PM: Block enabling of runtime PM during system suspend

If device_prepare() runs on a device that has never had runtime
PM enabled so far, it may reasonably assume that runtime PM will
not be enabled for that device during the system suspend-resume
cycle currently in progress, but this has never been guaranteed.

To verify this assumption, make device_prepare() arrange for
triggering a device warning accompanied by a call trace dump if
runtime PM is enabled for such a device after it has returned.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/6131109.lOV4Wx5bFT@rjwysocki.net

1 files changed, 24 insertions, 0 deletions

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index a5aed89e1a6b..797ea38ceba7 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1460,6 +1460,26 @@ int pm_runtime_barrier(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(pm_runtime_barrier);
 
+void pm_runtime_block_if_disabled(struct device *dev)
+{
+	spin_lock_irq(&dev->power.lock);
+
+	if (dev->power.disable_depth && dev->power.last_status == RPM_INVALID)
+		dev->power.last_status = RPM_BLOCKED;
+
+	spin_unlock_irq(&dev->power.lock);
+}
+
+void pm_runtime_unblock(struct device *dev)
+{
+	spin_lock_irq(&dev->power.lock);
+
+	if (dev->power.last_status == RPM_BLOCKED)
+		dev->power.last_status = RPM_INVALID;
+
+	spin_unlock_irq(&dev->power.lock);
+}
+
 void __pm_runtime_disable(struct device *dev, bool check_resume)
 {
 	spin_lock_irq(&dev->power.lock);
@@ -1518,6 +1538,10 @@ void pm_runtime_enable(struct device *dev)
 	if (--dev->power.disable_depth > 0)
 		goto out;
 
+	if (dev->power.last_status == RPM_BLOCKED) {
+		dev_warn(dev, "Attempt to enable runtime PM when it is blocked\n");
+		dump_stack();
+	}
 	dev->power.last_status = RPM_INVALID;
 	dev->power.accounting_timestamp = ktime_get_mono_fast_ns();