ACPI / sleep: Ignore spurious SCI wakeups from suspend-to-idle

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 (that also helps to catch device-induced
wakeup events occurring during suspend transitions in progress).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index a4327af676fe..e84005d642e6 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -662,14 +662,40 @@ static int acpi_freeze_prepare(void)
 	acpi_os_wait_events_complete();
 	if (acpi_sci_irq_valid())
 		enable_irq_wake(acpi_sci_irq);
+
 	return 0;
 }
 
+static void acpi_freeze_wake(void)
+{
+	/*
+	 * If IRQD_WAKEUP_ARMED is not set for the SCI at this point, it means
+	 * that the SCI has triggered while suspended, so cancel the wakeup in
+	 * case it has not been a wakeup event (the GPEs will be checked later).
+	 */
+	if (acpi_sci_irq_valid() &&
+	    !irqd_is_wakeup_armed(irq_get_irq_data(acpi_sci_irq)))
+		pm_system_cancel_wakeup();
+}
+
+static void acpi_freeze_sync(void)
+{
+	/*
+	 * Process all pending events in case there are any wakeup ones.
+	 *
+	 * The EC driver uses the system workqueue, so that one needs to be
+	 * flushed too.
+	 */
+	acpi_os_wait_events_complete();
+	flush_scheduled_work();
+}
+
 static void acpi_freeze_restore(void)
 {
 	acpi_disable_wakeup_devices(ACPI_STATE_S0);
 	if (acpi_sci_irq_valid())
 		disable_irq_wake(acpi_sci_irq);
+
 	acpi_enable_all_runtime_gpes();
 }
 
@@ -681,6 +707,8 @@ static void acpi_freeze_end(void)
 static const struct platform_freeze_ops acpi_freeze_ops = {
 	.begin = acpi_freeze_begin,
 	.prepare = acpi_freeze_prepare,
+	.wake = acpi_freeze_wake,
+	.sync = acpi_freeze_sync,
 	.restore = acpi_freeze_restore,
 	.end = acpi_freeze_end,
 };