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    SubjectRe: [PATCH 58/78] media: exynos-gsc: use pm_runtime_resume_and_get()
    Em Wed, 28 Apr 2021 09:13:02 +0200
    Mauro Carvalho Chehab <mchehab+huawei@kernel.org> escreveu:

    > Em Tue, 27 Apr 2021 13:50:44 +0200
    > Sylwester Nawrocki <s.nawrocki@samsung.com> escreveu:
    >
    > > On 27.04.2021 11:42, Mauro Carvalho Chehab wrote:
    > > > Em Tue, 27 Apr 2021 11:30:55 +0200
    > > > Mauro Carvalho Chehab <mchehab+huawei@kernel.org> escreveu:
    > > >
    > > >> Em Tue, 27 Apr 2021 10:18:12 +0200
    > > >> Sylwester Nawrocki <s.nawrocki@samsung.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@kernel.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.
    > >
    > > I think if the device is brought into suspended state (e.g. by
    > > disabling clocks as above) the pm_runtime_set_suspended() call
    > > should be there. IOW a following sequence:
    > >
    > > pm_runtime_disable(dev);
    > > if (!pm_runtime_status_suspended(dev))
    > > /* put device into suspended state (disable clocks,
    > > voltage regulators, assert GPIOs, etc. */
    > > pm_runtime_set_suspended(dev);
    >
    > Not sure if this would work, as the clock framework would try
    > to do things like calling clk_pm_runtime_put().
    >
    > Perhaps an alternative would be to just return an error if it
    > can't resume PM runtime, e. g.:
    >
    > diff --git a/drivers/media/platform/exynos-gsc/gsc-core.c b/drivers/media/platform/exynos-gsc/gsc-core.c
    > index 9f41c2e7097a..d47d02c75484 100644
    > --- a/drivers/media/platform/exynos-gsc/gsc-core.c
    > +++ b/drivers/media/platform/exynos-gsc/gsc-core.c
    > @@ -1208,9 +1208,11 @@ static int gsc_probe(struct platform_device *pdev)
    > static int gsc_remove(struct platform_device *pdev)
    > {
    > struct gsc_dev *gsc = platform_get_drvdata(pdev);
    > - int i;
    > + int ret, i;
    >
    > - pm_runtime_get_sync(&pdev->dev);
    > + ret = pm_runtime_resume_and_get(&pdev->dev);
    > + if (ret < 0)
    > + return ret;

    Nah, forget about that. Despite the platform driver having a return code,
    support for it bogus:


    static int platform_remove(struct device *_dev)
    {
    struct platform_driver *drv = to_platform_driver(_dev->driver);
    struct platform_device *dev = to_platform_device(_dev);

    if (drv->remove) {
    int ret = drv->remove(dev);

    if (ret)
    dev_warn(_dev, "remove callback returned a non-zero value. This will be ignored.\n");
    }
    dev_pm_domain_detach(_dev, true);

    return 0;
    }

    Thanks,
    Mauro

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