• Rafael J. Wysocki's avatar
    ACPI / PM: Ignore spurious SCI wakeups from suspend-to-idle · 33e4f80e
    Rafael J. Wysocki authored
    The ACPI SCI (System Control Interrupt) is set up as a wakeup IRQ
    during suspend-to-idle transitions and, consequently, any events
    signaled through it wake up the system from that state.  However,
    on some systems some of the events signaled via the ACPI SCI while
    suspended to idle should not cause the system to wake up.  In fact,
    quite often they should just be discarded.
    
    Arguably, systems should not resume entirely on such events, but in
    order to decide which events really should cause the system to resume
    and which are spurious, it is necessary to resume up to the point
    when ACPI SCIs are actually handled and processed, which is after
    executing dpm_resume_noirq() in the system resume path.
    
    For this reasons, add a loop around freeze_enter() in which the
    platforms can process events signaled via multiplexed IRQ lines
    like the ACPI SCI and add suspend-to-idle hooks that can be
    used for this purpose to struct platform_freeze_ops.
    
    In the ACPI case, the ->wake hook is used for checking if the SCI
    has triggered while suspended and deferring the interrupt-induced
    system wakeup until the events signaled through it are actually
    processed sufficiently to decide whether or not the system should
    resume.  In turn, the ->sync hook allows all of the relevant event
    queues to be flushed so as to prevent events from being missed due
    to race conditions.
    
    In addition to that, some ACPI code processing wakeup events needs
    to be modified to use the "hard" version of wakeup triggers, so that
    it will cause a system resume to happen on device-induced wakeup
    events even if the "soft" mechanism to prevent the system from
    suspending is not enabled.  However, to preserve the existing
    behavior with respect to suspend-to-RAM, this only is done in
    the suspend-to-idle case and only if an SCI has occurred while
    suspended.
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    33e4f80e
process.c 5.46 KB