linux-kernel - Re: [PATCH v8 2/2] ARM: Enable selection of SMP operations at boot time

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Message-ID: <alpine.DEB.2.02.1304251123410.4180@kaball.uk.xensource.com>
Date:	Thu, 25 Apr 2013 11:25:01 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Will Deacon <will.deacon@....com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"olof@...om.net" <olof@...om.net>, Jon Medhurst <tixy@...aro.org>
Subject: Re: [PATCH v8 2/2] ARM: Enable selection of SMP operations at boot
 time

On Thu, 25 Apr 2013, Will Deacon wrote:
> On Wed, Apr 24, 2013 at 07:40:19PM +0100, Stefano Stabellini wrote:
> > From: Jon Medhurst <tixy@...aro.org>
> > 
> > Add a new 'smp_init' hook to machine_desc so platforms can specify a
> > function to be used to setup smp ops instead of having a statically
> > defined value.  The hook must return true when smp_ops are initialized.
> > If false the static mdesc->smp_ops will be used by default.
> > 
> > Signed-off-by: Jon Medhurst <tixy@...aro.org>
> > Signed-off-by: Nicolas Pitre <nicolas.pitre@...aro.org>
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > Reviewed-by: Santosh Shilimkar <santosh.shilimkar@...com>
> > ---
> >  arch/arm/include/asm/mach/arch.h |    4 ++++
> >  arch/arm/kernel/setup.c          |   10 ++++++----
> >  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> [...]
> 
> >  	if (is_smp()) {
> > -		if (psci_smp_available())
> > -			smp_set_ops(&psci_smp_ops);
> > -		else if (mdesc->smp)
> > -			smp_set_ops(mdesc->smp);
> > +		if (!mdesc->smp_init || !mdesc->smp_init()) {
> 
> Minor nit, but this feels backwards to me. We usually return 0 on success,
> yet we're saying here that if mdesc->smp_init() returns 0, then we go and
> override the smp ops.

I am OK with changing the interface to return an int instead of a bool,
but given that Nicolas is the main user of smp_init at the moment, I'll
wait for his opinion.
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