linux-kernel - Re: [RFC] net: phy: smsc: Disable auto-negotiation on startup

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Message-ID: <20161012150914.aoxvdtrf5gh5z5t4@senary>
Date:   Wed, 12 Oct 2016 10:09:14 -0500
From:   Kyle Roeschley <kyle.roeschley@...com>
To:     Jeremy Linton <jeremy.linton@....com>
CC:     <f.fainelli@...il.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] net: phy: smsc: Disable auto-negotiation on startup

On Tue, Oct 11, 2016 at 09:32:30AM -0500, Jeremy Linton wrote:
> On 10/10/2016 12:41 PM, Kyle Roeschley wrote:
> > Because the SMSC PHY completes auto-negotiation before the driver is
> > ready to handle interrupts, the PHY state machine never realizes that we
> > have a link. Clear the ANENABLE bit on initialization, which lets
> > genphy_config_aneg do its thing when that code is hit later.
> > 
> > While this patch does fix the problem we see (no link on boot without
> > re-plugging the cable), it seems like the generic PHY code should be
> > able to handle auto-negotiation completing before interrupts are
> > enabled. Submitted as an RFC in the hopes that someone has an idea as to
> > how that could be done.
> 
> Hi,
> 
> 	Which smsc chip/driver? Maybe assuring the device interrupts are enabled
> before the phy is started is a solution?
> 
> 	The whole problem sounds similar to what was recently happening in the
> smsc911x driver, but AFAIK that driver is basically only polling at this
> point so connecting the phy before the interrupts are enabled shouldn't be a
> problem.
> 

We're using the SMSC LAN8720A with the Cadence MACB ethernet controller.
Interrupts are enabled before the phy is started, but it looks like the patch
Florian pointed me to (https://www.spinics.net/lists/netdev/msg397857.html)
fixes my interrupt problem.

> > 
> > This fix is copied from commit 99f81afc139c ("phy: micrel: Disable auto
> > negotiation on startup").
> > 
> > Signed-off-by: Kyle Roeschley <kyle.roeschley@...com>
> > ---
> >  drivers/net/phy/smsc.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/net/phy/smsc.c b/drivers/net/phy/smsc.c
> > index b62c4aa..8de8011 100644
> > --- a/drivers/net/phy/smsc.c
> > +++ b/drivers/net/phy/smsc.c
> > @@ -62,6 +62,16 @@ static int smsc_phy_config_init(struct phy_device *phydev)
> >  			return rc;
> >  	}
> > 
> > +	if (phy_interrupt_is_valid(phydev)) {
> > +		rc = phy_read(phydev, MII_BMCR);
> > +		if (rc < 0)
> > +			return rc;
> > +
> > +		rc = phy_write(phydev, MII_BMCR, rc & ~BMCR_ANENABLE);
> > +		if (rc < 0)
> > +			return rc;
> > +	}
> > +
> >  	return smsc_phy_ack_interrupt(phydev);
> >  }
> > 
> > 
> 

-- 
Kyle Roeschley
Software Engineer
National Instruments