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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Linux ACPI <linux-acpi@vger.kernel.org>
Cc:     Linux PM <linux-pm@vger.kernel.org>,
        Zhang Rui <rui.zhang@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Chris Chiu <chiu@endlessm.com>,
        Todd Brandt <todd.e.brandt@linux.intel.com>
Subject: [PATCH v2] ACPI: EC: s2idle: Avoid premature returns from acpi_s2idle_wake()
Date:   Sat, 09 May 2020 10:44:41 +0200
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

If the EC GPE status is not set after checking all of the other GPEs,
acpi_s2idle_wake() returns 'false', to indicate that the SCI event
that has just triggered is not a system wakeup one, but it does that
without canceling the pending wakeup and re-arming the SCI for system
wakeup which is a mistake, because it may cause s2idle_loop() to busy
spin until the next valid wakeup event.  [If that happens, the first
spurious wakeup is still pending after acpi_s2idle_wake() has
returned, so s2idle_enter() does nothing, acpi_s2idle_wake()
is called again and it sees that the SCI has triggered, but no GPEs
are active, so 'false' is returned again, and so on.]

Fix that by moving all of the GPE checking logic from
acpi_s2idle_wake() to acpi_ec_dispatch_gpe() and making the
latter return 'true' only if a non-EC GPE has triggered and
'false' otherwise, which will cause acpi_s2idle_wake() to
cancel the pending SCI wakeup and re-arm the SCI for system
wakeup regardless of the EC GPE status.

This also addresses a lockup observed on an Elitegroup EF20EA laptop
after attempting to wake it up from suspend-to-idle by a key press.

Fixes: d5406284ff80 ("ACPI: PM: s2idle: Refine active GPEs check")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=207603
Reported-by: Todd Brandt <todd.e.brandt@linux.intel.com>
Fixes: fdde0ff8590b ("ACPI: PM: s2idle: Prevent spurious SCIs from waking up the system")
Link: https://lore.kernel.org/linux-acpi/CAB4CAwdqo7=MvyG_PE+PGVfeA17AHF5i5JucgaKqqMX6mjArbQ@mail.gmail.com/
Reported-by: Chris Chiu <chiu@endlessm.com>
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

-> v2:
   * Improve the changelog and add more tags.

---
 drivers/acpi/ec.c       |   24 ++++++++++++++++--------
 drivers/acpi/internal.h |    1 -
 drivers/acpi/sleep.c    |   14 ++------------
 3 files changed, 18 insertions(+), 21 deletions(-)

Index: linux-pm/drivers/acpi/sleep.c
===================================================================
--- linux-pm.orig/drivers/acpi/sleep.c
+++ linux-pm/drivers/acpi/sleep.c
@@ -1013,21 +1013,11 @@ static bool acpi_s2idle_wake(void)
 		if (acpi_check_wakeup_handlers())
 			return true;
 
-		/*
-		 * If the status bit is set for any enabled GPE other than the
-		 * EC one, the wakeup is regarded as a genuine one.
-		 */
-		if (acpi_ec_other_gpes_active())
+		/* Check non-EC GPE wakeups and dispatch the EC GPE. */
+		if (acpi_ec_dispatch_gpe())
 			return true;
 
 		/*
-		 * If the EC GPE status bit has not been set, the wakeup is
-		 * regarded as a spurious one.
-		 */
-		if (!acpi_ec_dispatch_gpe())
-			return false;
-
-		/*
 		 * Cancel the wakeup and process all pending events in case
 		 * there are any wakeup ones in there.
 		 *
Index: linux-pm/drivers/acpi/ec.c
===================================================================
--- linux-pm.orig/drivers/acpi/ec.c
+++ linux-pm/drivers/acpi/ec.c
@@ -1994,23 +1994,31 @@ void acpi_ec_set_gpe_wake_mask(u8 action
 		acpi_set_gpe_wake_mask(NULL, first_ec->gpe, action);
 }
 
-bool acpi_ec_other_gpes_active(void)
-{
-	return acpi_any_gpe_status_set(first_ec ? first_ec->gpe : U32_MAX);
-}
-
 bool acpi_ec_dispatch_gpe(void)
 {
 	u32 ret;
 
 	if (!first_ec)
+		return acpi_any_gpe_status_set(U32_MAX);
+
+	/*
+	 * Report wakeup if the status bit is set for any enabled GPE other
+	 * than the EC one.
+	 */
+	if (acpi_any_gpe_status_set(first_ec->gpe))
+		return true;
+
+	if (ec_no_wakeup)
 		return false;
 
+	/*
+	 * Dispatch the EC GPE in-band, but do not report wakeup in any case
+	 * to allow the caller to process events properly after that.
+	 */
 	ret = acpi_dispatch_gpe(NULL, first_ec->gpe);
-	if (ret == ACPI_INTERRUPT_HANDLED) {
+	if (ret == ACPI_INTERRUPT_HANDLED)
 		pm_pr_dbg("EC GPE dispatched\n");
-		return true;
-	}
+
 	return false;
 }
 #endif /* CONFIG_PM_SLEEP */
Index: linux-pm/drivers/acpi/internal.h
===================================================================
--- linux-pm.orig/drivers/acpi/internal.h
+++ linux-pm/drivers/acpi/internal.h
@@ -202,7 +202,6 @@ void acpi_ec_remove_query_handler(struct
 
 #ifdef CONFIG_PM_SLEEP
 void acpi_ec_flush_work(void);
-bool acpi_ec_other_gpes_active(void);
 bool acpi_ec_dispatch_gpe(void);
 #endif