arm64: errata: add detection for AMEVCNTR01 incrementing incorrectly
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 and incorrect feedback on CPU frequency. Work around this problem by returning 0 when reading the affected counter in key locations that results in disabling all users of this counter from using it either for frequency invariance or as FFH reference counter. This effect is the same to firmware disabling affected counters. Details on how the two features are affected by this erratum: - 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. Although unlikely, if no alternative method can be found to support frequency i...
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