linux-kernel - Re: FW: [PATCH v2] mmc: sdhci: apply voltage range check only for non-fixed regulators

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Message-ID: <20121114084105.GG7407@opensource.wolfsonmicro.com>
Date:	Wed, 14 Nov 2012 17:41:07 +0900
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Kevin Liu <keyuan.liu@...il.com>
Cc:	m.szyprowski@...sung.com, Chris Ball <cjb@...top.org>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	kyungmin.park@...sung.com, lrg@...com,
	Philip Rakity <prakity@...dia.com>
Subject: Re: FW: [PATCH v2] mmc: sdhci: apply voltage range check only for
 non-fixed regulators

On Wed, Nov 14, 2012 at 04:36:28PM +0800, Kevin Liu wrote:
> 2012/11/14 Mark Brown <broonie@...nsource.wolfsonmicro.com>:

> > Should this be regulator_set_voltage_tol()?  Otherwise it'd be good to
> > explain where the numbers come from.

> In SD physical layer spec 3.01 chapter 6.6.1, the threshold level for
> voltage range is defined as below:
> Vdd(min) = 2.7V while Vdd(max) = 3.6V.
> The card should work within the voltage range.

> If you are afraid the voltage value is too aggressive, maybe we can
> use regulator_set_voltage_tol() to set a smaller range.
> But which range should be reasonable?

The above makes total sense - thanks!  I just wasn't aware that the
range was specified in this fashion in the spec.  Might be worth a
comment in the code if you need to respin.

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