linux-kernel - Re: [PATCH 58/78] media: exynos-gsc: use pm_runtime_resume_and

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Message-ID: <20210427114235.45a7b2a4@coco.lan>
Date:   Tue, 27 Apr 2021 11:42:35 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc:     linuxarm@...wei.com, mauro.chehab@...wei.com,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH 58/78] media: exynos-gsc: use
 pm_runtime_resume_and_get()

Em Tue, 27 Apr 2021 11:30:55 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> escreveu:

> Em Tue, 27 Apr 2021 10:18:12 +0200
> Sylwester Nawrocki <s.nawrocki@...sung.com> escreveu:
> 
> > On 24.04.2021 08:45, 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/platform/exynos-gsc/gsc-core.c | 3 +--
> > >  drivers/media/platform/exynos-gsc/gsc-m2m.c  | 2 +-
> > >  2 files changed, 2 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/media/platform/exynos-gsc/gsc-core.c b/drivers/media/platform/exynos-gsc/gsc-core.c
> > > index 9f41c2e7097a..9d5841194f6b 100644
> > > --- a/drivers/media/platform/exynos-gsc/gsc-core.c
> > > +++ b/drivers/media/platform/exynos-gsc/gsc-core.c
> > > @@ -1210,7 +1210,7 @@ static int gsc_remove(struct platform_device *pdev)
> > >  	struct gsc_dev *gsc = platform_get_drvdata(pdev);
> > >  	int i;
> > >  
> > > -	pm_runtime_get_sync(&pdev->dev);
> > > +	pm_runtime_resume_and_get(&pdev->dev);
> > >  
> > >  	gsc_unregister_m2m_device(gsc);
> > >  	v4l2_device_unregister(&gsc->v4l2_dev);
> > > @@ -1219,7 +1219,6 @@ static int gsc_remove(struct platform_device *pdev)
> > >  	for (i = 0; i < gsc->num_clocks; i++)
> > >  		clk_disable_unprepare(gsc->clock[i]);
> > >  
> > > -	pm_runtime_put_noidle(&pdev->dev);    
> > 
> > If we do this then the device usage count will not get decremented
> > after the pm_runtime_resume_and_get() call above and after driver
> > unload/load cycle it will not be possible to suspend the device.
> > I wouldn't be changing anything in gsc_remove(), pm_runtime_get_sync()
> > works better in that case.  
> 
> Good point.
> 
> Actually, I don't see any reason why to call a PM resume
> function - either being pm_runtime_get_sync() or
> pm_runtime_resume_and_get().
> 
> The code there could simply be:
> 
>     static int gsc_remove(struct platform_device *pdev)
>     {
>         struct gsc_dev *gsc = platform_get_drvdata(pdev);
>         int i;
> 
>         gsc_unregister_m2m_device(gsc);
>         v4l2_device_unregister(&gsc->v4l2_dev);
> 
>         vb2_dma_contig_clear_max_seg_size(&pdev->dev);
>         for (i = 0; i < gsc->num_clocks; i++)
>                 clk_disable_unprepare(gsc->clock[i]);
> 
>         pm_runtime_disable(&pdev->dev);
> 
>         dev_dbg(&pdev->dev, "%s driver unloaded\n", pdev->name);
>         return 0;
>     }
> 
> Eventually also adding:
> 	pm_runtime_suspended(&pdev->dev);

In time: I actually meant:

	pm_runtime_set_suspended(&pdev->dev);

but after double-checking the PM runtime code, it sounds to me that
just calling pm_runtime_disable() would be enough. Not 100% sure
here. Btw, some media drivers call it after pm_runtime_disable(),
while others don't do.

Thanks,
Mauro