• Daniel Lezcano's avatar
    cpuidle: support multiple drivers · bf4d1b5d
    Daniel Lezcano authored
    With the tegra3 and the big.LITTLE [1] new architectures, several cpus
    with different characteristics (latencies and states) can co-exists on the
    system.
    
    The cpuidle framework has the limitation of handling only identical cpus.
    
    This patch removes this limitation by introducing the multiple driver support
    for cpuidle.
    
    This option is configurable at compile time and should be enabled for the
    architectures mentioned above. So there is no impact for the other platforms
    if the option is disabled. The option defaults to 'n'. Note the multiple drivers
    support is also compatible with the existing drivers, even if just one driver is
    needed, all the cpu will be tied to this driver using an extra small chunk of
    processor memory.
    
    The multiple driver support use a per-cpu driver pointer instead of a global
    variable and the accessor to this variable are done from a cpu context.
    
    In order to keep the compatibility with the existing drivers, the function
    'cpuidle_register_driver' and 'cpuidle_unregister_driver' will register
    the specified driver for all the cpus.
    
    The semantic for the output of /sys/devices/system/cpu/cpuidle/current_driver
    remains the same except the driver name will be related to the current cpu.
    
    The /sys/devices/system/cpu/cpu[0-9]/cpuidle/driver/name files are added
    allowing to read the per cpu driver name.
    
    [1] http://lwn.net/Articles/481055/
    
    
    
    Signed-off-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
    Acked-by: default avatarPeter De Schrijver <pdeschrijver@nvidia.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    bf4d1b5d