linux-kernel - Re: [PATCH v2 2/2] [RFC] CPUFreq: Add support for cpu-perf-dependencies

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Date:   Mon, 12 Oct 2020 17:02:46 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     Rob Herring <robh@...nel.org>,
        Nicola Mazzucato <nicola.mazzucato@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ionela Voinescu <ionela.voinescu@....com>,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        vireshk@...nel.org, daniel.lezcano@...aro.org, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, chris.redpath@....com,
        morten.rasmussen@....com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] [RFC] CPUFreq: Add support for
 cpu-perf-dependencies

On Mon, Oct 12, 2020 at 11:22:57AM +0100, Lukasz Luba wrote:
[...]

> 
> True, the SCMI clock does not support discovery of clock tree:
> (from 4.6.1 Clock management protocol background)
> 'The protocol does not cover discovery of the clock tree, which must be
> described through firmware tables instead.' [1]
>

By firmware, spec refers to DT or ACPI, just to be clear.

> In this situation, would it make sense, instead of this binding from
> patch 1/2, create a binding for internal firmware/scmi node?
>

Why ? I prefer to solve this in a generic way and make it not scmi
specific issue. If OPP idea Viresh suggested can be made to work, that
would be good.

> Something like:
> 
> firmware {
> 	scmi {
> 	...		
> 		scmi-perf-dep {
> 			compatible = "arm,scmi-perf-dependencies";
> 			cpu-perf-dep0 {
> 				cpu-perf-affinity = <&CPU0>, <&CPU1>;
> 			};
> 			cpu-perf-dep1 {
> 				cpu-perf-affinity = <&CPU3>, <&CPU4>;
> 			};
> 			cpu-perf-dep2 {
> 				cpu-perf-affinity = <&CPU7>;
> 			};
> 		};
> 	};
> };
> 
> The code which is going to parse the binding would be inside the
> scmi perf protocol code and used via API by scmi-cpufreq.c.
>

Not completely against it, just need to understand how is this solved
or will be solved for any DT(non SCMI) and why it can be generic.

-- 
Regards,
Sudeep