linux-kernel - Re: [PATCH v4 2/3] PM / EM: Expose perf domain struct

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Date:   Wed, 15 May 2019 11:56:30 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     edubezval@...il.com, rui.zhang@...el.com, javi.merino@...nel.org,
        viresh.kumar@...aro.org, amit.kachhap@...il.com, rjw@...ysocki.net,
        will.deacon@....com, catalin.marinas@....com,
        dietmar.eggemann@....com, ionela.voinescu@....com,
        mka@...omium.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 2/3] PM / EM: Expose perf domain struct

On 15/05/2019 11:17, Quentin Perret wrote:
> Hi Daniel,
> 
> On Wednesday 15 May 2019 at 11:06:18 (+0200), Daniel Lezcano wrote:
>> On 15/05/2019 10:23, Quentin Perret wrote:
>>> In the current state, the perf_domain struct is fully defined only when
>>> CONFIG_ENERGY_MODEL=y. Since we need to write code that compiles both
>>> with or without that option in the thermal framework, make sure to
>>> actually define the struct regardless of the config option. That allows
>>> to avoid using stubbed accessor functions all the time in code paths
>>> that use the EM.
>>>
>>> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
>>> Signed-off-by: Quentin Perret <quentin.perret@....com>
>>
>> This patch implies the cpu cooling device can be set without the energy
>> model.
>>
>> Isn't it possible to make a strong dependency for the cpu cooling device
>> on the energy model option, add the energy model as default on arm arch
>> and drop this patch?
> 
> Right, that should work too.
> 
>> After all, the cpu cooling is using the em framework.
> 
> The reason I did it that way is simply to keep things flexible. If you
> don't compile in THERMAL_GOV_POWER_ALLOCATOR, you will never use the EM
> for CPU thermal. So I thought it would be good to not mandate compiling
> in ENERGY_MODEL in this case -- that should save a bit of space.
> 
> But TBH I don't have a strong opinion on this one, so if everybody
> agrees it's fine to just make CPU_THERMAL depend on ENERGY_MODEL, I'm
> happy to drop this patch and fix patch 3/3. That would indeed simplify
> things a bit.

Ok in this case it will be better to drop the 2/3 and add a small series
doing for the cpu_cooling.c

#ifdef CONFIG_THERMAL_GOV_POWER_ALLOCATOR

/* structure freq */

/* power2state */

/* state2power*/

/* getrequestedpower */

/* All functions needed for the above */

#endif

static struct thermal_cooling_device_ops cpufreq_cooling_ops = {
        .get_max_state          = cpufreq_get_max_state,
        .get_cur_state          = cpufreq_get_cur_state,
        .set_cur_state          = cpufreq_set_cur_state,
#ifdef CONFIG_THERMAL_GOV_POWER_ALLOCATOR
        .get_requested_power    = cpufreq_get_requested_power,
        .state2power            = cpufreq_state2power,
        .power2state            = cpufreq_power2state,
#endif
};

So you don't have to care about ENERGY_MODEL to be set as
THERMAL_GOV_POWER_ALLOCATOR depends on it.

I think the result for cpu_cooling.c will be even more cleaner with the
em change.




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