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    SubjectRe: [PATCH 17/78] staging: media: vde: use pm_runtime_resume_and_get()
    Hi Dmitry,

    Em Sat, 24 Apr 2021 10:35:22 +0300
    Dmitry Osipenko <digetx@gmail.com> escreveu:

    > 24.04.2021 09:44, Mauro Carvalho Chehab пишет:
    > > 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/staging/media/tegra-vde/vde.c | 16 ++++++++++------
    > > 1 file changed, 10 insertions(+), 6 deletions(-)
    > >
    > > diff --git a/drivers/staging/media/tegra-vde/vde.c b/drivers/staging/media/tegra-vde/vde.c
    > > index 28845b5bafaf..8936f140a246 100644
    > > --- a/drivers/staging/media/tegra-vde/vde.c
    > > +++ b/drivers/staging/media/tegra-vde/vde.c
    > > @@ -775,9 +775,9 @@ static int tegra_vde_ioctl_decode_h264(struct tegra_vde *vde,
    > > if (ret)
    > > goto release_dpb_frames;
    > >
    > > - ret = pm_runtime_get_sync(dev);
    > > + ret = pm_runtime_resume_and_get(dev);
    > > if (ret < 0)
    > > - goto put_runtime_pm;
    > > + goto unlock;
    > >
    > > /*
    > > * We rely on the VDE registers reset value, otherwise VDE
    > > @@ -843,6 +843,8 @@ static int tegra_vde_ioctl_decode_h264(struct tegra_vde *vde,
    > > put_runtime_pm:
    > > pm_runtime_mark_last_busy(dev);
    > > pm_runtime_put_autosuspend(dev);
    > > +
    > > +unlock:
    > > mutex_unlock(&vde->lock);
    > >
    > > release_dpb_frames:
    > > @@ -1069,8 +1071,8 @@ static int tegra_vde_probe(struct platform_device *pdev)
    > > * power-cycle it in order to put hardware into a predictable lower
    > > * power state.
    > > */
    > > - pm_runtime_get_sync(dev);
    > > - pm_runtime_put(dev);
    > > + if (pm_runtime_resume_and_get(dev) >= 0)
    > > + pm_runtime_put(dev);
    > >
    > > return 0;
    > >
    > > @@ -1088,8 +1090,9 @@ static int tegra_vde_remove(struct platform_device *pdev)
    > > {
    > > struct tegra_vde *vde = platform_get_drvdata(pdev);
    > > struct device *dev = &pdev->dev;
    > > + int ret;
    > >
    > > - pm_runtime_get_sync(dev);
    > > + ret = pm_runtime_resume_and_get(dev);
    > > pm_runtime_dont_use_autosuspend(dev);
    > > pm_runtime_disable(dev);
    > >
    > > @@ -1097,7 +1100,8 @@ static int tegra_vde_remove(struct platform_device *pdev)
    > > * Balance RPM state, the VDE power domain is left ON and hardware
    > > * is clock-gated. It's safe to reboot machine now.
    > > */
    > > - pm_runtime_put_noidle(dev);
    > > + if (ret >= 0)
    > > + pm_runtime_put_noidle(dev);
    > > clk_disable_unprepare(vde->clk);
    > >
    > > misc_deregister(&vde->miscdev);
    > >
    >
    > Hello Mauro,
    >
    > Thank you very much for the patch. It looks to me that the original
    > variant was a bit simpler, this patch adds more code lines without
    > changing the previous behaviour. Or am I missing something?

    While on several places the newer code is simpler, the end goal here is
    to replace all occurrences of pm_runtime_get_sync() from the media
    subsystem, due to the number of problems we're having with this:

    1. despite its name, this is actually a PM runtime resume call,
    but some developers didn't seem to realize that, as I got this
    pattern on some drivers:

    pm_runtime_get_sync(&client->dev);
    pm_runtime_disable(&client->dev);
    pm_runtime_set_suspended(&client->dev);
    pm_runtime_put_noidle(&client->dev);

    It makes no sense to resume PM just to suspend it again ;-)

    The name of the new variant is a lot clearer:
    pm_runtime_resume_and_get()

    2. Usual *_get() methods only increment their use count on success,
    but pm_runtime_get_sync() increments it unconditionally. Due to
    that, several drivers were mistakenly not calling
    pm_runtime_put_noidle() when it fails;

    3. Consistency: we did similar changes subsystem wide with
    for instance strlcpy() and strcpy() that got replaced by
    strscpy(). Having all drivers using the same known-to-be-safe
    methods is a good thing;

    4. Prevent newer drivers to copy-and-paste a code that it would
    be easier to break if they don't truly understand what's behind
    the scenes.

    Thanks,
    Mauro

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