netdev - Re: [PATCH net 2/2] net: phy: Use C45 Helpers in PHY

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Date:   Mon, 4 Mar 2019 16:44:55 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Jose Abreu <jose.abreu@...opsys.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Joao Pinto <joao.pinto@...opsys.com>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net 2/2] net: phy: Use C45 Helpers in PHY_FORCING state

On Mon, Mar 04, 2019 at 03:07:24PM +0000, Jose Abreu wrote:
> Hi Andrew,
> 
> On 3/1/2019 1:53 PM, Andrew Lunn wrote:
> > On Fri, Mar 01, 2019 at 11:54:24AM +0100, Jose Abreu wrote:
> >> +static inline int phy_update_link(struct phy_device *phydev)
> >> +{
> >> +	if (!phydev->drv)
> >> +		return -EIO;
> >> +
> >> +	if (phydev->drv->read_status)
> >> +		return phydev->drv->read_status(phydev);
> >> +	else if (phydev->is_c45)
> >> +		return gen10g_read_status(phydev);
> >> +	else
> >> +		return genphy_update_link(phydev);
> >> +}
> > 
> > Hi Jose
> > 
> > The asymmetry here could be an issue.  We might fall into the trap
> > that a c45 PHY has the full state in phydev updated, were as a c22
> > only has the link updated. Somebody testing on C45 might miss a bug
> > for a C22 device.
> 
> Notice that this phy_update_link() is called from PHY_FORCING
> state which in my case happens when autoneg is not enabled / is
> not supported.
> 
> I think it makes sense, in this case, to only update link status,
> no ?
 
Hi Jose

It is actually quite difficult to determine when the link is up. I
personally would not trust gen10g_read_status() to get this right, and
would always implement the read_status callback.

Which PHY driver are you using, which does not support
read_status(). All the mainline PHY drivers do seem to have
read_status implemented.

    Andrew