Hi Dmitry,
Em Sat, 24 Apr 2021 10:35:22 +0300
Dmitry Osipenko <dig...@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+hua...@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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