linux-kernel - Re: [linux-sunxi] [PATCH] ARM: dts: sunxi: Raise minimum CPU voltage for sun7i-a20 to a level all boards can supply

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Date:	Mon, 3 Aug 2015 11:28:39 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Julian Calaby <julian.calaby@...il.com>
Cc:	Chen-Yu Tsai <wens@...e.org>, public_timo.s@...entcreek.de,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	devicetree <devicetree@...r.kernel.org>,
	"Mailing List, Arm" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [PATCH] ARM: dts: sunxi: Raise minimum CPU voltage
 for sun7i-a20 to a level all boards can supply

On Mon, Aug 03, 2015 at 02:22:13PM +1000, Julian Calaby wrote:
> >> 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?
> >
> > You could try. Though I really don't see much to gain here.
> 
> From what I recall, lower frequency = less power usage, though my
> experience is from x86 laptops, not ARM SoCs and I'm sure I'm missing
> a lot of details. This is the sort of thing that requires thorough
> testing on a dev board.

Not on *a* dev board. On virtually all the A20 SoCs ever produced. If
you have a setting that works better for *your* SoC, fine, patch your
DT, but that's not going to be a default if it's outside of the SoC
operating range.

Maxime

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

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