linux-kernel - Re: [RFC PATCH] regulator: core: allow consumers to request to closes step voltage

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Message-ID: <20130619223828.GK1403@sirena.org.uk>
Date:	Wed, 19 Jun 2013 23:38:28 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Nishanth Menon <nm@...com>
Cc:	Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org
Subject: Re: [RFC PATCH] regulator: core: allow consumers to request to
 closes step voltage

On Wed, Jun 19, 2013 at 02:17:54PM -0500, Nishanth Menon wrote:

> Account for step size accuracy when exact voltage requests are send for
> step based regulators.

If the consumer can tolerate a different voltage why not just request
the range that can be tolerated?  Your problem here is specifying an
exact voltage.

> The specific example I faced was using cpufreq-cpu0 driver with voltages
> for OPPs for MPU rail and attempting the common definitions against voltages
> that are non-exact multiples of stepsize of PMIC.

> The alternative would be implement custom set_voltage (as againsta simpler
> set_voltage_sel and using linear map/list functions) for the regulator which
> will account for the same.

> Yet another alternative might be to introduce yet another custom function similar
> to regulator_set_voltage_tol which accounts for this. something like:
> regulator_set_voltage_floor(regulator, voltage, tol) or something to that effect.

Or as I keep telling you guys the consumer can just do that directly
using the existing API; the whole point in specifying the voltage as a
range is to allow the consumer to cope with arbatrary regulators by
giving a range of voltages that it can accept.

The API is deliberately very conservative in these matters since there
is a danger of physical damage if things really go wrong in some
applications, it makes sure that both the drivers and the system
integration are involved.

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