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    Subject[RFC PATCH V4 0/4] cpuidle: global registration of idle states with per-cpu statistics
    The following patch series implements global registration of cpuidle
    states, and also has the necessary data structure changes to
    accommodate the per-cpu writable members of the cpuidle_states

    Previous version of the series (V3) is at

    This series applies on 2.6.39-rc5 with Len Brown's pm_idle() cleanup
    version 3 ( plus the patch

    Changes from previous version (V3):

    1. Compile tested for ARM using the following configs: da8xx_omapl_defconfig,
    kirkwood_defconfig, stamp9g20_defconfig, omap2plus_defconfig. Boot tested on
    Panda SoC (OMAP4430) but it doesn't really use cpuidle.

    2. Boot tested on x86 nehalem with multiple C-states for both intel_idle
    and acpi_idle drivers.

    3. Boot tested on T60p thinkpad that has T2600 cpu with multiple C-states.
    Additionally tested the case when C-state tables change on
    AC <-> Battery power switch.

    4. De-duplicated code in [1/4] and moved common code related to
    update of cpuidle statistics to drivers/cpuidle/cpuidle.c

    5. Handled the case when acpi_processor_cst_has_changed() is called on x86
    on switching power from AC <-> Battery. The implementation is just
    a prototype. Please provide suggestions.

    Brief description of the patches:

    The core change in this series is to split the cpuidle_device structure
    into parts that can be global and parts that has to remain per-cpu.
    The per-cpu pieces are mostly generic statistics that can be independent
    of current running driver. As a result of these changes, there is single
    copy of cpuidle_states structure and single registration done by one
    cpu. The low level driver is free to set per-cpu driver data on
    each cpu if needed using the cpuidle_set_statedata() as the case
    today. Only in very rare cases asymmetric C-states exist which can be
    handled within the cpuidle driver. Most architectures do not have
    asymmetric C-states.

    First two patches in the series facilitate splitting of cpuidle_states
    and cpuidle_device structure and next two patches do the actual split,
    change the API's and make existing code follow the changed API.

    [1/4] - Move the idle residency accounting part from cpuidle.c to
    the respective low level drivers, so that the accounting can
    be accurately maintained if the driver decides to demote the
    chosen (suggested) by the governor.

    [2/4] - removes the cpuidle_device()->prepare API since is is not
    widely used and the only use case was to allow software
    demotion using CPUIDLE_FLAG_IGNORE flag. Both these
    functions can be absorbed within the cpuidle back-end
    driver ad hence deprecating the prepare routine and the

    - Ref:

    [3/4] - Splits the usage statistics (read/write) part out of
    cpuidle_state structure, so that the states can become read
    only and hence made global.

    [4/4] - most APIs will now need to pass pointer to both global
    cpuidle_driver and per-cpu cpuidle_device structure.


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