arm: Use the Self-Synchronized counter registers
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Authored by andrew on Aug 8 2025, 12:21 PM.

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rG0aef3b56caad: arm: Use the Self-Synchronized counter registers
rG0efa0fe26b9d: arm: Use the Self-Synchronized counter registers

Summary

When FEAT_ECV is implemented on arm64 a Self-Synchronized view of the
counter registers are available. These don't need an isb before reading
the count as they are not able to be speculatively executed.

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rG FreeBSD src repository

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Buildable 66100
Build 62983: arc lint + arc unit

Event Timeline

andrew created this revision.Aug 8 2025, 12:21 PM

Herald added a subscriber: imp. · View Herald TranscriptAug 8 2025, 12:21 PM

andrew requested review of this revision.Aug 8 2025, 12:21 PM

Harbormaster completed remote builds in B66100: Diff 160047.Aug 8 2025, 12:21 PM

andrew added a parent revision: D51819: arm64: Add more counter/timer registers.Aug 8 2025, 12:21 PM

andrew added a child revision: D51821: arm64/vmm: Use FEAT_ECV_POFF to support a timer.

This revision was not accepted when it landed; it landed in state Needs Review.Sep 23 2025, 5:10 PM

Closed by commit rG0efa0fe26b9d: arm: Use the Self-Synchronized counter registers (authored by andrew). · Explain Why

This revision was automatically updated to reflect the committed changes.

andrew added a commit: rG0efa0fe26b9d: arm: Use the Self-Synchronized counter registers.

andrew added a commit: rG0aef3b56caad: arm: Use the Self-Synchronized counter registers.Jan 14 2026, 12:55 AM

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sys/

arm/

generic_timer.c

25 lines

Diff 160047

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sys/arm/arm/generic_timer.c

arm: Use the Self-Synchronized counter registersClosedPublicActions