* Arun R Bharadwaj <arun@xxxxxxxxxxxxxxxxxx> [2009-10-16 15:08:50]: This patch adds a little information about the redesigned cpuidle infrastructure in Documentation/cpuidle/core.txt Signed-off-by: Arun R Bharadwaj <arun@xxxxxxxxxxxxxxxxxx> --- Documentation/cpuidle/core.txt | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) Index: linux.trees.git/Documentation/cpuidle/core.txt =================================================================== --- linux.trees.git.orig/Documentation/cpuidle/core.txt +++ linux.trees.git/Documentation/cpuidle/core.txt @@ -21,3 +21,38 @@ which can be used to switch governors at 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. + +Design: + +Cpuidle allows for registration of multiple sets of idle routines. +The latest registered set is used by cpuidle governors as the current +active set to choose the right idle state. This set is managed as a +list and each time the newly registered set is added to the head of the +list and made the current active set. + +An example of how this would work on x86 is shown below. + +----------------- ----------------- +| | | | +| choose b/w | mwait is chosen | mwait | +| mwait, poll, |-------------------------------------> |(current active| +| default, c1e | register to cpuidle | set) | +| | with mwait as the idle routine | | +----------------- ----------------- + + +----------------- ----------------- +| | | c1, c2, c3 | +| ACPI | register to cpuidle | (current) | +| discovery |-------------------------------------> |---------------| +| | with c1, c2, c3 | mwait | +| | as set of idle routines | | +----------------- ----------------- + +With this mechanism, a module can register and unregister its set of +idle routines at run time in a clean manner. + +The main idle routine called inside cpu_idle() of every arch is defined in +driver/cpuidle/cpuidle.c which would in turn call the idle routine selected +by the governor. If the CONFIG_CPU_IDLE is disabled, the arch needs to +provide an alternate definition for cpuidle_idle_call(). -- 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
