linux-kernel - Re: [PATCH 25/78] media: i2c: ccs-core: use pm_runtime_resume_and

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Date:   Mon, 26 Apr 2021 16:16:59 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linuxarm@...wei.com, mauro.chehab@...wei.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH 25/78] media: i2c: ccs-core: use
 pm_runtime_resume_and_get()

Em Mon, 26 Apr 2021 17:09:00 +0300
Sakari Ailus <sakari.ailus@...ux.intel.com> escreveu:

> Hi Mauro,
> 
> On Mon, Apr 26, 2021 at 04:01:51PM +0200, Mauro Carvalho Chehab wrote:
> > Em Sun, 25 Apr 2021 21:55:25 +0300
> > Sakari Ailus <sakari.ailus@...ux.intel.com> escreveu:
> >   
> > > Hi Mauro,
> > > 
> > > Thanks for the patch.
> > > 
> > > On Sat, Apr 24, 2021 at 08:44:35AM +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@...nel.org>
> > > > ---
> > > >  drivers/media/i2c/ccs/ccs-core.c | 11 +++++------
> > > >  1 file changed, 5 insertions(+), 6 deletions(-)
> > > > 
> > > > diff --git a/drivers/media/i2c/ccs/ccs-core.c b/drivers/media/i2c/ccs/ccs-core.c
> > > > index 9dc3f45da3dc..1441ddcc9b35 100644
> > > > --- a/drivers/media/i2c/ccs/ccs-core.c
> > > > +++ b/drivers/media/i2c/ccs/ccs-core.c
> > > > @@ -1880,12 +1880,11 @@ static int ccs_pm_get_init(struct ccs_sensor *sensor)
> > > >  	struct i2c_client *client = v4l2_get_subdevdata(&sensor->src->sd);
> > > >  	int rval;
> > > >  
> > > > -	rval = pm_runtime_get_sync(&client->dev);
> > > > -	if (rval < 0) {
> > > > -		pm_runtime_put_noidle(&client->dev);
> > > > -
> > > > +	rval = pm_runtime_resume_and_get(&client->dev);
> > > > +	if (rval < 0)
> > > >  		return rval;
> > > > -	} else if (!rval) {
> > > > +
> > > > +	if (!rval) {
> > > >  		rval = v4l2_ctrl_handler_setup(&sensor->pixel_array->
> > > >  					       ctrl_handler);
> > > >  		if (rval)
> > > > @@ -3089,7 +3088,7 @@ static int __maybe_unused ccs_suspend(struct device *dev)
> > > >  	bool streaming = sensor->streaming;
> > > >  	int rval;
> > > >  
> > > > -	rval = pm_runtime_get_sync(dev);
> > > > +	rval = pm_runtime_resume_and_get(dev);
> > > >  	if (rval < 0) {
> > > >  		pm_runtime_put_noidle(dev);    
> > > 
> > > You'll need to drop pm_runtime_put_noidle() here.  
> > 
> > OK!
> > 
> > ---
> > 
> > On a non-related issue at the same code, after the change, the
> > suspend function will be:
> > 
> >   static int __maybe_unused ccs_suspend(struct device *dev)
> >   {
> >         struct i2c_client *client = to_i2c_client(dev);
> >         struct v4l2_subdev *subdev = i2c_get_clientdata(client);
> >         struct ccs_sensor *sensor = to_ccs_sensor(subdev);
> >         bool streaming = sensor->streaming;
> >         int rval;
> > 
> >         rval = pm_runtime_resume_and_get(dev);
> >         if (rval < 0) 
> >                 return -EAGAIN;
> > 
> >         if (sensor->streaming)
> >                 ccs_stop_streaming(sensor);
> > 
> >         /* save state for resume */
> >         sensor->streaming = streaming;
> > 
> >         return 0;
> >   }
> > 
> > Not sure if "return -EAGAIN" is the right thing here. I mean,
> > the PM runtime core has two error conditions that are independent
> > on whatever the PM callback would be doing[1]:
> > 
> > 	        if (dev->power.runtime_error)
> >                 retval = -EINVAL;
> >         else if (dev->power.disable_depth > 0)
> >                 retval = -EACCES;
> > 
> > It would be very unlikely that trying to suspend again would solve
> > those conditions.
> > 
> > So, I guess that the right thing to do is to change the code
> > to do, instead:
> > 
> >   static int __maybe_unused ccs_suspend(struct device *dev)
> >   {
> >         struct i2c_client *client = to_i2c_client(dev);
> >         struct v4l2_subdev *subdev = i2c_get_clientdata(client);
> >         struct ccs_sensor *sensor = to_ccs_sensor(subdev);
> >         bool streaming = sensor->streaming;
> >         int rval;
> > 
> >         rval = pm_runtime_resume_and_get(dev);
> >         if (rval < 0) 
> >                 return rval;
> > 	...
> >   }
> > 
> > 
> > [1] see rpm_resume() code at drivers/base/power/runtime.c.  
> 
> Yeah, I agree. This code is one of the older parts the driver.
> 
> Please add:
> 
> Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> 
> The same goes for the other sensor driver patches in the set you cc'd me,
> i.e. patches 12, 15, 26, 28,32, 40, 45, 51, 53 and 55.

It probably makes sense to address the suspend/resume -EAGAIN
return code on a separate patch series, before this one, as:

1. this is unrelated to this change;
2. it is something that should be c/c to fixes. So, having it
   before this series makes easier to apply there.

Thanks,
Mauro