linux-kernel - RE: [PATCH v1] net: phy: adin: Add flags to disable enhanced link detection

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Date:   Tue, 28 Feb 2023 15:13:59 +0000
From:   Ken Sloat <ken.s@...iscite.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Michael Hennerich <michael.hennerich@...log.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ken Sloat <ken.s@...iscite.com>
Subject: RE: [PATCH v1] net: phy: adin: Add flags to disable enhanced link
 detection

Hi Andrew,

Thanks for your quick reply!

> -----Original Message-----
> From: Andrew Lunn <andrew@...n.ch>
> Sent: Tuesday, February 28, 2023 9:53 AM
> To: Ken Sloat <ken.s@...iscite.com>
> Cc: Michael Hennerich <michael.hennerich@...log.com>; Heiner Kallweit
> <hkallweit1@...il.com>; Russell King <linux@...linux.org.uk>; David S.
> Miller <davem@...emloft.net>; Jakub Kicinski <kuba@...nel.org>;
> netdev@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v1] net: phy: adin: Add flags to disable enhanced link
> detection
> 
> On Tue, Feb 28, 2023 at 09:40:56AM -0500, Ken Sloat wrote:
> > Enhanced link detection is an ADI PHY feature that allows for earlier
> > detection of link down if certain signal conditions are met. This
> > feature is for the most part enabled by default on the PHY. This is
> > not suitable for all applications and breaks the IEEE standard as
> > explained in the ADI datasheet.
> >
> > To fix this, add override flags to disable enhanced link detection for
> > 1000BASE-T and 100BASE-TX respectively by clearing any related feature
> > enable bits.
> >
> > This new feature was tested on an ADIN1300 but according to the
> > datasheet applies equally for 100BASE-TX on the ADIN1200.
> >
> > Signed-off-by: Ken Sloat <ken.s@...iscite.com>
> Hi Ken
> 
> > +static int adin_config_fld_en(struct phy_device *phydev)
> 
> Could we have a better name please. I guess it means Fast Link Down, but
> the commit messages talks about Enhanced link detection. This function is
> also not enabling fast link down, but disabling it, so _en seems wrong.
> 
"Enhanced Link Detection" is the ADI term, but the associated register for controlling this feature is called "FLD_EN." I considered "ELD" as that makes more sense language wise but it did not match the datasheet and did not want to invent a new term. I was not sure what the F was but perhaps you are right, as the link is brought down as part of this feature when conditions are met. I am guessing then that this FLD is a carryover from some initial name of the feature that was later re-branded.

I am happy to change fld -> eld or something else that might make more sense for users and am open to any suggestions.

> > +{
> > +	struct device *dev = &phydev->mdio.dev;
> > +	int reg;
> > +
> > +	reg = phy_read_mmd(phydev, MDIO_MMD_VEND1,
> ADIN1300_FLD_EN_REG);
> > +	if (reg < 0)
> > +		return reg;
> > +
> > +	if (device_property_read_bool(dev, "adi,disable-fld-1000base-t"))
> 
> You need to document these two properties in the device tree binding.
> 

I already have a separate patch for this. I will send both patches when I re-submit and CC additional parties.

> Please also take a read of
> https://www.kernel.org/doc/html/latest/process/maintainer-
> netdev.html#netdev-faq
> 
>     Andrew

Sincerely,
Ken Sloat