linux-kernel - Re: [PATCH net-next v1 2/3] dt-bindings: net: micrel: Add keep-preamble-before-sfd

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Message-Id: <176553538562.3334907.2349485324753514759.robh@kernel.org>
Date: Fri, 12 Dec 2025 04:29:47 -0600
From: "Rob Herring (Arm)" <robh@...nel.org>
To: Stefan Eichenberger <eichest@...il.com>
Cc: kuba@...nel.org, krzk+dt@...nel.org, linux-kernel@...r.kernel.org, 
 netdev@...r.kernel.org, davem@...emloft.net, geert+renesas@...der.be, 
 francesco.dolcini@...adex.com, conor+dt@...nel.org, 
 rafael.beims@...adex.com, ben.dooks@...ethink.co.uk, 
 Stefan Eichenberger <stefan.eichenberger@...adex.com>, hkallweit1@...il.com, 
 edumazet@...gle.com, devicetree@...r.kernel.org, andrew+netdev@...n.ch, 
 pabeni@...hat.com, linux@...linux.org.uk
Subject: Re: [PATCH net-next v1 2/3] dt-bindings: net: micrel: Add
 keep-preamble-before-sfd


On Fri, 12 Dec 2025 09:46:17 +0100, Stefan Eichenberger wrote:
> From: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> 
> Add a property to activate a Micrel PHY feature that keeps the preamble
> enabled before the SFD (Start Frame Delimiter) is transmitted.
> 
> This allows to workaround broken Ethernet controllers as found on the
> NXP i.MX8MP. Specifically, errata ERR050694 that states:
> ENET_QOS: MAC incorrectly discards the received packets when Preamble
> Byte does not precede SFD or SMD.
> 
> The bit which disables this feature is not documented in the datasheet
> from Micrel, but has been found by NXP and Micrel following this
> discussion:
> https://community.nxp.com/t5/i-MX-Processors/iMX8MP-eqos-not-working-for-10base-t/m-p/2151032
> 
> It has been tested on Verdin iMX8MP from Toradex by forcing the PHY to
> 10MBit. Withouth this property set, no packets are received. With this
> property set, reception works fine.
> 
> Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> ---
>  Documentation/devicetree/bindings/net/micrel.yaml | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 

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

yamllint warnings/errors:
./Documentation/devicetree/bindings/net/micrel.yaml:517:1: [warning] too many blank lines (2 > 1) (empty-lines)

dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/net/renesas,ether.example.dtb: ethernet-phy@1 (ethernet-phy-id0022.1537): compatible: ['ethernet-phy-id0022.1537', 'ethernet-phy-ieee802.3-c22'] is too long
	from schema $id: http://devicetree.org/schemas/net/micrel.yaml

doc reference errors (make refcheckdocs):

See https://patchwork.kernel.org/project/devicetree/patch/20251212084657.29239-3-eichest@gmail.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.