linux-kernel - [PATCH 2/3] PM: runtime: Make put{,_sync}() return 1 when already suspended

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Message-ID: <20250829003319.2785282-2-briannorris@chromium.org>
Date: Thu, 28 Aug 2025 17:28:27 -0700
From: Brian Norris <briannorris@...omium.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
	Pavel Machek <pavel@...nel.org>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	kunit-dev@...glegroups.com,
	Len Brown <lenb@...nel.org>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Brian Norris <briannorris@...omium.org>
Subject: [PATCH 2/3] PM: runtime: Make put{,_sync}() return 1 when already suspended

The pm_runtime.h docs say pm_runtime_put() and pm_runtime_put_sync()
return 1 when already suspended, but this is not true -- they return
-EAGAIN. On the other hand, pm_runtime_put_sync_suspend() and
pm_runtime_put_sync_autosuspend() *do* return 1.

This is an artifact of the fact that the former are built on rpm_idle(),
whereas the latter are built on rpm_suspend().

There are precious few pm_runtime_put()/pm_runtime_put_sync() callers
that check the return code at all, but most of them only log errors, and
usually only for negative error codes. None of them should be treating
this as an error, so:

 * at best, this may fix some case where a driver treats this condition
   as an error, when it shouldn't;

 * at worst, this should make no effect; and

 * somewhere in between, we could potentially clear up non-fatal log
   messages.

Fix the pm_runtime_already_suspended_test() while tweaking the behavior.
The test makes a lot more sense when these all return 1 when the device
is already suspended:

    pm_runtime_put(dev);
    pm_runtime_put_sync(dev);
    pm_runtime_suspend(dev);
    pm_runtime_autosuspend(dev);
    pm_request_autosuspend(dev);
    pm_runtime_put_sync_autosuspend(dev);
    pm_runtime_put_autosuspend(dev);

Signed-off-by: Brian Norris <briannorris@...omium.org>
---

 drivers/base/power/runtime-test.c | 8 ++------
 drivers/base/power/runtime.c      | 3 +++
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/base/power/runtime-test.c b/drivers/base/power/runtime-test.c
index 263c28d5fc50..1be18e871f1d 100644
--- a/drivers/base/power/runtime-test.c
+++ b/drivers/base/power/runtime-test.c
@@ -43,15 +43,11 @@ static void pm_runtime_already_suspended_test(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, 0, pm_runtime_barrier(dev)); /* no wakeup needed */
 
 	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
-	/*
-	 * We never actually left RPM_SUSPENDED, but rpm_idle() still treats
-	 * this as -EAGAIN / "runtime PM status change ongoing".
-	 */
-	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_runtime_put(dev));
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_put(dev));
 
 	pm_runtime_get_noresume(dev);
 	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
-	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_runtime_put_sync(dev));
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_put_sync(dev));
 
 	KUNIT_EXPECT_EQ(test, 1, pm_runtime_suspend(dev));
 	KUNIT_EXPECT_EQ(test, 1, pm_runtime_autosuspend(dev));
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 3e84dc4122de..17cf111d16aa 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -498,6 +498,9 @@ static int rpm_idle(struct device *dev, int rpmflags)
 	if (retval < 0)
 		;	/* Conditions are wrong. */
 
+	else if ((rpmflags & RPM_GET_PUT) && (retval == 1))
+		;	/* put() is allowed in RPM_SUSPENDED */
+
 	/* Idle notifications are allowed only in the RPM_ACTIVE state. */
 	else if (dev->power.runtime_status != RPM_ACTIVE)
 		retval = -EAGAIN;
-- 
2.51.0.318.gd7df087d1a-goog