Re: [PATCH v2 0/2] CPPC: reduce FFH feedback-counter sampling skew on arm64

[Will Deacon]

On Wed, 08 Jul 2026 16:28:16 +0800, Pengjie Zhang wrote:
> The legacy CPPC feedback-counter path reads the delivered and reference
> performance counters separately.
> 
> On arm64 systems using AMU-backed CPPC FFH counters, each FFH read is
> served through a cross-CPU counter read helper. Reading the counters
> separately therefore widens the sampling window between them and can
> skew the delivered/reference ratio used by cpuinfo_cur_freq. Under heavy
> load, the skew is observable as transient values that may exceed the
> platform maximum, as discussed in [1] and [2].
> 
> [...]

Applied to arm64 (for-next/acpi), thanks!

[1/2] ACPI: CPPC: add paired FFH feedback-counter read hook
      https://git.kernel.org/arm64/c/9aa7df520523
[2/2] arm64: topology: read CPPC FFH feedback counters in one operation
      https://git.kernel.org/arm64/c/42971d5329d9

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
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