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Some system BIOS configuration may provide option to disable E-cores. As part of this change, CPUID feature for hybrid (Leaf 7 sub leaf 0, EDX[15] = 0) may not be set. But HWP performance limits will still be using a scaling factor like any other hybrid enabled system. The current check for applying scaling factor will fail when hybrid CPUID feature is not set and the only way to make sure that scaling should be applied by checking CPPC nominal frequency and nominal performance. First, or systems predating Alder Lake, the CPPC nominal frequency and nominal performance are 0, which can be used to distinguish those systems from hybrid systems with disabled E-cores. Second, if the CPPC nominal frequency and nominal performance are defined, which indicates the need to use a special scaling factor, and the nominal performance value multiplied by 100 is not equal to the nominal frequency one, use hybrid scaling factor. This can be done for all HWP systems without additional CPU model check. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> [ rjw: Subject and changelog edits, removal of unneeded parens, comment edits ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.