The base_frequency display in cpufreq sysfs for intel_pstate gets the guaranteed ratio by reading CPPC guaranteed performance register as a first preference before falling back to x86 MSR for Hardware P-state Capabilities. The current code in cppc_acpi.c assumed that "guaranteed performance register" can be an integer field, which is invalid as per ACPI spec. So this change explicitly check for INTEGER values for invalid BIOS/firmware and ignore. Also guaranteed performance register field is optional and when not present, nominal performance can be used as the guaranteed performance. But spec calls that this is true only in non-autonomous mode. So no change is made in cppc_acpi.c to make nominal as guaranteed in this case to avoid dependency on autonomous and non-autonomous mode. Instead a change is added to intel_pstate driver, which is specific to x86 to make nominal as guaranteed when guaranteed performance field is absent or has invalid value. Also we are working to clarify this non-autonomous mode requirement through ACPI standard body. v2: Changes done as suggested by Rafael. Srinivas Pandruvada (2): ACPI / CPPC: Fix processing for guaranteed performance cpufreq: intel_pstate: Also use cppc nominal_perf for base_frequency drivers/acpi/cppc_acpi.c | 9 +++++++-- drivers/cpufreq/intel_pstate.c | 5 ++++- 2 files changed, 11 insertions(+), 3 deletions(-) -- 2.17.2
