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Diffstat (limited to 'Documentation/admin-guide/pm/amd-pstate.rst')
| -rw-r--r-- | Documentation/admin-guide/pm/amd-pstate.rst | 78 |
1 files changed, 74 insertions, 4 deletions
diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index 5376d53faaa8..d143e72cf93e 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -230,8 +230,8 @@ with :c:macro:`MSR_AMD_CPPC_ENABLE` or ``cppc_set_enable``, it will respond to the request from AMD P-States. -User Space Interface in ``sysfs`` -================================== +User Space Interface in ``sysfs`` - Per-policy control +====================================================== ``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to control its functionality at the system level. They are located in the @@ -262,6 +262,25 @@ lowest non-linear performance in `AMD CPPC Performance Capability <perf_cap_>`_.) This attribute is read-only. +``energy_performance_available_preferences`` + +A list of all the supported EPP preferences that could be used for +``energy_performance_preference`` on this system. +These profiles represent different hints that are provided +to the low-level firmware about the user's desired energy vs efficiency +tradeoff. ``default`` represents the epp value is set by platform +firmware. This attribute is read-only. + +``energy_performance_preference`` + +The current energy performance preference can be read from this attribute. +and user can change current preference according to energy or performance needs +Please get all support profiles list from +``energy_performance_available_preferences`` attribute, all the profiles are +integer values defined between 0 to 255 when EPP feature is enabled by platform +firmware, if EPP feature is disabled, driver will ignore the written value +This attribute is read-write. + Other performance and frequency values can be read back from ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`. @@ -280,8 +299,30 @@ module which supports the new AMD P-States mechanism on most of the future AMD platforms. The AMD P-States mechanism is the more performance and energy efficiency frequency management method on AMD processors. -Kernel Module Options for ``amd-pstate`` -========================================= + +AMD Pstate Driver Operation Modes +================================= + +``amd_pstate`` CPPC has two operation modes: CPPC Autonomous(active) mode and +CPPC non-autonomous(passive) mode. +active mode and passive mode can be chosen by different kernel parameters. +When in Autonomous mode, CPPC ignores requests done in the Desired Performance +Target register and takes into account only the values set to the Minimum requested +performance, Maximum requested performance, and Energy Performance Preference +registers. When Autonomous is disabled, it only considers the Desired Performance Target. + +Active Mode +------------ + +``amd_pstate=active`` + +This is the low-level firmware control mode which is implemented by ``amd_pstate_epp`` +driver with ``amd_pstate=active`` passed to the kernel in the command line. +In this mode, ``amd_pstate_epp`` driver provides a hint to the hardware if software +wants to bias toward performance (0x0) or energy efficiency (0xff) to the CPPC firmware. +then CPPC power algorithm will calculate the runtime workload and adjust the realtime +cores frequency according to the power supply and thermal, core voltage and some other +hardware conditions. Passive Mode ------------ @@ -298,6 +339,35 @@ processor must provide at least nominal performance requested and go higher if c operating conditions allow. +User Space Interface in ``sysfs`` - General +=========================================== + +Global Attributes +----------------- + +``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to +control its functionality at the system level. They are located in the +``/sys/devices/system/cpu/amd-pstate/`` directory and affect all CPUs. + +``status`` + Operation mode of the driver: "active", "passive" or "disable". + + "active" + The driver is functional and in the ``active mode`` + + "passive" + The driver is functional and in the ``passive mode`` + + "disable" + The driver is unregistered and not functional now. + + This attribute can be written to in order to change the driver's + operation mode or to unregister it. The string written to it must be + one of the possible values of it and, if successful, writing one of + these values to the sysfs file will cause the driver to switch over + to the operation mode represented by that string - or to be + unregistered in the "disable" case. + ``cpupower`` tool support for ``amd-pstate`` =============================================== |