linux-kernel - Re: [PATCH 02/25] staging: media: imx7-mipi-csis: fix pm_runtime_get

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Date:   Wed, 05 May 2021 14:56:40 +0100
From:   "Rui Miguel Silva" <rmfrfs@...il.com>
To:     "Jonathan Cameron" <Jonathan.Cameron@...wei.com>,
        "Mauro Carvalho Chehab" <mchehab+huawei@...nel.org>
Cc:     <linuxarm@...wei.com>, <mauro.chehab@...wei.com>,
        "Fabio Estevam" <festevam@...il.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        "NXP Linux Team" <linux-imx@....com>,
        "Pengutronix Kernel Team" <kernel@...gutronix.de>,
        "Philipp Zabel" <p.zabel@...gutronix.de>,
        "Sascha Hauer" <s.hauer@...gutronix.de>,
        "Shawn Guo" <shawnguo@...nel.org>,
        "Steve Longerbeam" <slongerbeam@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <linux-staging@...ts.linux.dev>
Subject: Re: [PATCH 02/25] staging: media: imx7-mipi-csis: fix
 pm_runtime_get_sync() usage count

Hi,
On Wed May 5, 2021 at 12:06 PM WEST, Jonathan Cameron wrote:

> On Wed, 5 May 2021 11:41:52 +0200
> Mauro Carvalho Chehab <mchehab+huawei@...nel.org> wrote:
>
> > The pm_runtime_get_sync() internally increments the
> > dev->power.usage_count without decrementing it, even on errors.
> > 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, avoiding
> > a potential PM usage counter leak.
> > 
> > Acked-by: Rui Miguel Silva <rmfrfs@...il.com>
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
>
> Not a fix as far as I can see, just a cleanup - so perhaps not this set?

yes, the original changelog of this patch, that I acked,  made it
clear it was a cleanup:

"
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.
"

This one above is new, but I saw Mauro is going change it.

------
Cheers,
     Rui

>
> Jonathan
>
>
> > ---
> >  drivers/staging/media/imx/imx7-mipi-csis.c | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/staging/media/imx/imx7-mipi-csis.c b/drivers/staging/media/imx/imx7-mipi-csis.c
> > index 025fdc488bd6..1dc680d94a46 100644
> > --- a/drivers/staging/media/imx/imx7-mipi-csis.c
> > +++ b/drivers/staging/media/imx/imx7-mipi-csis.c
> > @@ -695,11 +695,10 @@ static int mipi_csis_s_stream(struct v4l2_subdev *mipi_sd, int enable)
> >  
> >  		mipi_csis_clear_counters(state);
> >  
> > -		ret = pm_runtime_get_sync(&state->pdev->dev);
> > -		if (ret < 0) {
> > -			pm_runtime_put_noidle(&state->pdev->dev);
> > +		ret = pm_runtime_resume_and_get(&state->pdev->dev);
> > +		if (ret < 0)
> >  			return ret;
> > -		}
> > +
> >  		ret = v4l2_subdev_call(state->src_sd, core, s_power, 1);
> >  		if (ret < 0 && ret != -ENOIOCTLCMD)
> >  			goto done;