FIE assumes the delivered/relative perf registers are fast to read so it goes ahead and hits them quite frequently. On a couple Arm platforms though they end up in PCC regions which require mailbox handshaking with other parts of the platform. This results in a lot of overhead in the cppc_fie task. As such lets runtime disable FIE if we detect it enabled on one of those platforms. Also allow the user to manually enable/disable it via a module parameter. v1->v2: Apply Rafael's review comments. Move the MODULE_PARAM into the ifdef Fix compiler warning when ACPI_CPPC_LIB is disabled. v2->v3: Tristate the module param so FIE can be forced on/off Bump pr_debug to pr_info if FIE is disabled due to PCC regions Switch ACPI_CPPC_CPUFREQ_FIE off by default Jeremy Linton (2): ACPI: CPPC: Disable FIE if registers in PCC regions cpufreq: CPPC: Change FIE default drivers/acpi/cppc_acpi.c | 41 ++++++++++++++++++++++++++++++++++ drivers/cpufreq/Kconfig.arm | 2 +- drivers/cpufreq/cppc_cpufreq.c | 31 +++++++++++++++++++++---- include/acpi/cppc_acpi.h | 5 +++++ 4 files changed, 74 insertions(+), 5 deletions(-) -- 2.37.1
