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Subject[PATCH v5] Documentation/ABI: update cpuidle sysfs documentation
Update cpuidle documentation using git logs and existing documentation
in Documentation/cpuidle/sysfs.txt. This might be useful for scripting
and tracking changes in the ABI.

Signed-off-by: Aishwarya Pant <>
Changes in v5:
- Update contact information- LKML -> power management mailing list
- Fix patch formatting
- Fix subject line
- Merge cpuidle_sysfs_switch attributes' description with the previous

Documentation/ABI/testing/sysfs-devices-system-cpu | 77 +++++++++++++++++++++-
1 file changed, 75 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index bfd29bc8d37a..4ed63b6cfb15 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -108,6 +108,8 @@ Description: CPU topology files that describe a logical CPU's relationship

What: /sys/devices/system/cpu/cpuidle/current_driver
+ /sys/devices/system/cpu/cpuidle/available_governors
+ /sys/devices/system/cpu/cpuidle/current_governor
Date: September 2007
Contact: Linux kernel mailing list <>
Description: Discover cpuidle policy and mechanism
@@ -119,13 +121,84 @@ Description: Discover cpuidle policy and mechanism
Idle policy (governor) is differentiated from idle mechanism

- current_driver: displays current idle mechanism
+ current_driver: (RO) displays current idle mechanism

- current_governor_ro: displays current idle policy
+ current_governor_ro: (RO) displays current idle policy
+ With the cpuidle_sysfs_switch boot option enabled (meant for
+ developer testing), the following three attributes are visible
+ instead:
+ current_driver: same as described above
+ available_governors: (RO) displays a space separated list of
+ available governors
+ current_governor: (RW) displays current idle policy. Users can
+ switch the governor at runtime by writing to this file.

See files in Documentation/cpuidle/ for more information.

+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/name
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
+Date: September 2007
+KernelVersion: v2.6.24
+Contact: Linux power management list <>
+ The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
+ logical CPU specific cpuidle information for each online cpu X.
+ The processor idle states which are available for use have the
+ following attributes:
+ name: (RO) Name of the idle state (string).
+ latency: (RO) The latency to exit out of this idle state (in
+ microseconds).
+ power: (RO) The power consumed while in this idle state (in
+ milliwatts).
+ time: (RO) The total time spent in this idle state (in microseconds).
+ usage: (RO) Number of times this state was entered (a count).
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/desc
+Date: February 2008
+KernelVersion: v2.6.25
+Contact: Linux power management list <>
+ (RO) A small description about the idle state (string).
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/disable
+Date: March 2012
+KernelVersion: v3.10
+Contact: Linux power management list <>
+ (RW) Option to disable this idle state (bool). The behavior and
+ the effect of the disable variable depends on the implementation
+ of a particular governor. In the ladder governor, for example,
+ it is not coherent, i.e. if one is disabling a light state, then
+ all deeper states are disabled as well, but the disable variable
+ does not reflect it. Likewise, if one enables a deep state but a
+ lighter state still is disabled, then this has no effect.
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/residency
+Date: March 2014
+KernelVersion: v3.15
+Contact: Linux power management list <>
+ (RO) Display the target residency i.e. the minimum amount of
+ time (in microseconds) this cpu should spend in this idle state
+ to make the transition worth the effort.
What: /sys/devices/system/cpu/cpu#/cpufreq/*
Date: pre-git history
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