linux-kernel - Re: [PATCH v2 3/4] cpufreq: mediatek: add Mediatek cpufreq driver

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Message-ID: <CAKohpon8kXzfeKUUwrRhuei0cY9iVbMHfBjDwXW=M2SAYHdtYQ@mail.gmail.com>
Date:	Wed, 18 Mar 2015 12:29:43 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Pi-Cheng Chen <pi-cheng.chen@...aro.org>
Cc:	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Chen Fan <fan.chen@...iatek.com>,
	Howard Chen <ibanezchen@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	linux-mediatek@...ts.infradead.org,
	Kumar Gala <galak@...eaurora.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	"Joe.C" <yingjoe.chen@...iatek.com>,
	Eddie Huang <eddie.huang@...iatek.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/4] cpufreq: mediatek: add Mediatek cpufreq driver

On 12 March 2015 at 16:45, Pi-Cheng Chen <pi-cheng.chen@...aro.org> wrote:
> The voltages of the two regulators need to be always under a limitation:
> 100mV < Vsram - Vproc < 200mV
> For now, I just calculate the OPPs of Vsram from OPPs of Vproc.
>
> Another thing I should mention, if the voltage difference of two adjacent
> OPPs is greater than 100mV, we need to set the regulator to some
> voltages which are not in OPP table considering the limitation above.
> I think that will make it more difficult to model such flow in a generic
> framework.

Actually the problem is that OPP tables are insufficient for such cases,
and we are adding work-arounds to fix that. Though it will get fixed
with the new bindings we are adding.

I am confused on what we should be doing here. Even if you write
your own driver, you will be abusing DT with incorrect information.

Even if you go around adding a new driver, I would like you to fallback
to cpufreq-dt ones the new OPP bindings are in place.
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