ACPI: CPPC: Disable FIE if registers in PCC regions

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PCC regions utilize a mailbox to set/retrieve register values used by
the CPPC code. This is fine as long as the operations are
infrequent. With the FIE code enabled though the overhead can range
from 2-11% of system CPU overhead (ex: as measured by top) on Arm
based machines.

So, before enabling FIE assure none of the registers used by
cppc_get_perf_ctrs() are in the PCC region. Finally, add a module
parameter which can override the PCC region detection at boot or
module reload.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

...

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Jeremy Linton 2022-09-12 15:37:22 -05:00 • committed by Rafael J. Wysocki

parent a2a9d18500

commit ae2df912d1

3 changed files with 68 additions and 4 deletions

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42

drivers/acpi/cppc_acpi.c

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25

drivers/cpufreq/cppc_cpufreq.c

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5

include/acpi/cppc_acpi.h

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