netdev - Re: [PATCH] net: marvell: mvpp2: phylink requires the link interrupt

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Date:   Sat, 14 Dec 2019 07:56:02 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Willy Tarreau <w@....eu>, Andrew Lunn <andrew@...n.ch>,
        Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        maxime.chevallier@...tlin.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] net: marvell: mvpp2: phylink requires the link interrupt

On Sat, Dec 14, 2019 at 07:51:27AM +0000, Russell King - ARM Linux admin wrote:
> On Fri, Dec 13, 2019 at 04:34:03PM -0800, Jakub Kicinski wrote:
> > On Tue, 10 Dec 2019 22:33:05 +0000, Russell King wrote:
> > > phylink requires the MAC to report when its link status changes when
> > > operating in inband modes.  Failure to report link status changes
> > > means that phylink has no idea when the link events happen, which
> > > results in either the network interface's carrier remaining up or
> > > remaining permanently down.
> > > 
> > > For example, with a fiber module, if the interface is brought up and
> > > link is initially established, taking the link down at the far end
> > > will cut the optical power.  The SFP module's LOS asserts, we
> > > deactivate the link, and the network interface reports no carrier.
> > > 
> > > When the far end is brought back up, the SFP module's LOS deasserts,
> > > but the MAC may be slower to establish link.  If this happens (which
> > > in my tests is a certainty) then phylink never hears that the MAC
> > > has established link with the far end, and the network interface is
> > > stuck reporting no carrier.  This means the interface is
> > > non-functional.
> > > 
> > > Avoiding the link interrupt when we have phylink is basically not
> > > an option, so remove the !port->phylink from the test.
> > > 
> > > Tested-by: Sven Auhagen <sven.auhagen@...eatech.de>
> > > Tested-by: Antoine Tenart <antoine.tenart@...tlin.com>
> > > Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> > 
> > Fixes: 4bb043262878 ("net: mvpp2: phylink support") ?
> > 
> > Seems like you maybe didn't want this backported to stable hence 
> > no fixes tag?
> 
> Correct, because backporting just this patch will break the
> Macchiatobin.
> 
> This patch is dependent on the previous two patches, which are more
> about correct use of the API.  I suspect if you try to backport the
> series, things will get very hairly very quickly.

Oh, sorry, too early, wrong patch.  Yes, please add the fixes tag.

> 
> > 
> > Please advise :)
> > 
> > > diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > index 111b3b8239e1..ef44c6979a31 100644
> > > --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > @@ -3674,7 +3674,7 @@ static int mvpp2_open(struct net_device *dev)
> > >  		valid = true;
> > >  	}
> > >  
> > > -	if (priv->hw_version == MVPP22 && port->link_irq && !port->phylink) {
> > > +	if (priv->hw_version == MVPP22 && port->link_irq) {
> > >  		err = request_irq(port->link_irq, mvpp2_link_status_isr, 0,
> > >  				  dev->name, port);
> > >  		if (err) {
> > 
> > 
> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> According to speedtest.net: 11.9Mbps down 500kbps up

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up