linux-kernel - Re: [PATCH 2/3] dt-bindings: net: snps,dwmac: Add time-based-scheduling property

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Date: Tue, 30 Jan 2024 15:39:26 -0600
From: Rob Herring <robh@...nel.org>
To: Esben Haabendal <esben@...nix.com>
Cc: devicetree@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Giuseppe Cavallaro <peppe.cavallaro@...com>,
	Jose Abreu <joabreu@...opsys.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] dt-bindings: net: snps,dwmac: Add
 time-based-scheduling property

On Wed, Jan 24, 2024 at 03:33:06PM +0100, Esben Haabendal wrote:
> Time Based Scheduling can be enabled per TX queue, if supported by the
> controller.
> 
> Signed-off-by: Esben Haabendal <esben@...nix.com>
> ---
>  Documentation/devicetree/bindings/net/snps,dwmac.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)

This is not v1 which you are aware. Where's the justification or do I 
need to ask the same questions again? Here's the last discussion[1].

I'm still not clear on why this is needed. Seems like the combination of 
TBS and TSO capabilities provides enough information. If TSO is enabled 
for a queue, then don't enable TBS.

This binding is already such a mess of properties, I'm inclined to say 
"what's one more", but it's death by 1000 cuts. Part of the problem is 
this binding is for not 1 IP block, but something that's evolved over 
at least 15 years. 

The question on configuration properties really comes down to who would 
configure things and when. If it's one time for the life of given h/w, 
then DT makes sense. If every user wants/needs to tweak the setting, 
then definitely shouldn't be in DT. Somewhere in the middle? Judgement 
call.

> diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> index 5c2769dc689a..301e9150ecc3 100644
> --- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> +++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> @@ -399,6 +399,12 @@ properties:
>              type: boolean
>              description: TX checksum offload is unsupported by the TX queue.
>  
> +          snps,time-based-scheduling:
> +            type: boolean
> +            description:
> +              Time Based Scheduling will be enabled for TX queue.
> +              This is typically not supported for TX queue 0.

Make the property name clear it is an enable, not a capability.

> +

[1] https://lore.kernel.org/all/20230929051758.21492-1-rohan.g.thomas@intel.com/