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

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Date:   Tue, 16 May 2023 16:22:58 +0300
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>
Cc:     laurent.pinchart@...asonboard.com, kernel@...i.sm,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        mchehab@...nel.org
Subject: Re: [PATCH v2] media: hi846: fix usage of pm_runtime_get_if_in_use()

Hi Martin,

On Tue, Apr 25, 2023 at 11:47:47AM +0200, Martin Kepplinger wrote:
> 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.

I guess it's appropriate to add:

Fixes: e8c0882685f9 ("media: i2c: add driver for the SK Hynix Hi-846 8M pixel camera")

-- 
Sakari Ailus