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

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Date:   Tue, 27 Apr 2021 09:02:58 +0200
From:   Mauro Carvalho Chehab <mchehab@...nel.org>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linuxarm@...wei.com, mauro.chehab@...wei.com,
        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()

Hi Sakari,

Em Mon, 26 Apr 2021 19:32:23 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> escreveu:

> Em Mon, 26 Apr 2021 17:29:02 +0300
> Sakari Ailus <sakari.ailus@...ux.intel.com> escreveu:
> 
> > On Mon, Apr 26, 2021 at 04:16:59PM +0200, Mauro Carvalho Chehab wrote:  
> > > 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:
> > > > >       
... 
> > > > > 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.    
> > 
> > Sounds good to me. If you can submit a patch, please add my ack. :-)  
> 
> Sure. I'll work on such patch series.

I checked the files affected by those patches:
12, 15, 26, 28,32, 40, 45, 51, 53 and 55, e.g.:


	drivers/staging/media/atomisp/pci/atomisp_fops.c
	drivers/staging/media/ipu3/ipu3.c
	drivers/media/i2c/dw9714.c
	drivers/media/i2c/dw9807-vcm.c
	drivers/media/i2c/imx258.c
	drivers/media/i2c/ov13858.c
	drivers/media/i2c/ov8865.c
	drivers/media/i2c/tvp5150.c
	drivers/media/pci/intel/ipu3/ipu3-cio2-main.c

I also double-checked the I2C drivers that use SET_SYSTEM_SLEEP_PM_OPS().
None of them are calling pm_runtime_* at suspend time, except for the
ccs-core.

So, I ended writing just a patch for ccs-core, to be applied
before this /78 series.

Thanks,
Mauro