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From ACPI spec below 3 modes for CPPC can be defined:
1. Non autonomous: OS scaling governor specifies operating frequency/
performance level through `Desired Performance` register and platform
follows that.
2. Guided autonomous: OS scaling governor specifies min and max
frequencies/ performance levels through `Minimum Performance` and
`Maximum Performance` register, and platform can autonomously select an
operating frequency in this range.
3. Fully autonomous: OS only hints (via EPP) to platform for the required
energy performance preference for the workload and platform autonomously
scales the frequency.
Currently (1) is supported by amd_pstate as passive mode, and (3) is
implemented by EPP support. This change is to support (2).
In guided autonomous mode the min_perf is based on the input from the
scaling governor. For example, in case of schedutil this value depends
on the current utilization. And max_perf is set to max capacity.
To activate guided auto mode ``amd_pstate=guided`` command line
parameter has to be passed in the kernel.
Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Wyes Karny <wyes.karny@amd.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.