Re: [PATCH v2 phy 12/16] dt-bindings: phy: lynx-28g: add compatible strings per SerDes and instantiation

Rob Herring (Arm)
2025-09-23T20:37:33Z

On Tue, 23 Sep 2025 22:44:41 +0300, Vladimir Oltean wrote:
> Going by the generic "fsl,lynx-28g" compatible string and expecting all
> SerDes instantiations on all SoCs to use it was a mistake.
>
> They all share the same register map, sure, but the number of protocol
> converters and lanes which are instantiated differs in a way that isn't
> detectable by the programming interface.
>
> Using a separate compatible string per SerDes instantiation is
> sufficient for any device driver to distinguish these features and/or
> any instance-specific quirk. It also reflects how the SoC reference
> manual provides different tables with protocol combinations for each
> SerDes. NXP clearly documents these as not identical, and refers to them
> as such (SerDes 1, 2, etc).
>
> The other sufficient approach would be to list in the device tree all
> protocols supported by each lane. That was attempted in this unmerged
> patch set for the older Lynx 10G family:
> https://lore.kernel.org/linux-phy/20230413160607.4128315-3-sean.anderson@seco.com/
>
> but IMO that approach is more drawn-out and more prone to errors,
> whereas this one is more succinct and obviously correct.
>
> Since this compatible string change breaks forward compatibility of old
> kernels with new device trees (which is OK with the known users), this
> is a good time to fulfill another user request, which is that individual
> SerDes lanes should have had their own OF nodes, so that we can
> customize electrical parameters:
> https://lore.kernel.org/lkml/02270f62-9334-400c-b7b9-7e6a44dbbfc9@solid-run.com/
>
> This request requires #phy-cells = <0>, and because "fsl,lynx-28g"
> requires #phy-cells = <1>, we obviously cannot have both at the same
> time.
>
> Change the expected name of the top-level node to "serdes", and update
> the example too.
>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
> v1->v2:
> - drop the usage of "fsl,lynx-28g" as a fallback compatible
> - mark "fsl,lynx-28g" as deprecated
> - implement Josua's request for per-lane OF nodes for the new compatible
> strings
>
> .../devicetree/bindings/phy/fsl,lynx-28g.yaml | 146 +++++++++++++++++-
> 1 file changed, 140 insertions(+), 6 deletions(-)
>

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:
./Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml:42:18: [error] string value is redundantly quoted with any quotes (quoted-strings)
./Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml:46:18: [error] string value is redundantly quoted with any quotes (quoted-strings)
./Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml:49:18: [error] string value is redundantly quoted with any quotes (quoted-strings)

dtschema/dtc warnings/errors:

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20250923194445.454442-13-vladimir.oltean@nxp.com

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.