On Thu, Jan 25, 2024 at 12:55:12PM +0100, esben@geanix.com wrote:

Krzysztof Kozlowski [off-list ref] writes:

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On 25/01/2024 10:10, esben@geanix.com wrote:

quoted

Conor Dooley [off-list ref] writes:

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On Wed, Jan 24, 2024 at 03:33:06PM +0100, Esben Haabendal wrote:

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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.

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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.

Understood.

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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...

If you look at the current driver, all the devicetree bindings under
rx-queues-config and tx-queues-config are violating the DT binding
rules.
Cleaning up that requires quite some work and I guess will break
backwards compatibility to some extend.

Let bygones be bygones. If something undesirable got in previously,
breaking backwards compatibility there is not justified IMO.