linux-kernel - [PATCH v2] media: hi846: fix usage of pm_runtime_get_if_in

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Message-Id: <20230425094747.2769693-1-martin.kepplinger@puri.sm>
Date:   Tue, 25 Apr 2023 11:47:47 +0200
From:   Martin Kepplinger <martin.kepplinger@...i.sm>
To:     laurent.pinchart@...asonboard.com
Cc:     kernel@...i.sm, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, martin.kepplinger@...i.sm,
        mchehab@...nel.org, sakari.ailus@....fi
Subject: [PATCH v2] media: hi846: fix usage of pm_runtime_get_if_in_use()

pm_runtime_get_if_in_use() does not only return nonzero values when
the device is in use, it can return a negative errno too.

And especially during resuming from system suspend, when runtime pm
is not yet up again, -EAGAIN is being returned, so the subsequent
pm_runtime_put() call results in a refcount underflow.

Fix system-resume by handling -EAGAIN of pm_runtime_get_if_in_use().

Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
---

revision history
----------------
v2 (thank you Sakari and Laurent):
* drop the other patch (the streaming-state in suspend/resume needs to
  be solved differently).
* Sakari pointed out that many drivers are affected by this and that
  runtime-pm might need changes instead. I think this patch doesn't hurt
  and could serve as a reminder to do so.

v1: initial submission:
https://lore.kernel.org/linux-media/20230405092904.1129395-1-martin.kepplinger@puri.sm/

 drivers/media/i2c/hi846.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/hi846.c b/drivers/media/i2c/hi846.c
index 306dc35e925f..f8709cdf28b3 100644
--- a/drivers/media/i2c/hi846.c
+++ b/drivers/media/i2c/hi846.c
@@ -1353,7 +1353,8 @@ static int hi846_set_ctrl(struct v4l2_ctrl *ctrl)
 					 exposure_max);
 	}
 
-	if (!pm_runtime_get_if_in_use(&client->dev))
+	ret = pm_runtime_get_if_in_use(&client->dev);
+	if (!ret || ret == -EAGAIN)
 		return 0;
 
 	switch (ctrl->id) {
-- 
2.30.2