linux-kernel - Re: [RFC PATCH 1/4] regulator: Introduce OMAP regulator to control PMIC over VC/VP

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Message-ID: <20130613145803.GA32324@kahuna>
Date:	Thu, 13 Jun 2013 09:58:03 -0500
From:	Nishanth Menon <nm@...com>
To:	Mark Brown <broonie@...nel.org>
CC:	Paul Walmsley <paul@...an.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Tony Lindgren <tony@...mide.com>,
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-doc@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	Grygorii Strashko <grygorii.strashko@...com>
Subject: Re: [RFC PATCH 1/4] regulator: Introduce OMAP regulator to control
 PMIC over VC/VP

On 15:47-20130613, Mark Brown wrote:
> On Thu, Jun 13, 2013 at 08:39:50AM -0500, Nishanth Menon wrote:
> 
> > I am having a bit of a difficulty trying to understand your concern
> > here.
> 
> Your device tree for this stuff appears to mostly consist of repeating
> the description of the PMIC that we already have - this really doesn't
> seem like a great result.
> 
> > Problem statement:
> 
> > OMAP has this weird custom h/w where one programs the voltage and that
> > voltage is send over i2c - this is not same as Tegra's lookup table
> > array which automatically sends out entries, in OMAP, software has to trigger
> > the voltage transition
> 
> The basic idea that's important here is that you need to figure out how
> to tell the hardware what to write - how those writes get triggered is a
> separate problem.
> 
> > If your concern was describing PMIC parameters in dts, I can easily move
> > them inside the omap_pmic driver and provide required compatible flags.
> > If, on the other hand, the entire approach followed is flawed, I'd like to
> > understand the rationale for the same.
> 
> That's the biggest problem I saw so far but to be honest I've not
> drilled down too much into the specifics.  From my point of view the
> main thing is how this fits into the frameworks and so on, having the
> register information in the DT was an alarm flag that suggested the
> overall approach was a concern.
OK. would you be ok with an generic omap_pmic driver if the PMIC
specific data set is moved into OF compatible data?
I am proposing moving the following into OF match data.
ti,i2c-slave-address
ti,i2c-voltage-register
ti,i2c-command-register
ti,slew-rate-microvolt
ti,step-size-micro-volts
ti,voltage-selector-set-bits
ti,voltage-selector-mask
ti,voltage-selector-offset
ti,non-zero-voltage-selector

The only thing I propose to retain is board specific variations - e.g.
gpios, boot voltage and standard regulator min,max overrides if any.

I can also do voltage selector based operations while at it.

-- 
Regards,
Nishanth Menon
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