[PATCH] driver core: Call pm_runtime_put_sync() only after device_remove()

Uwe Kleine-König
2023-05-11T07:35:26Z

Many drivers that use runtime PM call pm_runtime_get_sync() or one of
its variants in their remove callback. So calling pm_runtime_put_sync()
directly before calling the remove callback results (under some
conditions) in the driver's suspend routine being called just to resume
it again afterwards.

So delay the pm_runtime_put_sync() call until after device_remove().

Confirmed on a stm32mp157a that doing

echo 4400e000.can > /sys/bus/platform/drivers/m_can_platform/unbind

(starting with a runtime-pm suspended 4400e000.can) results in one call
less of m_can_runtime_resume() and m_can_runtime_suspend() each after
this change was applied.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
Hello,

side note: To test I added a dev_info() to m_can_runtime_resume() and
m_can_runtime_suspend(). I was surprised that directly after boot I had:

# dmesg | grep -E '4400e000.can: m_can_runtime_(resume|suspend)' | wc -l
15

I didn't go down that rabbit hole to debug this.

Best regards
Uwe

drivers/base/dd.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 9c09ca5c4ab6..d97f6b1486d1 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -1267,10 +1267,10 @@ static void __device_release_driver(struct device *dev, struct device *parent)

bus_notify(dev, BUS_NOTIFY_UNBIND_DRIVER);

- pm_runtime_put_sync(dev);
-
device_remove(dev);

+ pm_runtime_put_sync(dev);
+
if (dev->bus && dev->bus->dma_cleanup)
dev->bus->dma_cleanup(dev);

--
2.39.2