Documentation for cpuidle infrastructure. This patch was submitted once a while back. But, somehow got dropped or never made it upstream. Resending with updates. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx> Index: linux-2.6.25-rc/Documentation/cpuidle/core.txt =================================================================== --- /dev/null +++ linux-2.6.25-rc/Documentation/cpuidle/core.txt @@ -0,0 +1,17 @@ + + 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. + + Index: linux-2.6.25-rc/Documentation/cpuidle/driver.txt =================================================================== --- /dev/null +++ linux-2.6.25-rc/Documentation/cpuidle/driver.txt @@ -0,0 +1,32 @@ + + + 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); + Index: linux-2.6.25-rc/Documentation/cpuidle/sysfs.txt =================================================================== --- /dev/null +++ linux-2.6.25-rc/Documentation/cpuidle/sysfs.txt @@ -0,0 +1,81 @@ + + + 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 user can switch the governor at run time by writing +onto 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) + + Index: linux-2.6.25-rc/Documentation/cpuidle/governor.txt =================================================================== --- /dev/null +++ linux-2.6.25-rc/Documentation/cpuidle/governor.txt @@ -0,0 +1,30 @@ + + + + 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 +user 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 + Index: linux-2.6.25-rc/Documentation/00-INDEX =================================================================== --- linux-2.6.25-rc.orig/Documentation/00-INDEX +++ linux-2.6.25-rc/Documentation/00-INDEX @@ -106,6 +106,8 @@ cpu-hotplug.txt - document describing CPU hotplug support in the Linux kernel. cpu-load.txt - document describing how CPU load statistics are collected. +cpuidle/ + - info on CPU_IDLE, CPU idle state management subsystem. cpusets.txt - documents the cpusets feature; assign CPUs and Mem to a set of tasks. cputopology.txt - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
