[PATCH v4 1/5] PM: wakeup: Add out-of-band system wakeup support for devices

Peng Fan
2025-09-22T02:21:29Z

Some devices can wake up the system from suspend even when their power
domains are turned off. This is possible because their system-wakeup logic
resides in an always-on power domain - indicating that they support
out-of-band system wakeup.

Currently, PM domain core doesn't power off such devices if they are marked
as system wakeup sources. To better represent devices with out-of-band
wakeup capability, this patch introduces a new flag out_band_wakeup in
'struct dev_pm_info'.

Two helper APIs are added:
- device_set_out_band_wakeup() - to mark a device as having out-of-band
wakeup capability.
- device_out_band_wakeup() - to query the flag.

Allow the PM core and drivers to distinguish between regular and
out-of-band wakeup sources, enable more accurate power management decision.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
drivers/base/power/main.c | 1 +
include/linux/pm.h | 1 +
include/linux/pm_wakeup.h | 17 +++++++++++++++++
3 files changed, 19 insertions(+)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index b9a34c3425ecfab038097e2c03645157af2e598c..6b1ca729dc3e34292952c9c309aab3f34a0a664a 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -2124,6 +2124,7 @@ static int device_prepare(struct device *dev, pm_message_t state)
device_lock(dev);

dev->power.wakeup_path = false;
+ dev->power.out_band_wakeup = false;

if (dev->power.no_pm_callbacks)
goto unlock;
diff --git a/include/linux/pm.h b/include/linux/pm.h
index cc7b2dc28574c24ece2f651352d4d23ecaf15f31..5b28a4f2e87e2aa34acc709e146ce729acace344 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -684,6 +684,7 @@ struct dev_pm_info {
bool smart_suspend:1; /* Owned by the PM core */
bool must_resume:1; /* Owned by the PM core */
bool may_skip_resume:1; /* Set by subsystems */
+ bool out_band_wakeup:1;
bool strict_midlayer:1;
#else
bool should_wakeup:1;
diff --git a/include/linux/pm_wakeup.h b/include/linux/pm_wakeup.h
index c838b4a30f876ef5a66972d16f461cfba9ff2814..41e8f344a20563898e827da62dd240b8cbe657d2 100644
--- a/include/linux/pm_wakeup.h
+++ b/include/linux/pm_wakeup.h
@@ -94,6 +94,16 @@ static inline void device_set_wakeup_path(struct device *dev)
dev->power.wakeup_path = true;
}

+static inline void device_set_out_band_wakeup(struct device *dev)
+{
+ dev->power.out_band_wakeup = true;
+}
+
+static inline bool device_out_band_wakeup(struct device *dev)
+{
+ return dev->power.out_band_wakeup;
+}
+
/* drivers/base/power/wakeup.c */
extern struct wakeup_source *wakeup_source_register(struct device *dev,
const char *name);
@@ -162,6 +172,13 @@ static inline bool device_wakeup_path(struct device *dev)

static inline void device_set_wakeup_path(struct device *dev) {}

+static inline void device_set_out_band_wakeup(struct device *dev) {}
+
+static inline bool device_out_band_wakeup(struct device *dev)
+{
+ return false;
+}
+
static inline void __pm_stay_awake(struct wakeup_source *ws) {}

static inline void pm_stay_awake(struct device *dev) {}

--
2.37.1