netdev - Re: [PATCH net-next RFC v4 3/5] dt-bindings: net: phy: add timestamp preferred choice property

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Message-ID: <20230502111043.2e8d48c9@kmaincent-XPS-13-7390>
Date:   Tue, 2 May 2023 11:10:43 +0200
From:   Köry Maincent <kory.maincent@...tlin.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, kuba@...nel.org, glipus@...il.com,
        maxime.chevallier@...tlin.com, vadim.fedorenko@...ux.dev,
        richardcochran@...il.com, gerhard@...leder-embedded.com,
        thomas.petazzoni@...tlin.com, krzysztof.kozlowski+dt@...aro.org,
        robh+dt@...nel.org, linux@...linux.org.uk
Subject: Re: [PATCH net-next RFC v4 3/5] dt-bindings: net: phy: add
 timestamp preferred choice property

On Sat, 29 Apr 2023 20:42:17 +0300
Vladimir Oltean <vladimir.oltean@....com> wrote:

> On Wed, Apr 12, 2023 at 03:44:46PM +0200, Köry Maincent wrote:
> > On Wed, 12 Apr 2023 16:14:21 +0300 Vladimir Oltean
> > <vladimir.oltean@....com> wrote:  
> > > Do we need this device tree functionality?  
> > 
> > I would say so. Expected as I wrote the patch. ;)
> > 
> > My point was that the new behavior to MAC as default timestamping does not
> > fit all the case, especially when a board is designed with PHY like the TI
> > PHYTER which is a far better timestamping choice (according to Richard).
> > The user doesn't need to know this, he wants to have the better time stamp
> > selected by default without any investigation. That's why having devicetree
> > property for that could be useful.  
> 
> The TI PHYTER is the "NatSemi DP83640" entry in the whitelist for PHYs
> that still use their timestamping by default. Can you please come up
> with an example which is actually useful?

If a future PHY, featured like this TI PHYTER, is supported in the future the
default timestamp will be the MAC and we won't be able to select the PHY by
default.
Another example is my case with the 88E151x PHY, on the Russell side with the
Macchiatobin board, the MAC is more precise, and in my side with a custom board
with macb MAC, the PHY is more precise. Be able to select the prefer one from
devicetree is convenient.