• Joseph Lo's avatar
    ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode · 1d328606
    Joseph Lo authored
    The "powered-down" cpuidle mode of Tegra20 needs the CPU0 be the last one
    core to go into this mode before other core. The coupled cpuidle framework
    can help to sync the MPCore to coupled state then go into "powered-down"
    idle mode together. The driver can just assume the MPCore come into
    "powered-down" mode at the same time. No need to take care if the CPU_0
    goes into this mode along and only can put it into safe idle mode (WFI).
    
    The powered-down state of Tegra20 requires power gating both CPU cores.
    When the secondary CPU requests to enter powered-down state, it saves
    its own contexts and then enters WFI for waiting CPU0 in the same state.
    When the CPU0 requests powered-down state, it attempts to put the secondary
    CPU into reset to prevent it from waking up. Then power down both CPUs
    together and power off the cpu rail.
    
    Be aware of that, you may see the legacy power state "LP2" in the code
    which is exactly the same meaning of "CPU power down".
    
    Based on the work by:
    Colin Cross <ccross@android.com>
    Gary King <gking@nvidia.com>
    Signed-off-by: default avatarJoseph Lo <josephl@nvidia.com>
    Acked-by: default avatarColin Cross <ccross@android.com>
    Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
    1d328606
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