linux-kernel - Re: [PATCH v6 1/4] arm: introduce psci_smp

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Message-ID: <alpine.LFD.2.03.1304181233580.17375@syhkavp.arg>
Date:	Thu, 18 Apr 2013 12:35:57 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"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>,
	"will.deacon@....com" <will.deacon@....com>,
	"arnd@...db.de" <arnd@...db.de>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"marc.zyngier@....com" <marc.zyngier@....com>
Subject: Re: [PATCH v6 1/4] arm: introduce psci_smp_ops

On Thu, 18 Apr 2013, Stefano Stabellini wrote:

> On Thu, 18 Apr 2013, Russell King - ARM Linux wrote:
> > On Fri, Apr 05, 2013 at 02:11:32PM +0100, Stefano Stabellini wrote:
> > > +	psci_init();
> > >  #ifdef CONFIG_SMP
> > >  	if (is_smp()) {
> > > -		smp_set_ops(mdesc->smp);
> > > +		if (mdesc->smp)
> > > +			smp_set_ops(mdesc->smp);
> > > +		else if (psci_smp_available())
> > > +			smp_set_ops(&psci_smp_ops);
> > 
> > So, I have a vague recollection that the ordering of the above got discussed
> > but I can't find it amongst the 21k of messages so far this year.
> > 
> > The above looks weird to me.  Surely this should be:
> > 
> > 		if (psci_smp_available())
> > 			smp_set_ops(&psci_smp_ops);
> > 		else if (mdesc->smp)
> > 			smp_set_ops(mdesc->ops);
> > 
> > This means that if PSCI is available, and provides a set of operations,
> > we override whatever the platform has statically provided.
> > 
> > Remember, we're trying to move away from using "mdesc"s for platform
> > stuff, relying on things like DT and such like.  We really should not
> > be going for mdesc-overriding-newstuff but newstuff-overriding-mdesc.
> 
> That's correct, in fact if you look at the next patch you'll see that it
> changes the order.
> 
> I introduced the mechanism first and changed the priority later - it
> should help bisectability.
> I can fold the two patches into one if you prefer.

Please let's keep the order as we discussed.  Otherwise this is just too 
confusing (Russell's comment is a good example of that).


Nicolas
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