[PATCH v5] ACPI: button: Report wakeup key only for power button wakeups

[Baorui.Liu <baorliu@amd.com>]

The ACPI button driver reports KEY_WAKEUP from the Power Button input
device to let userspace know that the system was resumed by a power
button wakeup.

However, reporting KEY_WAKEUP from generic system resume paths can make
userspace observe a Power Button wakeup even when the system was resumed
by a different wake source.

This is reproducible on an AMD Android 15 Xen guest. With a kernel
without this fix, a non-power-button S3 resume:

  echo mem > /sys/power/state
  xl trigger android s3resume

makes the Power Button input device report KEY_WAKEUP. The same test on
a kernel with this fix no longer reports KEY_WAKEUP from the Power Button
input device.

Track whether a power button event/notify is observed while the ACPI
button device is suspended, and report KEY_WAKEUP on resume only in that
case.

When the fixed power-button status bit is set during early S3 resume,
clear it to avoid a deferred KEY_POWER delivery to userspace, and mark
wakeup_pending so button resume can still report KEY_WAKEUP. Also clear
wakeup_pending before setting suspended to avoid a race with a power
button SCI during suspend entry.

Declare acpi_button_power_wakeup_pending() with IS_REACHABLE so that
CONFIG_ACPI_BUTTON=m does not leave an unresolved reference in built-in
sleep.c.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202609290454.LJrhMCb3-lkp@intel.com/
Signed-off-by: Baorui.Liu <baorliu@amd.com>
---
Changes since v4:
- Fix LKP build ERROR when CONFIG_ACPI_BUTTON=m by declaring
  acpi_button_power_wakeup_pending() with IS_REACHABLE().

 drivers/acpi/button.c | 46 ++++++++++++++++++++++++++++++++++++++++++-
 drivers/acpi/sleep.c  | 27 +++++++++++--------------
 include/acpi/button.h | 13 ++++++++++++
 3 files changed, 70 insertions(+), 16 deletions(-)

diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
index cdbb1023a8ee..c07de417df5d 100644
--- a/drivers/acpi/button.c
+++ b/drivers/acpi/button.c
@@ -191,6 +191,7 @@ struct acpi_button {
 	bool last_state;
 	ktime_t last_time;
 	bool suspended;
+	bool wakeup_pending;
 	bool lid_state_initialized;
 	bool gpe_enabled;
 };
@@ -397,6 +398,34 @@ static void acpi_lid_forget(struct acpi_device *adev)
 }
 
 /* Driver Interface */
+/**
+ * acpi_button_power_wakeup_pending - Mark fixed power button wakeup pending.
+ *
+ * Used when the fixed power-button status bit is observed and cleared during
+ * early S3 resume, so KEY_WAKEUP can still be reported from button resume
+ * without delivering a deferred KEY_POWER to userspace.
+ */
+void acpi_button_power_wakeup_pending(void)
+{
+	struct acpi_device *adev;
+	struct device *phys_dev;
+	struct acpi_button *button;
+
+	adev = acpi_dev_get_first_match_dev(ACPI_BUTTON_HID_POWERF, NULL, -1);
+	if (!adev)
+		return;
+
+	phys_dev = acpi_get_first_physical_node(adev);
+	if (phys_dev) {
+		button = dev_get_drvdata(phys_dev);
+		if (button && button->type == ACPI_BUTTON_TYPE_POWER)
+			button->wakeup_pending = true;
+	}
+
+	acpi_dev_put(adev);
+}
+EXPORT_SYMBOL_GPL(acpi_button_power_wakeup_pending);
+
 int acpi_lid_open(void)
 {
 	guard(mutex)(&acpi_lid_lock);
@@ -476,6 +505,9 @@ static void acpi_button_notify(acpi_handle handle, u32 event, void *data)
 
 	acpi_pm_wakeup_event(button->dev);
 
+	if (button->type == ACPI_BUTTON_TYPE_POWER && button->suspended)
+		button->wakeup_pending = true;
+
 	if (button->suspended || event == ACPI_BUTTON_NOTIFY_WAKE)
 		return;
 
@@ -498,6 +530,11 @@ static void acpi_button_notify_run(void *data)
 
 static u32 acpi_button_event(void *data)
 {
+	struct acpi_button *button = data;
+
+	if (button->type == ACPI_BUTTON_TYPE_POWER && button->suspended)
+		button->wakeup_pending = true;
+
 	acpi_os_execute(OSL_NOTIFY_HANDLER, acpi_button_notify_run, data);
 	return ACPI_INTERRUPT_HANDLED;
 }
@@ -507,6 +544,12 @@ static int acpi_button_suspend(struct device *dev)
 {
 	struct acpi_button *button = dev_get_drvdata(dev);
 
+	/*
+	 * Clear wakeup_pending before marking suspended. Otherwise a power
+	 * button SCI between the two stores could set wakeup_pending and then
+	 * be overwritten here, losing a real wakeup.
+	 */
+	button->wakeup_pending = false;
 	button->suspended = true;
 	return 0;
 }
@@ -523,12 +566,13 @@ static int acpi_button_resume(struct device *dev)
 		acpi_lid_initialize_state(button);
 	}
 
-	if (button->type == ACPI_BUTTON_TYPE_POWER) {
+	if (button->type == ACPI_BUTTON_TYPE_POWER && button->wakeup_pending) {
 		input = button->input;
 		input_report_key(input, KEY_WAKEUP, 1);
 		input_sync(input);
 		input_report_key(input, KEY_WAKEUP, 0);
 		input_sync(input);
+		button->wakeup_pending = false;
 	}
 	return 0;
 }
diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index 132a9df98471..30e268987e37 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -22,6 +22,7 @@
 #include <linux/syscore_ops.h>
 #include <asm/io.h>
 #include <trace/events/power.h>
+#include <acpi/button.h>
 
 #include "internal.h"
 #include "sleep.h"
@@ -504,12 +505,11 @@ static void acpi_pm_finish(void)
 
 	acpi_resume_power_resources();
 
-	/* If we were woken with the fixed power button, provide a small
-	 * hint to userspace in the form of a wakeup event on the fixed power
-	 * button device (if it can be found).
-	 *
-	 * We delay the event generation til now, as the PM layer requires
-	 * timekeeping to be running before we generate events. */
+	/*
+	 * If woken by the fixed power button, provide a wakeup event on that
+	 * device. KEY_WAKEUP input reporting is handled by the button driver
+	 * via wakeup_pending; do not synthesize KEY_POWER here.
+	 */
 	if (!pwr_btn_event_pending)
 		return;
 
@@ -626,14 +626,11 @@ static int acpi_suspend_enter(suspend_state_t pm_state)
 	/* Reprogram control registers */
 	acpi_leave_sleep_state_prep(acpi_state);
 
-	/* ACPI 3.0 specs (P62) says that it's the responsibility
-	 * of the OSPM to clear the status bit [ implying that the
-	 * POWER_BUTTON event should not reach userspace ]
-	 *
-	 * However, we do generate a small hint for userspace in the form of
-	 * a wakeup event. We flag this condition for now and generate the
-	 * event later, as we're currently too early in resume to be able to
-	 * generate wakeup events.
+	/*
+	 * ACPI 3.0 (P62): OSPM should clear the fixed power-button status bit
+	 * so the event does not reach userspace as KEY_POWER. Remember that a
+	 * power-button wake occurred so button resume can report KEY_WAKEUP
+	 * and acpi_pm_finish() can emit a PM wakeup event.
 	 */
 	if (ACPI_SUCCESS(status) && (acpi_state == ACPI_STATE_S3)) {
 		acpi_event_status pwr_btn_status = ACPI_EVENT_FLAG_DISABLED;
@@ -642,8 +639,8 @@ static int acpi_suspend_enter(suspend_state_t pm_state)
 
 		if (pwr_btn_status & ACPI_EVENT_FLAG_STATUS_SET) {
 			acpi_clear_event(ACPI_EVENT_POWER_BUTTON);
-			/* Flag for later */
 			pwr_btn_event_pending = true;
+			acpi_button_power_wakeup_pending();
 		}
 	}
 
diff --git a/include/acpi/button.h b/include/acpi/button.h
index af2fce5d2ee3..c909c00664c7 100644
--- a/include/acpi/button.h
+++ b/include/acpi/button.h
@@ -15,4 +15,17 @@ static inline int acpi_lid_open(void)
 }
 #endif /* IS_ENABLED(CONFIG_ACPI_BUTTON) */
 
+/*
+ * sleep.c is built-in and calls this helper. Use IS_REACHABLE so that when
+ * CONFIG_ACPI_BUTTON=m the call site gets an inline stub instead of an
+ * unresolved vmlinux link reference (0day/LKP ERROR).
+ */
+#if IS_REACHABLE(CONFIG_ACPI_BUTTON)
+extern void acpi_button_power_wakeup_pending(void);
+#else
+static inline void acpi_button_power_wakeup_pending(void)
+{
+}
+#endif /* IS_REACHABLE(CONFIG_ACPI_BUTTON) */
+
 #endif /* ACPI_BUTTON_H */

base-commit: 4a819ee5f2834330656d6ac168c4c8cf27fdeec2
-- 
2.34.1