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Commit 4e3d0319 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 

* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
  ACPI: DMI: quirk for FSC ESPRIMO Mobile V5505
  ACPI: DMI blacklist updates
  pnpacpi: __initdata is not an identifier
  ACPI: static acpi_chain_head
  ACPI: static acpi_find_dsdt_initrd()
  ACPI: static acpi_no_initrd_override_setup()
  thinkpad_acpi: static
  ACPI suspend: Execute _WAK with the right argument
  cpuidle: Add Documentation
  ACPI, cpuidle: Clarify C-state description in sysfs
  ACPI: fix suspend regression due to idle update
parents 11d64be6 f60d63f6

Documentation/00-INDEX

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@@ -109,6 +109,8 @@ cpu-hotplug.txt 
	- document describing CPU hotplug support in the Linux kernel.

	- document describing CPU hotplug support in the Linux kernel.

cpu-load.txt

cpu-load.txt

	- document describing how CPU load statistics are collected.

	- document describing how CPU load statistics are collected.

cpuidle/

	- info on CPU_IDLE, CPU idle state management subsystem.

cpusets.txt

cpusets.txt

	- documents the cpusets feature; assign CPUs and Mem to a set of tasks.

	- documents the cpusets feature; assign CPUs and Mem to a set of tasks.

cputopology.txt

cputopology.txt

Documentation/cpuidle/core.txt

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		Supporting multiple CPU idle levels in kernel



				cpuidle



General Information:



Various CPUs today support multiple idle levels that are differentiated

by varying exit latencies and power consumption during idle.

cpuidle is a generic in-kernel infrastructure that separates

idle policy (governor) from idle mechanism (driver) and provides a

standardized infrastructure to support independent development of

governors and drivers.



cpuidle resides under drivers/cpuidle.



Boot options:

"cpuidle_sysfs_switch"

enables current_governor interface in /sys/devices/system/cpu/cpuidle/,

which can be used to switch governors at run time. This boot option

is meant for developer testing only. In normal usage, kernel picks the

best governor based on governor ratings.

SEE ALSO: sysfs.txt in this directory.

Documentation/cpuidle/driver.txt

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		Supporting multiple CPU idle levels in kernel



				cpuidle drivers









cpuidle driver hooks into the cpuidle infrastructure and handles the

architecture/platform dependent part of CPU idle states. Driver

provides the platform idle state detection capability and also

has mechanisms in place to support actual entry-exit into CPU idle states.



cpuidle driver initializes the cpuidle_device structure for each CPU device

and registers with cpuidle using cpuidle_register_device.



It can also support the dynamic changes (like battery <-> AC), by using

cpuidle_pause_and_lock, cpuidle_disable_device and cpuidle_enable_device,

cpuidle_resume_and_unlock.



Interfaces:

extern int cpuidle_register_driver(struct cpuidle_driver *drv);

extern void cpuidle_unregister_driver(struct cpuidle_driver *drv);

extern int cpuidle_register_device(struct cpuidle_device *dev);

extern void cpuidle_unregister_device(struct cpuidle_device *dev);



extern void cpuidle_pause_and_lock(void);

extern void cpuidle_resume_and_unlock(void);

extern int cpuidle_enable_device(struct cpuidle_device *dev);

extern void cpuidle_disable_device(struct cpuidle_device *dev);

Documentation/cpuidle/governor.txt

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		Supporting multiple CPU idle levels in kernel



				cpuidle governors









cpuidle governor is policy routine that decides what idle state to enter at

any given time. cpuidle core uses different callbacks to the governor.



* enable() to enable governor for a particular device

* disable() to disable governor for a particular device

* select() to select an idle state to enter

* reflect() called after returning from the idle state, which can be used

  by the governor for some record keeping.



More than one governor can be registered at the same time and

users can switch between drivers using /sysfs interface (when enabled).

More than one governor part is supported for developers to easily experiment

with different governors. By default, most optimal governor based on your

kernel configuration and platform will be selected by cpuidle.



Interfaces:

extern int cpuidle_register_governor(struct cpuidle_governor *gov);

extern void cpuidle_unregister_governor(struct cpuidle_governor *gov);

struct cpuidle_governor

Documentation/cpuidle/sysfs.txt

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		Supporting multiple CPU idle levels in kernel



				cpuidle sysfs



System global cpuidle related information and tunables are under

/sys/devices/system/cpu/cpuidle



The current interfaces in this directory has self-explanatory names:

* current_driver

* current_governor_ro



With cpuidle_sysfs_switch boot option (meant for developer testing)

following objects are visible instead.

* current_driver

* available_governors

* current_governor

In this case users can switch the governor at run time by writing

to current_governor.





Per logical CPU specific cpuidle information are under

/sys/devices/system/cpu/cpuX/cpuidle

for each online cpu X



--------------------------------------------------------------------------------

# ls -lR /sys/devices/system/cpu/cpu0/cpuidle/

/sys/devices/system/cpu/cpu0/cpuidle/:

total 0

drwxr-xr-x 2 root root 0 Feb  8 10:42 state0

drwxr-xr-x 2 root root 0 Feb  8 10:42 state1

drwxr-xr-x 2 root root 0 Feb  8 10:42 state2

drwxr-xr-x 2 root root 0 Feb  8 10:42 state3



/sys/devices/system/cpu/cpu0/cpuidle/state0:

total 0

-r--r--r-- 1 root root 4096 Feb  8 10:42 desc

-r--r--r-- 1 root root 4096 Feb  8 10:42 latency

-r--r--r-- 1 root root 4096 Feb  8 10:42 name

-r--r--r-- 1 root root 4096 Feb  8 10:42 power

-r--r--r-- 1 root root 4096 Feb  8 10:42 time

-r--r--r-- 1 root root 4096 Feb  8 10:42 usage



/sys/devices/system/cpu/cpu0/cpuidle/state1:

total 0

-r--r--r-- 1 root root 4096 Feb  8 10:42 desc

-r--r--r-- 1 root root 4096 Feb  8 10:42 latency

-r--r--r-- 1 root root 4096 Feb  8 10:42 name

-r--r--r-- 1 root root 4096 Feb  8 10:42 power

-r--r--r-- 1 root root 4096 Feb  8 10:42 time

-r--r--r-- 1 root root 4096 Feb  8 10:42 usage



/sys/devices/system/cpu/cpu0/cpuidle/state2:

total 0

-r--r--r-- 1 root root 4096 Feb  8 10:42 desc

-r--r--r-- 1 root root 4096 Feb  8 10:42 latency

-r--r--r-- 1 root root 4096 Feb  8 10:42 name

-r--r--r-- 1 root root 4096 Feb  8 10:42 power

-r--r--r-- 1 root root 4096 Feb  8 10:42 time

-r--r--r-- 1 root root 4096 Feb  8 10:42 usage



/sys/devices/system/cpu/cpu0/cpuidle/state3:

total 0

-r--r--r-- 1 root root 4096 Feb  8 10:42 desc

-r--r--r-- 1 root root 4096 Feb  8 10:42 latency

-r--r--r-- 1 root root 4096 Feb  8 10:42 name

-r--r--r-- 1 root root 4096 Feb  8 10:42 power

-r--r--r-- 1 root root 4096 Feb  8 10:42 time

-r--r--r-- 1 root root 4096 Feb  8 10:42 usage

--------------------------------------------------------------------------------





* desc : Small description about the idle state (string)

* latency : Latency to exit out of this idle state (in microseconds)

* name : Name of the idle state (string)

* power : Power consumed while in this idle state (in milliwatts)

* time : Total time spent in this idle state (in microseconds)

* usage : Number of times this state was entered (count)