Re: [PATCH 3/4] perf: arm_pmu: Add workaround for FUJITSU-MONAKA Erratum E#030002

[Will Deacon]

On Fri, Oct 02, 2026 at 07:26:51PM +0900, Tomohiro Misono wrote:
> FUJITSU-MONAKA Erratum E#030002 affects FUJITSU-MONAKA CPU.
> 
> On affected FUJITSU-MONAKA CPUs, after a PMU event counter is
> stopped at a value just before overflow, an overflow might still
> be incorrectly detected, resulting interrupt storm in some case.
> 
> Work around the erratum by avoiding programming PMU event counters
> with values within five counts of overflow.

What's the user-visible behaviour of this erratum? It's not entirely clear
to me why we need to do anything at all.

Will