netdev - Re: [PATCH net] net: mvpp2: fix condition for setting up link interrupt

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Message-ID: <20191208164235.GT1344@shell.armlinux.org.uk>
Date:   Sun, 8 Dec 2019 16:42:36 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     Willy Tarreau <w@....eu>, Andrew Lunn <andrew@...n.ch>,
        Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        maxime.chevallier@...tlin.com,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: mvpp2: fix condition for setting up link
 interrupt

On Fri, Jan 25, 2019 at 09:37:20AM +0100, Antoine Tenart wrote:
> Hi,
> 
> On Thu, Jan 24, 2019 at 04:07:41PM +0000, Russell King - ARM Linux admin wrote:
> > On Thu, Jan 24, 2019 at 04:51:37PM +0100, Andrew Lunn wrote:
> > > On Thu, Jan 24, 2019 at 02:18:03PM +0100, Thomas Bogendoerfer wrote:
> > > > 
> > > > Fixes: 4bb043262878 ("net: mvpp2: phylink support")
> > > > Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@...e.de>
> > > > ---
> > > >  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 16066c2d5b3a..0fbfe1945a69 100644
> > > > --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > > +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > > @@ -3405,7 +3405,7 @@ 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 && port->phylink) {
> > > >  		err = request_irq(port->link_irq, mvpp2_link_status_isr, 0,
> > > >  				  dev->name, port);
> > > >  		if (err) {
> > 
> > This still looks fishy to me.  mvpp2_link_status_isr() has handling in
> > it that is safe to be called for non-phylink cases, so presumably the
> > right fix is to drop the "&& !port->phylink" completely?
> 
> That's right, mvpp2_link_status_isr() is safe to be called with or
> without phylink being used. This IRQ is reporting the link status, and
> is used when using in-band status or when phylink isn't used.
> 
> We do have a similar fix locally, which looks like:
> 
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index 2bcbf9caaf0d..6bab1824a1e4 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -3406,7 +3406,8 @@ 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 &&
> +           (!port->phylink || !port->has_phy)) {
>                 err = request_irq(port->link_irq, mvpp2_link_status_isr, 0,
>                                   dev->name, port);
>                 if (err) {
> 
> We haven't submitted it yet, as we saw several issues when a port has no
> PHY and is using the XLG MAC (so, not on the mcbin). We currently are
> working on them.
> 
> I don't like to ask this, as you submitted the fix first, but I do think
> we should hold back a bit while we figure out proper solutions. If you
> need in-band status to be working properly, we could share out current
> local branch so you can test and validate it do solve your issue.

Hi Antoine,

Today, I received an email from Willy Tarreau about this issue which
persists to this day with mainline kernels.

Willy reminded me that I've been carrying a fix for this, but because
of your concerns as stated above, I haven't bothered submitting it
through fear of causing regressions (which you seem to know about):

   http://git.armlinux.org.uk/cgit/linux-arm.git/commit/?h=mvpp2&id=67ef3bff255b26cc0d6def8ca99c4e8ae9937727

Just like Thomas' case, the current code is broken for phylink when
in-band negotiation is being used - such as with the 1G/2.5G SFP
slot on the Macchiatobin.

It seems that resolving the issue has stalled.  Can I merge my patch,
or could you state exactly what the problems are with it so that
someone else can look into the issues please?

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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