linux-kernel - Re: [RFC PATCH v3 03/10] PM: Introduce an Energy Model management framework

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Message-ID: <20180608103113.GB418@e108498-lin.cambridge.arm.com>
Date:   Fri, 8 Jun 2018 11:31:14 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>, peterz@...radead.org,
        rjw@...ysocki.net, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        mingo@...hat.com, morten.rasmussen@....com, chris.redpath@....com,
        patrick.bellasi@....com, valentin.schneider@....com,
        vincent.guittot@...aro.org, thara.gopinath@...aro.org,
        viresh.kumar@...aro.org, tkjos@...gle.com, joelaf@...gle.com,
        smuckle@...gle.com, adharmap@...cinc.com, skannan@...cinc.com,
        pkondeti@...eaurora.org, edubezval@...il.com,
        srinivas.pandruvada@...ux.intel.com, currojerez@...eup.net,
        javi.merino@...nel.org
Subject: Re: [RFC PATCH v3 03/10] PM: Introduce an Energy Model management
 framework

On Friday 08 Jun 2018 at 11:36:13 (+0200), Juri Lelli wrote:
> On 08/06/18 09:25, Quentin Perret wrote:
> > Hi Dietmar,
> > 
> > On Thursday 07 Jun 2018 at 17:55:32 (+0200), Dietmar Eggemann wrote:
> 
> [...]
> 
> > > IMHO, part of the problem why this might be harder to understand is the fact
> > > that the patches show the use of the 2. init call
> > > 'em_rescale_cpu_capacity()' but not the 1. one 'em_register_freq_domain()'.
> > > I guess that Quentin wanted to keep the set as small as possible.
> > 
> > Yes, this is confusing. I'm now starting to think that patch 10/10 should
> > probably not be part of this patch-set, especially if I don't provide
> > the patches registering the freq domains from the CPUFreq drivers. And
> > it's the only "Arm-specific" patch in this arch-independent patch-set.
> > 
> > So I think I'll drop patch 10/10 for v4 ... That part should be
> > discussed separately, with the rest of the Arm-specific changes.
> 
> Mmm, I would actually vote to at least have one example showing how and
> where the em_register_freq_domain() is going to be used. I had to look
> at the repo you referenced since I think it's quite fundamental piece to
> understand the design, IMHO.

Hmmm I see your point. OK, having an example will help. I'll keep patch
10/10 and add an other one tweaking cpufreq-dt to give an example. But
I'll mark the two as OPTIONAL. I really hope we can reach an agreement
on the core design ideas before discussing too much the details on the
driver side.

There are several valid places where em_register_freq_domain() can be
called. But the exact way of doing so will be platform-dependent, and
driver-dependent, so let's agree on what we want to know from the
drivers first :-)

Thanks,
Quentin