linux-kernel - RE: [PATCH] ARM: b.L: fix unmet dependency for CPU

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Message-id: <001401cfffd1$ae9df930$0bd9eb90$@samsung.com>
Date:	Fri, 14 Nov 2014 11:40:06 +0530
From:	Pankaj Dubey <pankaj.dubey@...sung.com>
To:	'Nicolas Pitre' <nicolas.pitre@...aro.org>,
	'Russell King - ARM Linux' <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	james.hogan@...tec.com, ccross@...roid.com
Subject: RE: [PATCH] ARM: b.L: fix unmet dependency for CPU_PM

+CC: Colin Cross, James Hogan

On Thursday, November 13, 2014 11:30 PM, Nicolas Pitre wrote:
> To: Russell King - ARM Linux
> Cc: Pankaj Dubey; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH] ARM: b.L: fix unmet dependency for CPU_PM
> 
> On Thu, 13 Nov 2014, Russell King - ARM Linux wrote:
> 
> > On Thu, Nov 13, 2014 at 12:44:22PM -0500, Nicolas Pitre wrote:
> > > On Thu, 13 Nov 2014, Pankaj Dubey wrote:
> > >
> > > > If BL_SWITCHER is enabled but SUSPEND and CPU_IDLE is not enabled
> > > > we are getting following config warning.
> > > >
> > > > warning: (BL_SWITCHER) selects CPU_PM which has unmet direct
> > > > dependencies (SUSPEND || CPU_IDLE)
> > > >
> > > > So BL_SWITCHER should enable CPU_PM only if either of SUSPEND or
> > > > CPU_IDLE is selected.
> > > >
> > > > Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> > > > ---
> > > >  arch/arm/Kconfig |    2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index
> > > > 9d580d0..fe3d969 100644
> > > > --- a/arch/arm/Kconfig
> > > > +++ b/arch/arm/Kconfig
> > > > @@ -1417,7 +1417,7 @@ config BL_SWITCHER
> > > >  	bool "big.LITTLE switcher support"
> > > >  	depends on BIG_LITTLE && MCPM && HOTPLUG_CPU
> > > >  	select ARM_CPU_SUSPEND
> > > > -	select CPU_PM
> > > > +	select CPU_PM if (SUSPEND || CPU_IDLE)
> > >
> > > NAK.  You just broke the code by doing this. CPU_PM is a requirement
> > > here.  The dependencies for CPU_PM is lacking.
> >

OK, got it. Even though compilation worked, but as you mentioned by doing
this way
bL_switcher functionality may broke.

> > Is there any real technical reason that CPU_PM depends on SUSPEND ||
> > CPU_IDLE ?  If not, those dependencies should be killed.
> 
> Those dependencies look artificial to me.
> 

For me also it looks like these dependencies are artificial.
As far as I can see CONFIG_CPU_PM compiles following two files 
1: kernel/cpu_pm.c - I can't see any dependency of SUSPEND or CPU_IDLE in
this file.
2: arch/mips/kernel/pm.c: A quick look does not show any dependency of
SUSPEND or
   CPU_IDLE here too.

So for me it looks like it is OK to kill these dependencies of CPU_PM. 
Still safer side I am CCing this to author of these files for confirmation.

Thanks,
Pankaj Dubey
> 
> Nicolas

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