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    Subject[PATCH 0/2]: cpuidle: Introducing cpuidle infrastructure to powerpc.

    **** RFC not for inclusion ****

    "Cpuidle" is a CPU Power Management infrastrusture which helps manage
    idle CPUs in a clean and efficient manner. The architecture can register
    its driver (in this case, tpmd_idle driver) so that it subscribes for
    cpuidle feature. Cpuidle has a set of governors (ladder and menu),
    which will decide the best idle state to be chosen for the current situation,
    based on heuristics, and calculates the expected residency time
    for the current idle state. So based on this, the cpu is put into
    the right idle state.

    Currently, cpuidle infrasture is exploited by ACPI to choose between
    the available ACPI C-states. This patch-set is aimed at enabling
    cpuidle for powerpc and provides a sample implementation for pseries.

    Currently, in the pseries_dedicated_idle_sleep(), the processor would
    poll for a time period, which is called the snooze, and only then it
    is ceded, which would put the processor in nap state. Cpuidle aims at
    separating this into 2 different idle states. Based on the expected
    residency time predicted by the cpuidle governor, the idle state is
    chosen directly. So, choosing to enter the nap state directly based on
    the decision made by cpuidle would avoid unnecessary snoozing before
    entering nap.

    This patch-set tries to achieve the above objective by introducing a
    Thermal and Power Management Device module called tpmd_idle in
    arch/powerpc/platform/pseries/tpmd_idle.c, which implements cpuidle
    idle loop which would replace the pseries_dedicated_idle_sleep()
    when cpuidle is enabled.

    Patches included in this set:
    PATCH 1/2 - Enable cpuidle for pSeries.
    PATCH 2/2 - Implement Thermal & Power Management Devices(TPMD) idle module

    Any feedback on the overall design and idea is immensely valuable.


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