linux-kernel - Re: [PATCH 3/3] mmc: sdhci: apply voltage range check only for non-fixed regulators

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Date:	Wed, 14 Nov 2012 10:10:43 +0900
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Chris Ball <cjb@...top.org>
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Liam Girdwood <lrg@...com>
Subject: Re: [PATCH 3/3] mmc: sdhci: apply voltage range check only for
 non-fixed regulators

On Tue, Nov 13, 2012 at 07:45:07AM -0500, Chris Ball wrote:
> On Tue, Nov 13 2012, Marek Szyprowski wrote:
> > Fixed regulators cannot change their voltage, so disable all voltage range
> > checking for them, otherwise the driver fails to operate with fixed
> > regulators.

> > Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>

> Perhaps it's a good idea to mention that the regulator API is changing
> (being fixed) at the same time, and that's why this patch is necessary.

This should be totally unrelated to any externally visible change in the
regulator API, if anything I would expect fixes in the API to *improve*
the ability of clients to work with fixed voltage regulators.  What's
missing here is some explanation as to what the problem is and how it's
being fixed.

As I understand it this should really be a workaround for hardware which
runs cards at out of spec voltages; we have a fixed voltage regulator
which claims to not support any of the voltages that are in spec (due to
this being what the hardware does) so if we try to use the voltage
management stuff in the MMC API it gets upset.  As a workaround if we
can't change the voltage we just ignore the voltage aspects of the API.

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