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

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Date:   Fri, 13 Dec 2019 16:34:03 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Russell King <rmk+kernel@...linux.org.uk>
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 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?

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) {