On platforms supporting Intel Turbo Boost Max Technology 3.0, the
maximum turbo frequencies (turbo ratio) of some cores in a CPU package
may be higher than the other cores in the same package.  In that case,
better performance can be achieved by making the scheduler prefer to run
tasks on the CPUs with higher max turbo frequencies.

On Intel® Broadwell Xeon systems, it is optional to turn on HWP
(Hardware P-States). When HWP is not turned on, the BIOS doesn't
present required CPPC (Collaborative Processor Performance Control)
tables. This table is used to get the per CPU core maximum performance
ratio and inform scheduler (in cpufreq/intel_pstate driver).

On such systems the maximum performance ratio can be read via over
clocking (OC) mailbox interface for each CPU. This interface is not
architectural and can change for every model of processors.

This driver reads maximum performance ratio of each CPU and set up
the scheduler priority metrics. In this way scheduler can prefer CPU
with higher performance to schedule tasks.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>