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

[Krzysztof Kozlowski]

On 25/01/2024 10:10, esben@xxxxxxxxxx wrote:
> Conor Dooley <conor@xxxxxxxxxx> writes:
> 
>> 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.
>>
>> If time based scheduling is not supported by the controller, then the
>> property should not be present! The presence of a property like this
>> should mean that the feature is supported, using it is up to the
>> operating system.
>>
>> That said, why is this a property that should be in DT?
> 
> It is added to the tx-queues-config object of snps,dwmac bindings. This
> entire object is about configuration of the ethernet controller, which
> is also what the purpose of the snps,time-based-scheduling.
> So yes, it is not specifically about describing what the hardware is
> capable of, but how the hardware is configured. It is a continuation of
> the current driver design.
> 
>> If support is per controller is it not sufficient to use the
>> compatible to determine if this is supported?
> 
> Are you suggesting to include the mapping from all supported compatible
> controllers to which TX queues supports TBS in the driver code?  What
> would the benefit of that compared to describing it explicitly in the
> binding?

The benefit is complying with DT bindings rules, saying that bindings
describe hardware pieces, not drivers.

> And for the purpose of the above question, I am talking about it as if
> the binding was describing the hardware capability and not the
> configuration.

"if"? You wrote it is for driver design...

Best regards,
Krzysztof