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Date: Thu, 18 Jun 2009 09:22:18 +1000
From: Paul Mackerras <paulus@samba.org>
To: Kumar Gala <galak@kernel.crashing.org>
Subject: Re: [PATCH 1/6] perf_counter: powerpc: Enable use of software
	counters on 32-bit powerpc
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Cc: Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
	linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
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Kumar Gala writes:

> On Jun 17, 2009, at 6:50 AM, Paul Mackerras wrote:

> > +config PPC_HAVE_PMU_SUPPORT
> > +       bool
> 
> what does this mean?

At the moment it means that arch/powerpc/kernel/perf_counters.c works
for at least some processors in the selected processor family.

> > +
> > +config PPC_PERF_CTRS
> > +       def_bool y
> > +       depends on PERF_COUNTERS && PPC_HAVE_PMU_SUPPORT
> > +       help
> > +         This enables the powerpc-specific perf_counter back-end.
> 
> Can we distinguish between the two different architected perf counters  
> programming models to start with.  Maybe something like:
> 
> PPC_BOOK3S_PERF_CTRS and PPC_BOOK3E_PERF_CTRS (or  
> PPC_SERVER_PERF_CTRS / PPC_EMB_PERF_CTRS)

We can do that once we have code to support the Freescale embedded PMU
and we know how much of arch/powerpc/kernel/perf_counters.c is or
isn't useful there.  We don't have to get to the final state in one
patch.  I'd rather put this patch in as-is and then see a patch series
that adds the Freescale embedded PMU support and makes whatever
Kconfig changes are necessary later.

Paul.