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Date: Thu, 25 Jan 2024 17:14:55 +0000
From: Conor Dooley <conor@kernel.org>
To: esben@geanix.com
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
	devicetree@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Jose Abreu <joabreu@synopsys.com>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] dt-bindings: net: snps,dwmac: Add
 time-based-scheduling property
Message-ID: <20240125-pebble-reproach-f550d00a2abb@spud>
References: <b365dc6f756a3fad4dfaa2675c98f4078aba8a55.1706105494.git.esben@geanix.com>
 <30ce8f45b8752c603acc861ebb2f18d74d2f8a07.1706105494.git.esben@geanix.com>
 <20240124-reptilian-icing-a95b20f123be@spud>
 <87bk99hj7q.fsf@geanix.com>
 <3adf7908-be27-4125-ae5b-6f2eb6100304@linaro.org>
 <877cjxhbkv.fsf@geanix.com>
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On Thu, Jan 25, 2024 at 12:55:12PM +0100, esben@geanix.com wrote:
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
>=20
> > On 25/01/2024 10:10, esben@geanix.com wrote:
> >> Conor Dooley <conor@kernel.org> writes:
> >>=20
> >>> 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 t=
he
> >>>> 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?
> >>=20
> >> 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.
> >>=20
> >>> If support is per controller is it not sufficient to use the
> >>> compatible to determine if this is supported?
> >>=20
> >> 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.
>=20
> Understood.
>=20
> >> 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...
>=20
> 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.

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