AM +0200, Marek Szyprowski wrote:
> On 24.05.2022 03:08, Andrew Lunn wrote:
> >> @@ -976,6 +977,25 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
> >>   	struct phy_driver *drv = phydev->drv;
> >>   	irqreturn_t ret;
> >>   
> >> +	if (IS_ENABLED(CONFIG_PM_SLEEP) &&
> >> +	    (phydev->mdio.dev.power.is_prepared ||
> >> +	     phydev->mdio.dev.power.is_suspended)) {
> >> +		struct net_device *netdev = phydev->attached_dev;
> >> +
> >> +		if (netdev) {
> >> +			struct device *parent = netdev->dev.parent;
> >> +
> >> +			if (netdev->wol_enabled)
> >> +				pm_system_wakeup();
> >> +			else if (device_may_wakeup(&netdev->dev))
> >> +				pm_wakeup_dev_event(&netdev->dev, 0, true);
> >> +			else if (parent && device_may_wakeup(parent))
> >> +				pm_wakeup_dev_event(parent, 0, true);
> >> +		}
> >> +
> >> +		return IRQ_HANDLED;
> > I'm not sure you can just throw the interrupt away. There have been
> > issues with WoL, where the WoL signal has been applied to a PMC, not
> > an actual interrupt. Yet the PHY driver assumes it is an
> > interrupt. And in order for WoL to work correctly, it needs the
> > interrupt handler to be called. We said the hardware is broken, WoL
> > cannot work for that setup.
> >
> > Here you have correct hardware, but you are throwing the interrupt
> > away, which will have the same result. So i think you need to abort
> > the suspend, get the bus working again, and call the interrupt
> > handler. If this is a WoL interrupt you are supposed to be waking up
> > anyway.
> 
> This hardware doesn't support wake-on-lan. It looks somehow that it 
> manages to throw an interrupt just a moment before the power regulator 
> for the whole usb bus is cut off.

Your hardware might not support WOL, but this is generic code. It
needs to work for all hardware.

As for this hardware, if it does not support WOL, why are interrupts
still enabled?

      Andrew