Re: [PATCH v1] net: phy: adin: Add flags to disable enhanced link detection

[Andrew Lunn]

On Tue, Feb 28, 2023 at 03:13:59PM +0000, Ken Sloat wrote:
> Hi Andrew,
> 
> Thanks for your quick reply!
> 
> > -----Original Message-----
> > From: Andrew Lunn <andrew@xxxxxxx>
> > Sent: Tuesday, February 28, 2023 9:53 AM
> > To: Ken Sloat <ken.s@xxxxxxxxxxxxx>
> > Cc: Michael Hennerich <michael.hennerich@xxxxxxxxxx>; Heiner Kallweit
> > <hkallweit1@xxxxxxxxx>; Russell King <linux@xxxxxxxxxxxxxxx>; David S.
> > Miller <davem@xxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>;
> > netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > 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@xxxxxxxxxxxxx>
> > 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.

The Marvell PHYs also support a fast link down mode, so i think using
fast link down everywhere, in the code and the commit message would be
good. How about adin_fast_down_disable().

> > 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.

It is normal to submit them together as a patch set. What generally
happens is that the DT maintainers ACK the documentation patch, and
then it gets merged via the netdev tree.

   Andrew