On Mon, Sep 12, 2022 at 02:52:26PM +0100, Ionela Voinescu wrote: > commit e89d120c4b720e232cc6a94f0fcbd59c15d41489 upstream. > > The AMU counter AMEVCNTR01 (constant counter) should increment at the same > rate as the system counter. On affected Cortex-A510 cores, AMEVCNTR01 > increments incorrectly giving a significantly higher output value. This > results in inaccurate task scheduler utilization tracking. > > Work around this problem by keeping the reference values of affected > counters to 0. This results in disabling the single user of this > counter: Frequency Invariance Engine (FIE). > This effect is the same to firmware disabling affected counters, in > which case 0 will be returned when reading the disabled counters. > > Therefore, AMU counters will not be used for frequency invariance for > affected CPUs and CPUs in the same cpufreq policy. AMUs can still be used > for frequency invariance for unaffected CPUs in the system. > > The above is achieved through adding a new erratum: ARM64_ERRATUM_2457168. > > Signed-off-by: Ionela Voinescu <ionela.voinescu@xxxxxxx> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Will Deacon <will@xxxxxxxxxx> > Cc: James Morse <james.morse@xxxxxxx> > Link: https://lore.kernel.org/r/20220819103050.24211-1-ionela.voinescu@xxxxxxx > --- > > Hi, > > This is a backport to stable 5.10.142 of the upstream commit > e89d120c4b72 arm64: errata: add detection for AMEVCNTR01 incrementing incorrectly > > This is sent separately as there were conflicts that needed resolving > when applying the mainline patch. Compared to the upstream version this > no longer handles the FFH usecase, as FFH support is not present in 5.10. > Therefore the commit message and Kconfig description are modified to > only describe the effect on FIE caused by this erratum. Both backports now queued up, thanks. greg k-h
