linux-kernel - Re: [PATCH 4/6] regulator: core: Propagate voltage changes to supply regulators

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Date:	Mon, 12 Oct 2015 13:42:59 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Mark Brown <broonie@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
	kernel@...gutronix.de, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/6] regulator: core: Propagate voltage changes to supply
 regulators

Hi Mark,

On Fri, Oct 02, 2015 at 06:32:56PM +0100, Mark Brown wrote:
> On Wed, Sep 30, 2015 at 04:05:44PM +0200, Sascha Hauer wrote:
> 
> > A new min_dropout_uv field is added to struct regulator_desc. Regulators
> > can specify the minimun dropout voltage they need for proper function
> > here. Now when the voltage is changed on a regulator the regulator core
> > makes sure that
> 
> Can we have this interface addition as a separate patch please?  Makes
> it easier to add to other devices.  I could've sworn I'd already done
> that bit but obviously never got the patch mailed out.
> 
> One change I think we need here is only doing the propagation if either
> the device lacks a set_voltage() operation (in which case it's just a
> switch passing through the parent voltage)

Does the lack of a set_voltage() operation automatically mean it's a
switch passing through the parent voltage? What if the regulator is a
fixed regulator and the output can't be controlled because there is only
one voltage?

Currently we bail out int regulator_set_voltage() when we do not have a
set_voltage() or set_voltage_sel() operation. Instead of propagating the
voltage change up I would keep the current behaviour and implement voltage
propagation for switches when we need it. Then we could also introduce a
REGULATOR_IS_SWITCH flag indicating that this is a switch and not a
fixed voltage regulator.

Sascha


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