linux-kernel - Re: Re: [PATCH] media: imx: imx7-mipi-csis: Fix runtime PM imbalance in mipi_csis_s

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Date:   Fri, 9 Apr 2021 15:59:53 +0800 (GMT+08:00)
From:   dinghao.liu@....edu.cn
To:     "Rui Miguel Silva" <rmfrfs@...il.com>
Cc:     kjlu@....edu, "Steve Longerbeam" <slongerbeam@...il.com>,
        "Philipp Zabel" <p.zabel@...gutronix.de>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Shawn Guo" <shawnguo@...nel.org>,
        "Sascha Hauer" <s.hauer@...gutronix.de>,
        "Pengutronix Kernel Team" <kernel@...gutronix.de>,
        "Fabio Estevam" <festevam@...il.com>,
        "NXP Linux Team" <linux-imx@....com>, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH] media: imx: imx7-mipi-csis: Fix runtime PM
 imbalance in mipi_csis_s_stream

> Hi Liu,
> Thanks for your patch.
> 
> On Thu, Apr 08, 2021 at 05:08:27PM +0800, Dinghao Liu wrote:
> > When v4l2_subdev_call() fails, a pairing PM usage counter
> > decrement is needed to keep the counter balanced. It's the
> > same for the following error paths in case 'enable' is on.
> > 
> > Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> > ---
> >  drivers/staging/media/imx/imx7-mipi-csis.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/staging/media/imx/imx7-mipi-csis.c b/drivers/staging/media/imx/imx7-mipi-csis.c
> > index a01a7364b4b9..2a3fff231a40 100644
> > --- a/drivers/staging/media/imx/imx7-mipi-csis.c
> > +++ b/drivers/staging/media/imx/imx7-mipi-csis.c
> > @@ -627,21 +627,26 @@ static int mipi_csis_s_stream(struct v4l2_subdev *mipi_sd, int enable)
> >  			return ret;
> >  		}
> >  		ret = v4l2_subdev_call(state->src_sd, core, s_power, 1);
> > -		if (ret < 0)
> > +		if (ret < 0) {
> > +			pm_runtime_put_noidle(&state->pdev->dev);
> 
> I think here we should go completely pm_runtime_put to call the
> mipi_csis_pm_suspend down the line, right?
> 
> >  			return ret;
> > +		}
> >  	}
> >  
> >  	mutex_lock(&state->lock);
> >  	if (enable) {
> >  		if (state->flags & ST_SUSPENDED) {
> >  			ret = -EBUSY;
> > +			pm_runtime_put_noidle(&state->pdev->dev);
> 
> since we are in ST_SUSPENDED state, for sure the pm counter was
> already 0.
> 
> >  			goto unlock;
> >  		}
> >  
> >  		mipi_csis_start_stream(state);
> >  		ret = v4l2_subdev_call(state->src_sd, video, s_stream, 1);
> > -		if (ret < 0)
> > +		if (ret < 0) {
> > +			pm_runtime_put_noidle(&state->pdev->dev);
> 
> here also we need the pm_runtime_put, maybe just changing the unlock
> tag bellow from:
>     if (!enable)
>         pm_runtime_put(&state->pdev->dev);
> 
> to 
>     if (!enable || (ret < 0))
>         pm_runtime_put(&state->pdev->dev);
> 
> will not hurt the first case and will complete the suspend routine
> afterward in the second case.
> 

This is much clearer, thanks! I will fix this and send a new patch soon.

Regards,
Dinghao