linux-kernel - Re: [PATCH 2/4] soc: Mediatek: Add SCPSYS power domain driver

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Date:	Mon, 13 Apr 2015 12:55:57 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Kevin Hilman <khilman@...nel.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Matthias Brugger <matthias.bgg@...il.com>,
	devicetree@...r.kernel.org, linux-mediatek@...ts.infradead.org,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH 2/4] soc: Mediatek: Add SCPSYS power domain driver

On Tue, Mar 31, 2015 at 09:27:53AM -0700, Kevin Hilman wrote:
> Hi Sascha,
> 
> Sascha Hauer <s.hauer@...gutronix.de> writes:
> 
> > This adds a power domain driver for the Mediatek SCPSYS unit.
> >
> > The System Control Processor System (SCPSYS) has several power
> > management related tasks in the system. The tasks include thermal
> > measurement, dynamic voltage frequency scaling (DVFS), interrupt
> > filter and lowlevel sleep control. The System Power Manager (SPM)
> > inside the SCPSYS is for the MTCMOS power domain control.
> >
> > For now this driver only adds power domain support, the more
> > advanced features are not yet supported. The driver implements
> > the generic PM domain device tree bindings, the first user will
> > most likely be the Mediatek AFE audio driver.
> >
> > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> 
> Sorry for the lag, was travelling last week at ELC and not keeping up
> with reviews.
> 
> This version looks pretty good to me, but had one minor
> comment/question...
> 
> [...]
> 
> > +#define NUM_DOMAINS	ARRAY_SIZE(scp_domain_data)
> > +
> > +struct scp;
> > +
> > +struct scp_domain {
> > +	struct generic_pm_domain pmd;
> > +	struct scp_domain_data *data;
> > +	struct scp *scp;
> > +};
> > +
> > +struct scp {
> > +	struct scp_domain domains[NUM_DOMAINS];
> > +	struct generic_pm_domain *pmd[NUM_DOMAINS];
> 
> Why is this genpd pointer needed?  It's just a pointer to the
> .domains.pmd[i] anyways, and IMO makes the code a bit hard to follow.

The driver itself does not need the genpd pointer, but
of_genpd_add_provider_onecell() expects an array of pointers to struct
generic_pm_domain.

I can allocate the array of pointers separately and remove the pmd field
from struct scp to make this a bit more clearer.

Sascha

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