Re: [PATCH 25/25] media: i2c: ccs-core: fix pm_runtime_get_sync() usage count

[Mauro Carvalho Chehab]

Em Wed, 5 May 2021 13:34:09 +0300
Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> escreveu:

> Hi Mauro,
> 
> Thanks for the patch.
> 
> On Wed, May 05, 2021 at 11:42:15AM +0200, Mauro Carvalho Chehab wrote:
> > The pm_runtime_get_sync() internally increments the
> > dev->power.usage_count without decrementing it, even on errors.
> > 
> > There is a bug at ccs_pm_get_init(): when this function returns
> > an error, the stream is not started, and RPM usage_count
> > should not be incremented. However, if the calls to
> > v4l2_ctrl_handler_setup() return errors, it will be kept
> > incremented.
> > 
> > At ccs_suspend() the best is to replace it by the new
> > pm_runtime_resume_and_get(), introduced by:
> > commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> > in order to properly decrement the usage counter automatically,
> > in the case of errors.
> > 
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>  
> 
> Could you add Fixes: line and Cc: stable?

Sure. See the fixes one enclosed.

> The patch that breaks this is 96e3a6b92f23a .
> 
> It would be better to fix the bug first so the patch to the stable trees
> doesn't need special handling.
> 
> > ---
> >  drivers/media/i2c/ccs/ccs-core.c | 39 ++++++++++++++++++++------------
> >  1 file changed, 24 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/media/i2c/ccs/ccs-core.c b/drivers/media/i2c/ccs/ccs-core.c
> > index b05f409014b2..04c3ab9e37b4 100644
> > --- a/drivers/media/i2c/ccs/ccs-core.c
> > +++ b/drivers/media/i2c/ccs/ccs-core.c
> > @@ -1880,21 +1880,33 @@ static int ccs_pm_get_init(struct ccs_sensor *sensor)
> >  	struct i2c_client *client = v4l2_get_subdevdata(&sensor->src->sd);
> >  	int rval;
> >  
> > +	/*
> > +	 * It can't use pm_runtime_resume_and_get() here, as the driver
> > +	 * relies at the returned value to detect if the device was already
> > +	 * active or not.
> > +	 */
> >  	rval = pm_runtime_get_sync(&client->dev);
> > -	if (rval < 0) {
> > -		pm_runtime_put_noidle(&client->dev);
> > +	if (rval < 0)
> > +		goto error;
> >  
> > -		return rval;
> > -	} else if (!rval) {
> > -		rval = v4l2_ctrl_handler_setup(&sensor->pixel_array->
> > -					       ctrl_handler);
> > -		if (rval)
> > -			return rval;
> > +	/* Device was already active, so don't set controls */
> > +	if (rval == 1)
> > +		return 0;
> >  
> > -		return v4l2_ctrl_handler_setup(&sensor->src->ctrl_handler);
> > -	}
> > +	/* Restore V4L2 controls to the suspended device */
> > +	rval = v4l2_ctrl_handler_setup(&sensor->pixel_array->ctrl_handler);
> > +	if (rval)
> > +		goto error;
> >  
> > +	rval = v4l2_ctrl_handler_setup(&sensor->src->ctrl_handler);
> > +	if (rval)
> > +		goto error;
> > +
> > +	/* Keep PM runtime usage_count incremented on success */
> >  	return 0;
> > +error:
> > +	pm_runtime_put_noidle(&client->dev);  
> 
> This needs to be pm_runtime_put() as the device has been successfully.

Ok.

> 
> > +	return rval;
> >  }
> >  
> >  static int ccs_set_stream(struct v4l2_subdev *subdev, int enable)
> > @@ -3089,12 +3101,9 @@ static int __maybe_unused ccs_suspend(struct device *dev)
> >  	bool streaming = sensor->streaming;
> >  	int rval;
> >  
> > -	rval = pm_runtime_get_sync(dev);
> > -	if (rval < 0) {
> > -		pm_runtime_put_noidle(dev);
> > -
> > +	rval = pm_runtime_resume_and_get(dev);
> > +	if (rval < 0)
> >  		return rval;
> > -	}
> >  
> >  	if (sensor->streaming)
> >  		ccs_stop_streaming(sensor);  
> 

Thanks,
Mauro

---

[PATCH] media: i2c: ccs-core: fix pm_runtime_get_sync() usage count

The pm_runtime_get_sync() internally increments the
dev->power.usage_count without decrementing it, even on errors.

There is a bug at ccs_pm_get_init(): when this function returns
an error, the stream is not started, and RPM usage_count
should not be incremented. However, if the calls to
v4l2_ctrl_handler_setup() return errors, it will be kept
incremented.

At ccs_suspend() the best is to replace it by the new
pm_runtime_resume_and_get(), introduced by:
commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
in order to properly decrement the usage counter automatically,
in the case of errors.

Fixes: 96e3a6b92f23 ("media: smiapp: Avoid maintaining power state information")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>

diff --git a/drivers/media/i2c/ccs/ccs-core.c b/drivers/media/i2c/ccs/ccs-core.c
index b05f409014b2..5ea471fefa3a 100644
--- a/drivers/media/i2c/ccs/ccs-core.c
+++ b/drivers/media/i2c/ccs/ccs-core.c
@@ -1880,21 +1880,33 @@ static int ccs_pm_get_init(struct ccs_sensor *sensor)
 	struct i2c_client *client = v4l2_get_subdevdata(&sensor->src->sd);
 	int rval;
 
+	/*
+	 * It can't use pm_runtime_resume_and_get() here, as the driver
+	 * relies at the returned value to detect if the device was already
+	 * active or not.
+	 */
 	rval = pm_runtime_get_sync(&client->dev);
-	if (rval < 0) {
-		pm_runtime_put_noidle(&client->dev);
+	if (rval < 0)
+		goto error;
 
-		return rval;
-	} else if (!rval) {
-		rval = v4l2_ctrl_handler_setup(&sensor->pixel_array->
-					       ctrl_handler);
-		if (rval)
-			return rval;
+	/* Device was already active, so don't set controls */
+	if (rval == 1)
+		return 0;
 
-		return v4l2_ctrl_handler_setup(&sensor->src->ctrl_handler);
-	}
+	/* Restore V4L2 controls to the suspended device */
+	rval = v4l2_ctrl_handler_setup(&sensor->pixel_array->ctrl_handler);
+	if (rval)
+		goto error;
 
+	rval = v4l2_ctrl_handler_setup(&sensor->src->ctrl_handler);
+	if (rval)
+		goto error;
+
+	/* Keep PM runtime usage_count incremented on success */
 	return 0;
+error:
+	pm_runtime_put(&client->dev);
+	return rval;
 }
 
 static int ccs_set_stream(struct v4l2_subdev *subdev, int enable)