linux-kernel - Re: [PATCH 4/7] soc/tegra: pmc: Add interface to set voltage of IO rails

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Message-ID: <20160415080027.GB3217@sirena.org.uk>
Date:	Fri, 15 Apr 2016 09:00:27 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Laxman Dewangan <ldewangan@...dia.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Jon Hunter <jonathanh@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 4/7] soc/tegra: pmc: Add interface to set voltage of IO
 rails

On Fri, Apr 15, 2016 at 09:54:34AM +0200, Linus Walleij wrote:
> On Tue, Apr 12, 2016 at 4:56 PM, Laxman Dewangan <ldewangan@...dia.com> wrote:

> > NVIDIA Tegra210 supports some of the IO interface which can operate
> > at 1.8V or 3.3V I/O rail voltage levels. SW needs to configure
> > Tegra PMC register to set different voltage level of IO interface based
> > on IO rail voltage from power supply i.e. power regulators.

> Nobody seems to mention the elephant in the room: why is this
> not using the regulator subsystem and instead using custom
> code under drivers/soc? We have worried before about drivers/soc
> becoming a dumping ground akin to drivers/misc

The above changelog sounds like a regulator consumer not a regulator -
based on what I'm reading there it's a driver that looks at the voltage
being supplied to the device and sets some configuration in the device
based on that voltage.  This isn't that unusual for analogue circuits
but it's definitely not something that's actually doing voltage
regulation.

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