linux-kernel - Re: [PATCH 00/14] cpufreq: cpu0: Extend support beyond CPU0, V2

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Message-ID: <2399813.Puj1SZWhCh@vostro.rjw.lan>
Date:	Fri, 18 Jul 2014 03:02:49 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Nishanth Menon <nm@...com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Simon Horman <horms@...ge.net.au>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas P Abraham <thomas.ab@...sung.com>,
	Rob Herring <rob.herring@...aro.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Arvind Chauhan <arvind.chauhan@....com>,
	Sachin Kamat <spk.linux@...il.com>,
	Michal Simek <michal.simek@...inx.com>
Subject: Re: [PATCH 00/14] cpufreq: cpu0: Extend support beyond CPU0, V2

On Thursday, July 17, 2014 01:11:45 PM Viresh Kumar wrote:
> On 17 July 2014 13:05, Thomas Petazzoni
> <thomas.petazzoni@...e-electrons.com> wrote:
> > Could you summarize what is the issue with the binding?
> >
> > At least for the case where we have one clock per CPU, the DT binding
> > is really dead simple: each CPU node can carry a "clocks" property, and
> > a "clock-latency" property. I really don't see why a long discussion is
> > needed to agree on such a binding.
> >
> > Now, if the DT binding problem is related to those cases where you have
> > siblings, i.e one clock controlling *some* of the CPUs, but not all
> > CPUs or just one CPU, then maybe we could leave this aside for now,
> 
> Yeah, we are stuck on that for now.
> 
> > only support the following cases:
> >
> >  * One clock for all CPUs
> >  * One clock for each CPU
> 
> Yeah, so I also proposed this yesterday that we stick to only these
> two implementations for now. And was looking at how would the
> cpufreq-generic driver come to know about this.
> 
> So, one way out now is to see if "clocks" property is defined in
> multiple cpu nodes, if yes don't compare them and consider separate
> clocks for each cpu. We don't have to try matching that to any other
> node, as that's a very bad idea. Mike was already very upset with that :)
> 
> @Stephen/Rafael: Does that sound any better? Ofcourse the final thing
> is to get bindings to figure out relations between CPUs..

Before I apply anything in this area, I need a clear statement from the ARM
people as a group on what the approach is going to be.

Rafael

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