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

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Message-ID: <20210427113055.745d0560@coco.lan>
Date:   Tue, 27 Apr 2021 11:30:55 +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 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);

just after pm_runtime_disable().

Regards,
Mauro