Commit af3a1b6a authored by Artem Bityutskiy's avatar Artem Bityutskiy Committed by Rafael J. Wysocki
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Documentation: admin-guide: pm: Document intel_idle C1 demotion 



Document the intel_idle driver sysfs file for enabling/disabling C1
demotion.

Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://patch.msgid.link/20250317135541.1471754-3-dedekind1@gmail.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 6138f345

Documentation/admin-guide/pm/intel_idle.rst

+21 −0
Original line number Diff line number Diff line
@@ -38,6 +38,27 @@ instruction at all. 
only way to pass early-configuration-time parameters to it is via the kernel

command line.



Sysfs Interface

===============



The ``intel_idle`` driver exposes the following ``sysfs`` attributes in

``/sys/devices/system/cpu/cpuidle/``:



``intel_c1_demotion``

	Enable or disable C1 demotion for all CPUs in the system. This file is

	only exposed on platforms that support the C1 demotion feature and where

	it was tested. Value 0 means that C1 demotion is disabled, value 1 means

	that it is enabled. Write 0 or 1 to disable or enable C1 demotion for

	all CPUs.



	The C1 demotion feature involves the platform firmware demoting deep

	C-state requests from the OS (e.g., C6 requests) to C1. The idea is that

	firmware monitors CPU wake-up rate, and if it is higher than a

	platform-specific threshold, the firmware demotes deep C-state requests

	to C1. For example, Linux requests C6, but firmware noticed too many

	wake-ups per second, and it keeps the CPU in C1. When the CPU stays in

	C1 long enough, the platform promotes it back to C6. This may improve

	some workloads' performance, but it may also increase power consumption.



.. _intel-idle-enumeration-of-states: