netdev - Re: [PATCH] dt-bindings: net: renesas,ethertsn: Add bindings for Ethernet TSN

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Date: Tue, 21 Nov 2023 13:20:54 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Cc: Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 devicetree@...r.kernel.org, netdev@...r.kernel.org,
 linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: net: renesas,ethertsn: Add bindings for
 Ethernet TSN

On 21/11/2023 13:10, Niklas Söderlund wrote:
>>> +
>>> +  phy-handle:
>>> +    $ref: /schemas/types.yaml#/definitions/phandle
>>> +    description:
>>> +      Specifies a reference to a node representing a PHY device.
>>
>> You miss top-level $ref to ethernet controller
> 
> Sorry I don't fully understand what you are asking here, there are a few 
> things about bindings I still need to learn. Looking at other bindings 
> some have a
> 
> maintainers:
>   ..
> 
> allOf:
>   - $ref: ethernet-controller.yaml#

This one.

> 
> properties:
>  ..
> 
> Is it this all ollOff node I'm missing?
> 
>>
>>> +
>>> +  renesas,rx-internal-delay:
>>> +    type: boolean
>>> +    description:
>>> +      Enable internal Rx clock delay, typically 1.8ns.
>>
>> Why this is bool, not delay in ns?
> 
> The TSN is only capable of enabling or disable internal delays, not set 
> how long the delay is. The documentation states that the delay depends 
> on the electronic characteristics of the particular board, but states 
> that they typically are 1.8ns for Rx and 2.0ns for Tx.

I don't understand that part. If you cannot configure the internal
delay, how could it depend on the board characteristics?

> 
> I looked at the generic properties {rx,tx}-internal-delay-ps but they 
> are of int type. So I opted for a vendor specific bool property. Do you 
> think a better route is to use the generic property and force the value 
> to be either 0 or the typical delay?
> 
>> Why this is property of a board (not SoC)?
> 
> I'm sorry I don't understand this question.

Why setting internal delay is specific to a board, not to a SoC? Why
each board would need to configure it? On which parts of hardware on the
board does this depend?


Best regards,
Krzysztof