linux-kernel - Re: [PATCH v5 1/8] Documentation: arm: define DT cpu capacity-dmips-mhz bindings

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Date:	Wed, 15 Jun 2016 15:24:32 +0100
From:	Juri Lelli <juri.lelli@....com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Sudeep Holla <sudeep.holla@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Mark Brown <broonie@...nel.org>,
	Sai Charan Gurrappadi <sgurrappadi@...dia.com>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Olof Johansson <olof@...om.net>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	Paul Walmsley <paul@...an.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Chen-Yu Tsai <wens@...e.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Subject: Re: [PATCH v5 1/8] Documentation: arm: define DT cpu
 capacity-dmips-mhz bindings

On 15/06/16 14:51, Vincent Guittot wrote:
> On 15 June 2016 at 12:17, Juri Lelli <juri.lelli@....com> wrote:

[...]

> > +==========================================
> > +ARM CPUs capacity bindings
> > +==========================================
> > +
> > +==========================================
> > +1 - Introduction
> > +==========================================
> > +
> > +ARM systems may be configured to have cpus with different power/performance
> > +characteristics within the same chip. In this case, additional information
> > +has to be made available to the kernel (the scheduler in particular) for
> 
> not sure that it's worth mentioning the scheduler in particular here
> 

OK. I can remove that bit.

> > +it to be aware of such differences and take decisions accordingly.
> > +

[...]

> > +==========================================
> > +3 - capacity-dmips-mhz
> > +==========================================
> > +
> > +capacity-dmips-mhz is an optional cpu node [1] property: u32 value
> > +representing CPU capacity expressed in normalized DMIPS/MHz. At boot time, the
> > +maximum frequency available to the cpu is then used to calculate the capacity
> > +value internally used by the kernel.
> > +
> > +capacity-dmips-mhz property is all-or-nothing: if it is specified for a cpu
> > +node, it has to be specified for every other cpu nodes, or the system will
> > +fall back to the default capacity value for every CPU. If cpufreq is not
> > +available, final capacities are calculated by directly using capacity-dmips-
> > +mhz values (normalized w.r.t. the highest value found while parsing the DT).
> 
> looks good to me
> 

Great! Thanks for reviewing this.

Best,

- Juri