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

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Date:	Thu, 7 Nov 2013 03:32:09 +0000
From:	Rongjun Ying <Rongjun.Ying@....com>
To:	Shawn Guo <shawn.guo@...aro.org>
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



> -----Original Message-----
> From: Shawn Guo [mailto:shawn.guo@...aro.org]
> Sent: Thursday, November 07, 2013 10:27 AM
> To: Rongjun Ying
> Cc: Viresh Kumar; rjying; Rafael J. Wysocki; cpufreq@...r.kernel.org;
> linux-pm@...r.kernel.org; Linux Kernel Mailing List; Barry Song
> 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
> 

I think my patch is better.
All soc have a max work voltage. If regulator IC can't supply min voltage, 
It can supply max voltage to soc.
As my patch, not need overwrite OPP in <board>.dts.
As your comment above, almost all board need overwrite OPP, unless the regulator 
IC can supply all voltage ranges of SoC need.

Thanks
-RongJun Ying
> 
> 
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