linux-kernel - Re: [PATCH v2 03/17] PM: EM: Refactor em_pd_get_efficient

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Message-ID: <4e16fb56-7628-8b2f-182b-170a85168cb8@arm.com>
Date:   Mon, 3 Jul 2023 17:22:48 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     rui.zhang@...el.com, amit.kucheria@...durent.com,
        amit.kachhap@...il.com, daniel.lezcano@...aro.org,
        viresh.kumar@...aro.org, len.brown@...el.com, pavel@....cz,
        Pierre.Gondois@....com, ionela.voinescu@....com,
        rostedt@...dmis.org, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        rafael@...nel.org
Subject: Re: [PATCH v2 03/17] PM: EM: Refactor em_pd_get_efficient_state() to
 be more flexible



On 5/30/23 12:06, Dietmar Eggemann wrote:
> On 12/05/2023 11:57, Lukasz Luba wrote:
>> Prepare em_pd_get_efficient_state() for the upcoming changes and
>> make it possible to re-use. Return an index for the best performance
> 
> Don't get the `possible to re-use`? Did you mean `possible to be
> re-used`? But then `re-used` for what?

The function will no longer get a pointer to 'struct em_perf_domain'
but instead to 'struct em_perf_state'. It would also require to
get the number of states from 'pd->nr_perf_states'.

This is preparation for handling 2 tables:
modifiable (a) and default (b).

Then it also returns and ID not the pointer to state.
It all makes it more generic and ready for those 2 tables.

> 
>> state. The function arguments that are introduced should allow to
>> work on different performance state arrays. The caller of
>> em_pd_get_efficient_state() should be able to use the index either
>> on the default or the modifiable EM table.
> 
> This describes the WHAT but not the WHY.

I will add that description as 'why' in the header. I wanted to
avoid mentioning in the patch description something which
is coming in the next patch.