linux-kernel - Re: [net: PATCH] net: mvpp2: disable link IRQ waiting for IDLE frames

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Date:   Tue, 23 Apr 2019 18:08:00 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        netdev <netdev@...r.kernel.org>,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>,
        Grégory Clement <gregory.clement@...tlin.com>,
        nadavh@...vell.com,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Stefan Chulski <stefanc@...vell.com>
Subject: Re: [net: PATCH] net: mvpp2: disable link IRQ waiting for IDLE frames

Hi David, Rusell,

czw., 28 lut 2019 o 14:58 Marcin Wojtas <mw@...ihalf.com> napisał(a):
>
> Hi Russell,
>
> czw., 28 lut 2019 o 10:36 Russell King - ARM Linux admin
> <linux@...linux.org.uk> napisał(a):
> >
> > On Wed, Feb 27, 2019 at 06:47:32PM +0100, Marcin Wojtas wrote:
> > > Current version of the driver was configuring XLG MAC
> > > in a way to wait 3 IDLE frames before allowing for the
> > > link-up interrupt to be triggered. This resulted in an
> > > issue, preventing to detect the link change during RX
> > > traffic on the interface. Fix that.
> >
> > What about noise sensitivity?  Does this now mean that on boards such as
> > Macchiatobin Single Shot or Clearfog GT9k where the serdes is connected
> > directly to a SFP cage, that noise on the serdes lines triggers a link
> > indication?
> >
>
> Afaik waiting for idle frames is not required by any standard. In fact
> this feature of the XLG MAC caused a risk that after dropping the link
> during data transfer it would never go up again until remote peer
> stops it.
>
> I tested it on 3 different boards with SerDes directly connected to
> the SFP cage and I'm also not aware of any reporte about
> noise-triggered false link interrupts in XLG MAC (proprietary Marvell
> mvpp2x driver did not use waiting 3 idle frames feature). I'd rather
> assume the MAC is not vulnerable to it, and only properly established
> link can trigger an event.
>

This patch seems to get forgotten - any objections to merge it?

Best regards,
Marcin

> Best regards,
> Marcin
>
> > >
> > > Fixes: 4bb043262878 ("net: mvpp2: phylink support")
> > > Signed-off-by: Marcin Wojtas <mw@...ihalf.com>
> > > ---
> > >  drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 3 +--
> > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > index 16066c2..f1378f9 100644
> > > --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > > @@ -4532,8 +4532,7 @@ static void mvpp2_xlg_config(struct mvpp2_port *port, unsigned int mode,
> > >               ctrl0 |= MVPP22_XLG_CTRL0_RX_FLOW_CTRL_EN;
> > >
> > >       ctrl4 &= ~MVPP22_XLG_CTRL4_MACMODSELECT_GMAC;
> > > -     ctrl4 |= MVPP22_XLG_CTRL4_FWD_FC | MVPP22_XLG_CTRL4_FWD_PFC |
> > > -              MVPP22_XLG_CTRL4_EN_IDLE_CHECK;
> > > +     ctrl4 |= MVPP22_XLG_CTRL4_FWD_FC | MVPP22_XLG_CTRL4_FWD_PFC;
> > >
> > >       writel(ctrl0, port->base + MVPP22_XLG_CTRL0_REG);
> > >       writel(ctrl4, port->base + MVPP22_XLG_CTRL4_REG);
> > > --
> > > 2.7.4
> > >
> > >
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > >
> >
> > --
> > 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

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