linux-kernel - Re: Voltage setting on chained regulators, how?

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Message-ID: <20150929150017.GR30445@sirena.org.uk>
Date:	Tue, 29 Sep 2015 16:00:17 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Sascha Hauer <s.hauer@...gutronix.de>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Liam Girdwood <lgirdwood@...il.com>, kernel@...gutronix.de,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: Voltage setting on chained regulators, how?

On Tue, Sep 29, 2015 at 10:00:44AM +0200, Sascha Hauer wrote:
> On Fri, Sep 25, 2015 at 09:47:26AM -0700, Mark Brown wrote:

> > I suspect you always want the LDO in there to clean the supply up, it's
> > just a more serious issue when more power is being drawn.

> I just had a look at the i.MX6 datasheets and saw that while it's
> possible to put the LDOs in bypass mode the expected lifetime of the SoC
> decreases without the LDOs. So it seems better to let them enabled and
> just make the voltage drop as small as possible.

Yeah, that sounds pretty standard.  It would be really good to get
support for minimising the voltage drop over the LDO, there are going to
be quite a few systems which could get a power consumption benefit from
dynamically tuning the voltages of DCDCs like this.

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