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

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Message-ID: <20190301111344.GB3554@kwain>
Date:   Fri, 1 Mar 2019 12:13:44 +0100
From:   Antoine Tenart <antoine.tenart@...tlin.com>
To:     Russell King <rmk+kernel@...linux.org.uk>
Cc:     Antoine Tenart <antoine.tenart@...tlin.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Baruch Siach <baruch@...s.co.il>,
        Sven Auhagen <sven.auhagen@...eatech.de>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH RFC] net: marvell: mvpp2: phylink requires the link
 interrupt

Hi Russell,

I've been using this patch on my local branch for the past 3 weeks, and
I saw no obvious issue so far. (I also used a similar patch before).

Do you have pending questions regarding this patch? Otherwise I think
you can sent it again without the RFC tag, with my Tested-by and/or
Acked-by tags if you want.

Thanks!
Antoine

On Fri, Feb 08, 2019 at 03:39:10PM +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>
> Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> ---
> This is the final patch that I mentioned in the cover letter
>    "[PATCH net-next 0/5] mvpp2 phylink fixes"
> 
>  drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index 93fed4080dbf..0b164b424dca 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -3412,7 +3412,7 @@ 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) {
> -- 
> 2.7.4
> 

-- 
Antoine Ténart, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com