[PATCH 1/2] ARM: perf: reset counters on all CPUs during initialisation

Will Deacon will.deacon at arm.com
Wed Mar 23 09:39:22 EDT 2011

Hi Jean,

> On Wed, Mar 16, 2011 at 4:38 PM, Will Deacon <will.deacon at arm.com> wrote:
> > ARMv7 dictates that the interrupt-enable and count-enable registers for
> > each PMU counter are UNKNOWN following core reset.
> Great! Is this development driven by actual issues or by precaution?
> >
> > This patch adds an arch_initcall to the ARMv7 perf events backend which
> > disables the counters on each CPU prior to setting the Enable bit in the
> > PMCR.
> Also the function rename is a good thing.
> >
> > Cc: Jean Pihet <jean.pihet at newoldbits.com>
> > Signed-off-by: Will Deacon <will.deacon at arm.com>
> Acked-by: Jean Pihet <j-pihet at ti.com>

I don't think this patch is safe for combined v6/v7 kernels because the
arch_initcall will try to poke the v7 PMU regardless of whether or not
it exists. I'll try and rework something and send another version to the

I've removed it from the patch system but left the isb patch there
because that is fine as it is.

Stay tuned...


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