• Sudeep Holla's avatar
    cpuidle: dt: assign ->enter_freeze to same as ->enter callback function · a94e502c
    Sudeep Holla authored
    enter_freeze() callback is expected atleast to do the same as enter()
    but it has to guarantee that interrupts aren't enabled at any point
    in its execution, as the tick is frozen.
    CPUs execute ->enter_freeze with the local tick or entire timekeeping
    suspended, so it must not re-enable interrupts at any point (even
    temporarily) or attempt to change states of clock event devices.
    It will be called when the system goes to suspend-to-idle and will
    reduce power usage because CPUs won't be awaken for unnecessary IRQs
    (i.e. woken up only on IRQs from "wakeup sources")
    We can reuse the same code for both the enter() and enter_freeze()
    callbacks as along as they don't re-enable interrupts. Only "coupled"
    cpuidle mechanism enables interrupts and doing that with timekeeping
    suspended is generally not safe.
    Since this generic DT based idle driver doesn't support "coupled"
    states, it is safe to assume that the interrupts are not re-enabled.
    This patch assign enter_freeze to same as enter callback function which
    helps to save power without any intermittent spurious wakeups from
    Signed-off-by: default avatarSudeep Holla <sudeep.holla@arm.com>
    Tested-by: default avatarAndy Gross <andy.gross@linaro.org>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
dt_idle_states.c 6.47 KB