diff options
Diffstat (limited to 'Documentation/admin-guide/pm/intel_idle.rst')
| -rw-r--r-- | Documentation/admin-guide/pm/intel_idle.rst | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/Documentation/admin-guide/pm/intel_idle.rst b/Documentation/admin-guide/pm/intel_idle.rst index afbf778035f8..89309e1b0e48 100644 --- a/Documentation/admin-guide/pm/intel_idle.rst +++ b/Documentation/admin-guide/pm/intel_idle.rst @@ -60,6 +60,9 @@ of the system. The former are always used if the processor model at hand is recognized by ``intel_idle`` and the latter are used if that is required for the given processor model (which is the case for all server processor models recognized by ``intel_idle``) or if the processor model is not recognized. +[There is a module parameter that can be used to make the driver use the ACPI +tables with any processor model recognized by it; see +`below <intel-idle-parameters_>`_.] If the ACPI tables are going to be used for building the list of available idle states, ``intel_idle`` first looks for a ``_CST`` object under one of the ACPI @@ -165,7 +168,7 @@ and ``idle=nomwait``. If any of them is present in the kernel command line, the ``MWAIT`` instruction is not allowed to be used, so the initialization of ``intel_idle`` will fail. -Apart from that there are two module parameters recognized by ``intel_idle`` +Apart from that there are four module parameters recognized by ``intel_idle`` itself that can be set via the kernel command line (they cannot be updated via sysfs, so that is the only way to change their values). @@ -186,9 +189,28 @@ QoS) feature can be used to prevent ``CPUIdle`` from touching those idle states even if they have been enumerated (see :ref:`cpu-pm-qos` in :doc:`cpuidle`). Setting ``max_cstate`` to 0 causes the ``intel_idle`` initialization to fail. -The ``noacpi`` module parameter (which is recognized by ``intel_idle`` if the -kernel has been configured with ACPI support), can be set to make the driver -ignore the system's ACPI tables entirely (it is unset by default). +The ``no_acpi`` and ``use_acpi`` module parameters (recognized by ``intel_idle`` +if the kernel has been configured with ACPI support) can be set to make the +driver ignore the system's ACPI tables entirely or use them for all of the +recognized processor models, respectively (they both are unset by default and +``use_acpi`` has no effect if ``no_acpi`` is set). + +The value of the ``states_off`` module parameter (0 by default) represents a +list of idle states to be disabled by default in the form of a bitmask. + +Namely, the positions of the bits that are set in the ``states_off`` value are +the indices of idle states to be disabled by default (as reflected by the names +of the corresponding idle state directories in ``sysfs``, :file:`state0`, +:file:`state1` ... :file:`state<i>` ..., where ``<i>`` is the index of the given +idle state; see :ref:`idle-states-representation` in :doc:`cpuidle`). + +For example, if ``states_off`` is equal to 3, the driver will disable idle +states 0 and 1 by default, and if it is equal to 8, idle state 3 will be +disabled by default and so on (bit positions beyond the maximum idle state index +are ignored). + +The idle states disabled this way can be enabled (on a per-CPU basis) from user +space via ``sysfs``. .. _intel-idle-core-and-package-idle-states: |