linux-kernel - Re: [PATCH 1/4] PM / EM: and devices to Energy Model

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Message-ID: <20200120152804.GB164543@google.com>
Date:   Mon, 20 Jan 2020 15:28:04 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     lukasz.luba@....com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
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Subject: Re: [PATCH 1/4] PM / EM: and devices to Energy Model

On Monday 20 Jan 2020 at 15:53:35 (+0100), Dietmar Eggemann wrote:
> Would be really nice if this wouldn't be required. We should really aim
> for 1 framework == 1 set of interfaces.
> 
> What happens if someone calls em_get_pd() on a CPU EM?
> 
> E.g:
> 
>  static struct perf_domain *pd_init(int cpu)
>  {
> -       struct em_perf_domain *obj = em_cpu_get(cpu);
> +       struct device *dev = get_cpu_device(cpu);
> +       struct em_perf_domain *obj = em_pd_get(dev);
>         struct perf_domain *pd;
> 
> Two versions of one functionality will confuse API user from the
> beginning ...

Agreed, this looks a bit confusing. It should be trivial to make
em_dev_get() (or whatever we end up calling it) work for CPUs too,
though. And we could always have a em_cpu_get(int cpu) API that is a
basically a wrapper around em_dev_get() for convenience.

Thanks,
Quentin