ACPI / CPPC: add sysfs support to compute delivered performance
The CPPC tables contain entries for per CPU feedback counters which allows us to compute the delivered performance over a given interval of time. The math for delivered performance per the CPPCv5.0+ spec is: reference perf * delta(delivered perf ctr)/delta(ref perf ctr) Maintaining deltas of the counters in the kernel is messy, as it depends on when the reads are triggered. (e.g. via the cpufreq ->get() interface). Also the ->get() interace only returns one value, so cant return raw values. So instead, leave it to userspace to keep track of raw values and do its math for CPUs it cares about. delivered and reference perf counters are exposed via the same sysfs file to avoid the potential "skid", if these values are read individually from userspace. Signed-off-by:Prashanth Prakash <pprakash@codeaurora.org> Signed-off-by:
Ashwin Chaugule <ashwin.chaugule@linaro.org> Signed-off-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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