linux-kernel - Re: [PATCH 1/1] cpufreq: cpufreq-cpu0: use the max voltage instead of voltage-tolerance

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Message-ID: <20131107022639.GB5994@S2101-09.ap.freescale.net>
Date:	Thu, 7 Nov 2013 10:26:41 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	Rongjun Ying <Rongjun.Ying@....com>
CC:	Viresh Kumar <viresh.kumar@...aro.org>, rjying <rjying@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Barry Song <Barry.Song@....com>
Subject: Re: [PATCH 1/1] cpufreq: cpufreq-cpu0: use the max voltage instead
 of voltage-tolerance

On Thu, Nov 07, 2013 at 01:55:21AM +0000, Rongjun Ying wrote:
> > For given board, what voltages could be provided is known.  So you can
> > just define OPP table in <board>.dts and specify the voltage as the
> > value that the regulator IC can supply, e.g. 1.200V in above example.
> > 
> > This is not nice, as OPP table is CPU/SoC specific and should be
> > ideally defined in <soc>.dtsi.  But still it's a way out for you to use
> > cpufreq-cpu0 driver as it is.
> > 
> > In any case, you can not just change voltage-tolerance to voltage-max
> > with no care about the existing users.
> > 
> > Shawn
> > 
> I don't think so. The voltage/freq pairs are attribute of the CPU.
> Any boards can choose regulator IC base the cost and other reasons.
> If the opp table defined in <board>.dts, we can set exact voltage/freq pairs,
> and not need use the voltage-tolerance to set tolerance.

If you read my comment above, you should see that I agree OPP is
CPU/SoC specific and should be defined in <soc>.dtsi.  But property
operating-points can reasonably be overwritten by particular <board>.dts
for some reason like some voltages cannot be supplied on that board.

Again, this is just a way for you to use generic cpufreq-cpu0 driver as
it is, but not necessarily the best one.

Shawn

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