linux-kernel - Re: [PATCH 3/3 RESEND] mmc: sdhci: check voltage range only on regulators aware of voltage value

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Date:	Thu, 14 Feb 2013 09:05:43 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Guennadi Liakhovetski <g.liakhovetski@....de>,
	linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Liam Girdwood <lrg@...com>, Chris Ball <cjb@...top.org>,
	Kevin Liu <keyuan.liu@...il.com>
Subject: Re: [PATCH 3/3 RESEND] mmc: sdhci: check voltage range only on
 regulators aware of voltage value

On 2/13/2013 12:35 PM, Mark Brown wrote:
> On Wed, Feb 13, 2013 at 08:45:56AM +0100, Guennadi Liakhovetski wrote:
> > On Wed, 13 Feb 2013, Marek Szyprowski wrote:
>
> > > BTW, mmc_regulator_get_ocrmask() won't work with continuous range regulators.
>
> > This seems like a problem, that has to be fixed...
>
> Indeed, what's the issue?

There are probably 2 issues:

1. mmc_regulator_get_ocrmask() works only with regulators which support
regulator_count_voltages() and regulator_list_voltage(). Recently 
support for
continuous regulators have been merged. Such regulators doesn't provide
regulator_list_voltage() method, but are able to change/set voltage to the
given value. I agree that they are not very common, so right now we can
probably ignore them until the first board, which uses them arrives.

2. The second issue might be related to the testing of precise voltage 
values
in the ocr mask, not the whole allowed ranges. Such issues in sdhci.c 
driver
has been recently fixed by commit cec2e216f72c6b5ccdadb60aadbe99821d744503
("mmc: sdhci: Use regulator min/max voltage range according to spec"), but I
don't know MMC core code to judge if ocr mask is used for exact voltage
checking or only for checking the voltage ranges. However someone with good
mmc subsystem knowledge should check it.

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center

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