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Date:   Sat, 24 Apr 2021 12:00:46 +0200
From:   Johan Hovold <johan@kernel.org>
To:     Jacopo Mondi <jacopo@jmondi.org>
Cc:     Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        linuxarm@huawei.com, mauro.chehab@huawei.com,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org
Subject: Re: [PATCH 38/78] media: i2c: mt9m001: use
 pm_runtime_resume_and_get()
Message-ID: <YIPsTsEA/F+o7fhQ@hovoldconsulting.com>
References: <cover.1619191723.git.mchehab+huawei@kernel.org>
 <beddb7295807f43a190f2add6c1665b7475cb154.1619191723.git.mchehab+huawei@kernel.org>
 <20210424082454.2ciold3j3h2jw47m@uno.localdomain>
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On Sat, Apr 24, 2021 at 10:24:54AM +0200, Jacopo Mondi wrote:
> Hi Mauro,
> 
> On Sat, Apr 24, 2021 at 08:44:48AM +0200, Mauro Carvalho Chehab wrote:
> > Commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> > added pm_runtime_resume_and_get() in order to automatically handle
> > dev->power.usage_count decrement on errors.
> >
> > Use the new API, in order to cleanup the error check logic.
> >
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> 
> Thanks
> Acked-by: Jacopo Mondi <jacopo@jmondi.org>
> 
> I should re-work the error handling sequence there on top of this
> patch as right now it's not the best, that 'done' label bothers me...
> anyway, for later.
> 
> > ---
> >  drivers/media/i2c/mt9m001.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/i2c/mt9m001.c b/drivers/media/i2c/mt9m001.c
> > index 3b0ba8ed5233..57e15a291ebd 100644
> > --- a/drivers/media/i2c/mt9m001.c
> > +++ b/drivers/media/i2c/mt9m001.c
> > @@ -217,9 +217,9 @@ static int mt9m001_s_stream(struct v4l2_subdev *sd, int enable)
> >  		goto done;
> >
> >  	if (enable) {
> > -		ret = pm_runtime_get_sync(&client->dev);
> > +		ret = pm_runtime_resume_and_get(&client->dev);
> >  		if (ret < 0)
> > -			goto put_unlock;
> > +			goto unlock;
> >
> >  		ret = mt9m001_apply_selection(sd);
> >  		if (ret)
> > @@ -247,6 +247,7 @@ static int mt9m001_s_stream(struct v4l2_subdev *sd, int enable)
> >
> >  put_unlock:
> >  	pm_runtime_put(&client->dev);
> > +unlock:
> >  	mutex_unlock(&mt9m001->mutex);
> >
> >  	return ret;
> > @@ -834,7 +835,7 @@ static int mt9m001_remove(struct i2c_client *client)
> >  {
> >  	struct mt9m001 *mt9m001 = to_mt9m001(client);
> >
> > -	pm_runtime_get_sync(&client->dev);
> > +	pm_runtime_resume_and_get(&client->dev);
> >
> >  	v4l2_async_unregister_subdev(&mt9m001->subdev);
> >  	media_entity_cleanup(&mt9m001->subdev.entity);

I couldn't help looking at one more now that you got feedback on this
one.

Here you have the same problem as the one I reported earlier, in that
the usage count could end up negative on resume failure due to the later
put_noidle() call in remove().

Also note that you're adding more lines than you're removing.

I'd say this kind of mass-conversion is of questionable worth as
pm_runtime_resume_and_get() isn't necessarily an improvement (even if it
may have its use in some places).

Johan