Agilex™ 5 ES Device Errata and User Guidelines

ID 825514
Date 12/09/2024
Public
Document Table of Contents

3.5.6. 2666383: PMU event 0x2 (TLB Miss) triggers incorrectly in TCU

Description

PMU event 0x2 is expected to fire at most once per transaction when a TLB lookup result requires further memory access to produce a translation result. Affected versions only issue the PMU event when there is a complete miss in the Walk Cache on initial lookup. The event can trigger 0, 1 or 2 times for each time a transaction passes through the TCU and may trigger too many or too few times.

Conditions

This affects all Walk Cache hits that return a partial translation result when the PMU system is programmed to count the event.

Impact

A PMU counter counting transactions that require memory accesses to complete the translation may undercount or overcount them. This event is therefore not usable in practice.

Workaround

Depending on your translation regime, it may be possible to use the "S1L3 WC miss" event (0x87), or a different appropriate stage and level-specific miss event instead.

Category

Category C