linux-kernel - Re: Re: [PATCH] media: coda: Fix runtime PM imbalance in coda

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Date:   Mon, 25 May 2020 20:52:49 +0800 (GMT+08:00)
From:   dinghao.liu@....edu.cn
To:     "Philipp Zabel" <pza@...gutronix.de>
Cc:     kjlu@....edu, "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH] media: coda: Fix runtime PM imbalance in coda_probe

> Hi Dinghao,
> 
> thank you for the patch! The first part is fine, but I think the second
> part is not necessary, see below:
> 
> On Sat, May 23, 2020 at 06:03:32PM +0800, Dinghao Liu wrote:
> > When coda_firmware_request() returns an error code,
> > a pairing runtime PM usage counter decrement is needed
> > to keep the counter balanced.
> > 
> > Also, the caller expects coda_probe() to increase PM
> > usage counter, there should be a refcount decrement
> > in coda_remove() to keep the counter balanced.
> 
> coda_probe() increments the usage counter only until coda_fw_callback()
> decrements it again. Where is the imbalance?
> 

You are right, I missed coda_firmware_request() before and 
thank you for your correction! I will fix this in the next
edition of patch.

Regards,
Dinghao

> > Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> > ---
> >  drivers/media/platform/coda/coda-common.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/media/platform/coda/coda-common.c b/drivers/media/platform/coda/coda-common.c
> > index d0d093dd8f7c..550e9a1266da 100644
> > --- a/drivers/media/platform/coda/coda-common.c
> > +++ b/drivers/media/platform/coda/coda-common.c
> > @@ -3119,6 +3119,8 @@ static int coda_probe(struct platform_device *pdev)
> >  	return 0;
> >  
> >  err_alloc_workqueue:
> > +	pm_runtime_disable(&pdev->dev);
> > +	pm_runtime_put_noidle(&pdev->dev);
> 
> These seem right, they balance out the pm_runtime_enable()
> and pm_runtime_get_noresume() right before the error.
> 
> >  	destroy_workqueue(dev->workqueue);
> >  err_v4l2_register:
> >  	v4l2_device_unregister(&dev->v4l2_dev);
> > @@ -3136,6 +3138,7 @@ static int coda_remove(struct platform_device *pdev)
> >  	}
> >  	if (dev->m2m_dev)
> >  		v4l2_m2m_release(dev->m2m_dev);
> > +	pm_runtime_put_noidle(&pdev->dev);
> 
> I think this is incorrect. There is one pm_runtime_get_noresume() in
> coda_probe(), and one pm_runtime_put_sync() in coda_fw_callback().
> By the time coda_remove() is called, balance is already restored.
> 
> regards
> Philipp