FIE assumes the delivered/relative perf registers are fast to read so it goes ahead and hits them quite frequently. On a couple of 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. Lastly, allow the user to override this decision 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 v3->v4: No functional change, resend due to email addr issues v4->v5: Minor whitespace, comment wording, if/case conversion Drop the ACPI_CPPC_CPUFREQ_FIE disable config change added in v3 Jeremy Linton (1): ACPI: CPPC: Disable FIE if registers in PCC regions drivers/acpi/cppc_acpi.c | 42 ++++++++++++++++++++++++++++++++++ drivers/cpufreq/cppc_cpufreq.c | 25 ++++++++++++++++---- include/acpi/cppc_acpi.h | 5 ++++ 3 files changed, 68 insertions(+), 4 deletions(-) -- 2.37.1
