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From: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
Subject: Re: [PATCH] ARM: dts: sunxi: Raise minimum CPU voltage
 for sun7i-a20 to a level all boards can supply
Date: Mon, 3 Aug 2015 11:16:24 +0200
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To: Julian Calaby <julian.calaby-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: public_timo.s-fWgRPtSzPNU3WX+qO2AYSQ@public.gmane.org, Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>, Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>, Ian Campbell <ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org>, Kumar Gala <galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, devicetree <devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "Mailing List, Arm" <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-sunxi <linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org>, Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>
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On Mon, Aug 03, 2015 at 09:35:51AM +1000, Julian Calaby wrote:
> Hi Timo,
> 
> On Mon, Aug 3, 2015 at 5:23 AM, Timo Sigurdsson
> <public_timo.s-fWgRPtSzPNU3WX+qO2AYSQ@public.gmane.org> wrote:
> > sun7i-a20.dtsi contains an cpufreq operating point at 0.9 volts. Most A20 boards
> > (or all?), however, do not allow the voltage to go below 1.0V. Thus, raise the
> > voltage for the lowest operating point to 1.0V so all boards can actually use
> > it.
> 
> Surely it wouldn't be added here if some could supply 0.9v.
> 
> Is the code that uses this smart enough to sensibly switch between two
> operating points with the same frequency and different voltages? If
> so, maybe just add a 144MHz @ 1.0v operating point?

And how would it choose between the two exactly ? Switch to the 144MHz
@ 0.9V and see if it works ? If it doesn't you might have screwed your
system already, and might not be able to recover from it at all.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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