Subject: Re: [PATCH v3 net-next 1/2] dt-bindings: net: tja11xx: add "nxp,phy-output-refclk" property

From: Rob Herring <[email-masked]>
Date: Mon, 26 Aug 2024 10:49:58 -0500

On Mon, Aug 26, 2024 at 01:26:59PM +0800, Wei Fang wrote:
> Per the RMII specification, the REF_CLK is sourced from MAC to PHY
> or from an external source. But for TJA11xx PHYs, they support to
> output a 50MHz RMII reference clock on REF_CLK pin. Previously the
> "nxp,rmii-refclk-in" was added to indicate that in RMII mode, if
> this property present, REF_CLK is input to the PHY, otherwise it
> is output. This seems inappropriate now. Because according to the
> RMII specification, the REF_CLK is originally input, so there is
> no need to add an additional "nxp,rmii-refclk-in" property to
> declare that REF_CLK is input.
> Unfortunately, because the "nxp,rmii-refclk-in" property has been
> added for a while, and we cannot confirm which DTS use the TJA1100
> and TJA1101 PHYs, changing it to switch polarity will cause an ABI
> break. But fortunately, this property is only valid for TJA1100 and
> TJA1101. For TJA1103/TJA1104/TJA1120/TJA1121 PHYs, this property is
> invalid because they use the nxp-c45-tja11xx driver, which is a
> different driver from TJA1100/TJA1101. Therefore, for PHYs using
> nxp-c45-tja11xx driver, add "nxp,phy-output-refclk" property to
> support outputting RMII reference clock on REF_CLK pin.
> 
> Signed-off-by: Wei Fang <[email-masked]>
> ---
> V2 changes:
> 1. Change the property name from "nxp,reverse-mode" to
> "nxp,phy-output-refclk".
> 2. Simplify the description of the property.
> 3. Modify the subject and commit message.
> V3 changes:
> 1. Keep the "nxp,rmii-refclk-in" property for TJA1100 and TJA1101.
> 2. Rephrase the commit message and subject.
> ---
>  Documentation/devicetree/bindings/net/nxp,tja11xx.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)

This binding is completely broken. I challenge you to make it report any 
errors. Those issues need to be addressed before you add more 
properties.

If you want/need custom properties, then you must have a compatible 
string.

> 
> diff --git a/Documentation/devicetree/bindings/net/nxp,tja11xx.yaml b/Documentation/devicetree/bindings/net/nxp,tja11xx.yaml
> index 85bfa45f5122..f775036a7521 100644
> --- a/Documentation/devicetree/bindings/net/nxp,tja11xx.yaml
> +++ b/Documentation/devicetree/bindings/net/nxp,tja11xx.yaml
> @@ -48,6 +48,12 @@ patternProperties:
>            reference clock output when RMII mode enabled.
>            Only supported on TJA1100 and TJA1101.
>  
> +      nxp,phy-output-refclk:

Why not "nxp,rmii-refclk-out" if this is just the reverse of the 
existing property.

> +        type: boolean
> +        description: |
> +          Enable 50MHz RMII reference clock output on REF_CLK pin. This
> +          property is only applicable to nxp-c45-tja11xx driver.
> +
>      required:
>        - reg
>  
> -- 
> 2.34.1
>