Add "adi,low-cmode-impedance" boolean property which, when present,
configures the PHY for the lowest common-mode impedance on the receive
pair for 100BASE-TX operation.

Signed-off-by: Osose Itua <osose.itua@savoirfairelinux.com>
---
 Documentation/devicetree/bindings/net/adi,adin.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/adi,adin.yaml b/Documentation/devicetree/bindings/net/adi,adin.yaml
index c425a9f1886d..d3c8c5cc4bb1 100644
--- a/Documentation/devicetree/bindings/net/adi,adin.yaml
+++ b/Documentation/devicetree/bindings/net/adi,adin.yaml
@@ -52,6 +52,12 @@ properties:
     description: Enable 25MHz reference clock output on CLK25_REF pin.
     type: boolean
 
+  adi,low-cmode-impedance:
+    description: |
+      Ability to configure for the lowest common-mode impedance on the
+      receive pair for 100BASE-TX.
+    type: boolean
+
 unevaluatedProperties: false
 
 examples:

On Mon, Dec 22, 2025 at 05:21:05PM -0500, Osose Itua wrote:
> Add "adi,low-cmode-impedance" boolean property which, when present,
> configures the PHY for the lowest common-mode impedance on the receive
> pair for 100BASE-TX operation.
> 
> Signed-off-by: Osose Itua <osose.itua@savoirfairelinux.com>
> ---
>  Documentation/devicetree/bindings/net/adi,adin.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/adi,adin.yaml b/Documentation/devicetree/bindings/net/adi,adin.yaml
> index c425a9f1886d..d3c8c5cc4bb1 100644
> --- a/Documentation/devicetree/bindings/net/adi,adin.yaml
> +++ b/Documentation/devicetree/bindings/net/adi,adin.yaml
> @@ -52,6 +52,12 @@ properties:
>      description: Enable 25MHz reference clock output on CLK25_REF pin.
>      type: boolean
>  
> +  adi,low-cmode-impedance:
> +    description: |
> +      Ability to configure for the lowest common-mode impedance on the

Either this is ability or you configure the PHY, as written in commit
msg. The latter suggests that's a SW property, not hardware, thus not
for bindings.

If the first, then why it is not implied by PHY itself - the compatible
(which is missing which makes this binding not selectable).

Best regards,
Krzysztof

On Sat, 2025-12-27 at 13:29 +0100, Krzysztof Kozlowski wrote:
> On Mon, Dec 22, 2025 at 05:21:05PM -0500, Osose Itua wrote:
> > Add "adi,low-cmode-impedance" boolean property which, when present,
> > configures the PHY for the lowest common-mode impedance on the receive
> > pair for 100BASE-TX operation.
> > 
> > Signed-off-by: Osose Itua <osose.itua@savoirfairelinux.com>
> > ---
> >  Documentation/devicetree/bindings/net/adi,adin.yaml | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/adi,adin.yaml
> > b/Documentation/devicetree/bindings/net/adi,adin.yaml
> > index c425a9f1886d..d3c8c5cc4bb1 100644
> > --- a/Documentation/devicetree/bindings/net/adi,adin.yaml
> > +++ b/Documentation/devicetree/bindings/net/adi,adin.yaml
> > @@ -52,6 +52,12 @@ properties:
> >      description: Enable 25MHz reference clock output on CLK25_REF pin.
> >      type: boolean
> >  
> > +  adi,low-cmode-impedance:
> > +    description: |
> > +      Ability to configure for the lowest common-mode impedance on the
> 
> Either this is ability or you configure the PHY, as written in commit
> msg. The latter suggests that's a SW property, not hardware, thus not
> for bindings.
> 

Looking at the datasheet this looks like a system level decision. With the above
it seems we'll actually use more power and it is suited for designs where there is
common-mode noise reaching the phy. So it feels like something we would put in DT... 

But I agree the commit message (and maybe the property description) should
be better in reflecting why this is used rather than just saying what are we enabling.

- Nuno Sá

On Mon, Dec 22, 2025 at 05:21:05PM -0500, Osose Itua wrote:
> Add "adi,low-cmode-impedance" boolean property which, when present,
> configures the PHY for the lowest common-mode impedance on the receive
> pair for 100BASE-TX operation.

FYI: The DT Maintainers prefer that binding patches come first in a
patchset.

> diff --git a/Documentation/devicetree/bindings/net/adi,adin.yaml b/Documentation/devicetree/bindings/net/adi,adin.yaml
> index c425a9f1886d..d3c8c5cc4bb1 100644
> --- a/Documentation/devicetree/bindings/net/adi,adin.yaml
> +++ b/Documentation/devicetree/bindings/net/adi,adin.yaml
> @@ -52,6 +52,12 @@ properties:
>      description: Enable 25MHz reference clock output on CLK25_REF pin.
>      type: boolean
>  
> +  adi,low-cmode-impedance:
> +    description: |
> +      Ability to configure for the lowest common-mode impedance on the
> +      receive pair for 100BASE-TX.
> +    type: boolean

You should document that happens if the property is not present. Is
the hardware left alone, so the bootloader might of set it to
something other than reset defaults? Is it forced to the highest
common-mode impedance?

Also, is this an on/off setting? Or are there a range of impedance
values which can be set in the hardware? If it is a range, we might
want to be forward thinking and allow a value in ohms.

	Andrew