Messages in this thread | | | Date | Fri, 8 Mar 2013 07:11:28 +0100 (CET) | From | Guennadi Liakhovetski <> | Subject | Re: [PATCH V2] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue |
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Hi Viresh
On Fri, 8 Mar 2013, Viresh Kumar wrote:
> On 8 March 2013 05:56, Guennadi Liakhovetski <g.liakhovetski@gmx.de> wrote: > > I like generic drivers :) > > Me too :) > > > cpufreq-cpu0 is yet another such generic > > (cpufreq) driver. Now, comparing the functionality of the two: > > Great!! > > > we see, that this driver "only" switches CPU clock frequencies. Whereas > > the cpufreq-cpu0 driver also manipulates a regulator (if available) > > directly. I understand, power-saving is also an important consideration > > for big.LITTLE systems. So, I presume, you plan to implement voltage > > switching in cpufreq notifiers? > > So the platform on which we are currently testing these is ARM TC2 Soc > and this switching is done by the firmware instead. And so didn't went > for regulator hookups initially.. Obviously in future regulator hookups would > find some space in this driver but not required for now. > > > Now, my question is: is this (notifier) > > actually the preferred method and the cpufreq-cpu0 driver is doing it > > "wrongly?" > > What notifiers are you talking about? I believe using the regulator framework > is the right way of doing this. And that would be part of this code later on.
Also in your driver you're doing
cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE); ... cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
So, theoretically you could install such notifiers to adjust CPU voltages (using regulators too). But adding regulator calls directly to the driver would make it consistent with cpufreq-cpu0.c, so, if this doesn't violate any concepts, I think, it would be good to add those when suitable systems appear.
Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/
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