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Date: Mon, 31 Mar 2008 12:48:14 -0500
From: Josh Boyer <jwboyer@linux.vnet.ibm.com>
To: jyoung5@us.ibm.com
Subject: Re: [kvm-ppc-devel] [PATCH] Add idle power save for ppc 4xx
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Cc: kvm-ppc-devel@lists.sourceforge.net, linuxppc-dev@ozlabs.org,
	Hollis Blanchard <hollisb@us.ibm.com>
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On Mon, 31 Mar 2008 11:52:02 -0500
Jerone Young <jyoung5@us.ibm.com> wrote:

> > void ppc4xx_idle(void)
> > 
> > > +{
> > > +	unsigned long msr_save;
> > > +
> > > +	/* set wait state MSR */
> > > +	local_irq_enable();
> > > +	msr_save = mfmsr();
> > > +	mtmsr(msr_save|MSR_WE);
> > 
> > Why don't you |MSR_WE|MSR_EE at the same time?
> 
> You technically can do this. But the question is do all 4xx cpus use
> MSR_EE to enable interrupts? I can assume they do (from what I know),

They do for enabling external interrupts of normal priority.  MSR_CE
might also be used/needed if someone has the watchdog enabled or has an
external device with the UIC pin mapped as a CE.

josh