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With HWP enabled, when the turbo range of performance levels is disabled by the platform firmware, the CPU capacity is given by the "guaranteed performance" field in MSR_HWP_CAPABILITIES which is generally dynamic. When it changes, the kernel receives an HWP notification interrupt handled by notify_hwp_interrupt(). When the "guaranteed performance" value changes in the above configuration, the CPU performance scaling needs to be adjusted so as to use the new CPU capacity in computations, which means that the cpuinfo.max_freq value needs to be updated for that CPU. Accordingly, modify intel_pstate_notify_work() to read MSR_HWP_CAPABILITIES and update cpuinfo.max_freq to reflect the new configuration (this update can be carried out even if the configuration doesn't actually change, because it simply doesn't matter then and it takes less time to update it than to do extra checks to decide whether or not a change has really occurred). Reported-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Tested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> 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.