[PATCH 08/16] ARM: bL_platsmp.c: make sure the GIC interface of a dying CPU is disabled

[Nicolas Pitre]

On Mon, 14 Jan 2013, Will Deacon wrote:

> On Mon, Jan 14, 2013 at 04:54:52PM +0000, Nicolas Pitre wrote:
> > On Mon, 14 Jan 2013, Will Deacon wrote:
> > 
> > > On Thu, Jan 10, 2013 at 12:20:43AM +0000, Nicolas Pitre wrote:
> > > > Otherwise there might be some interrupts or IPIs becoming pending and the
> > > > CPU will not enter low power mode when doing a WFI.  The effect of this
> > > > is a CPU that loops back into the kernel, go through the first man
> > > > election, signals itself as alive,  and prevent the cluster from being
> > > > shut down.
> > > > 
> > > > This could benefit from a better solution.
> > > > 
> > > > Signed-off-by: Nicolas Pitre <nico at linaro.org>
> > > > ---
> > > >  arch/arm/common/bL_platsmp.c        | 1 +
> > > >  arch/arm/common/gic.c               | 6 ++++++
> > > >  arch/arm/include/asm/hardware/gic.h | 2 ++
> > > >  3 files changed, 9 insertions(+)
> > > > 
> > > > diff --git a/arch/arm/common/bL_platsmp.c b/arch/arm/common/bL_platsmp.c
> > > > index 0ae44123bf..6a3b251b97 100644
> > > > --- a/arch/arm/common/bL_platsmp.c
> > > > +++ b/arch/arm/common/bL_platsmp.c
> > > > @@ -68,6 +68,7 @@ static void __ref bL_cpu_die(unsigned int cpu)
> > > >  	pcpu = mpidr & 0xff;
> > > >  	pcluster = (mpidr >> 8) & 0xff;
> > > >  	bL_set_entry_vector(pcpu, pcluster, NULL);
> > > > +	gic_cpu_if_down();
> > > 
> > > I'm starting to sound like a stuck record (and not a very tuneful one at
> > > that) but... I think you need a barrier here.
> > 
> > And I'm getting puzzled at the repetition.  ;-)
> 
> Sorry! This case is more interesting though, because you also want to order
> the cpu_if_down GIC write so that it completes before we do the power_off.

In this case I'm leaning toward removing that gic_cpu_if_down() 
entirely.  I'm not convinced it is necessary, and if it is then we 
probably have a bug somewhere else.


Nicolas