Re: [PATCH net-next v2 3/3] net: phy: dp83822: Add support for changing the MAC termination

[Dimitri Fedrau]

Am Fri, Apr 11, 2025 at 10:04:48AM -0500 schrieb Rob Herring:
> On Tue, Apr 08, 2025 at 07:18:31PM +0200, Dimitri Fedrau wrote:
> > On Tue, Apr 08, 2025 at 03:28:32PM +0200, Andrew Lunn wrote:
> > > On Tue, Apr 08, 2025 at 01:01:17PM +0000, Fedrau Dimitri (LED) wrote:
> > > > -----Ursprüngliche Nachricht-----
> > > > Von: Andrew Lunn <andrew@xxxxxxx> 
> > > > Gesendet: Dienstag, 8. April 2025 14:47
> > > > An: Fedrau Dimitri (LED) <dimitri.fedrau@xxxxxxxxxxxx>
> > > > Cc: Heiner Kallweit <hkallweit1@xxxxxxxxx>; Russell King <linux@xxxxxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric Dumazet <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni <pabeni@xxxxxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; Krzysztof Kozlowski <krzk+dt@xxxxxxxxxx>; Conor Dooley <conor+dt@xxxxxxxxxx>; Florian Fainelli <f.fainelli@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Dimitri Fedrau <dima.fedrau@xxxxxxxxx>
> > > > Betreff: Re: [PATCH net-next v2 3/3] net: phy: dp83822: Add support for changing the MAC termination
> > > > 
> > > > > > +static const u32 mac_termination[] = {
> > > > > > +	99, 91, 84, 78, 73, 69, 65, 61, 58, 55, 53, 50, 48, 46, 44, 43,
> > > > > 
> > > > > Please add this list to the binding.
> > > > 
> > > > Add this list to "ti,dp83822.yaml" ?
> > > 
> > > Yes please. Ideally we want the DT validation tools to pick up invalid
> > > values before they reach the kernel.
> > >
> > Ok, but then I would have to add "mac-termination-ohms" property to
> > "ti,dp83822.yaml" as well together with the allowed values ? Ending up in
> > some sort of duplication, because the property is already defined in
> > "ethernet-phy.yaml". Is this the right way to do it ?
> 
> It is not duplication because you are adding constraints. I was thinking 
> the definition in ethernet-phy.yaml should have some logical limit. Say
> 200 ohms as termination resistance is typically 10s of ohms. 
> 
> Seems like a long list to define to me, but if the driver is going to 
> reject unknown values it makes sense. You could also make the driver 
> just pick the closest match rather than require an exact match. 
> Resistance values are nominal anyways.
>
Will add the logical limit into ethernet-phy.yaml and add the table with
the allowed values into ti,dp83822.yaml.