linux-kernel - RE: [PATCH 1/2] regulator: support operating mode in the device tree structure

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Message-ID: <A874F61F95741C4A9BA573A70FE3998F82E5C9C8@DQHE06.ent.ti.com>
Date:	Tue, 7 May 2013 23:46:12 +0000
From:	"Kim, Milo" <Milo.Kim@...com>
To:	Mark Brown <broonie@...nel.org>
CC:	Liam Girdwood <lgirdwood@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] regulator: support operating mode in the device
 tree structure

> -----Original Message-----
> From: Mark Brown [mailto:broonie@...nel.org]
> Sent: Wednesday, May 08, 2013 1:05 AM
> To: Kim, Milo
> Cc: Liam Girdwood; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 1/2] regulator: support operating mode in the
> device tree structure
> 
> On Tue, May 07, 2013 at 01:09:14PM +0000, Kim, Milo wrote:
> > For better power efficiency, regulator subsystem provides operating
> mode.
> > (fast, normal, idle and standby)
> > The operating mode is selective by a regulator consumer.
> >
> > With this patch, regulator operating mode can be set in the DT
> structure.
> > If any operating mode is configured, then 'valid_ops_mask' should be
> set with
> > REGULATOR_CHANGE_MODE.
> 
> It's not clear to me that these modes are a useful thing to be exposing
> in device tree - they've always been rather arbatrary and are becoming
> less and less relevant as regulator hardware improves in its ability to
> adapt to load.  I think for fixed modes that don't vary dynamically at
> runtime the best thing is just to make the modes custom so they map
> onto
> the device datasheets clearly.  That seems to be most of the usage
> anyway.

I agree the operating mode depends on the device.

It's my intention to guarantee same operations in the DT as the regulator
constraints in the platform side.
In case a regulator has specific 'valid_modes_mask', the operating mode is 
unable to be set with the device tree.
For some regulator drivers such as LP8720/5 and LP8788, this patch would be
useful because there is no difference between configuration in the platform side
 and the device tree.

Thanks,
Milo

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