linux-kernel - Re: [PATCH v2 1/6] PM: core: Remove DEFINE_UNIVERSAL_DEV_PM

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Message-ID: <CAPDyKFpPOsoxBbamJWoAso_8cEb--Y1i4zDAnnTQ00EkSySVLQ@mail.gmail.com>
Date:   Fri, 7 Jan 2022 17:40:57 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Len Brown <len.brown@...el.com>,
        Pavel Machek <pavel@....cz>, list@...ndingux.net,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-mmc@...r.kernel.org,
        linux-pm@...r.kernel.org,
        Jonathan Cameron <jonathan.cameron@...wei.com>
Subject: Re: [PATCH v2 1/6] PM: core: Remove DEFINE_UNIVERSAL_DEV_PM_OPS() macro

On Fri, 7 Jan 2022 at 17:37, Paul Cercueil <paul@...pouillou.net> wrote:
>
> Hi Ulf,
>
> Le ven., janv. 7 2022 at 17:26:07 +0100, Ulf Hansson
> <ulf.hansson@...aro.org> a écrit :
> > On Wed, 5 Jan 2022 at 19:29, Paul Cercueil <paul@...pouillou.net>
> > wrote:
> >>
> >>  The deprecated UNIVERSAL_DEV_PM_OPS() macro uses the provided
> >> callbacks
> >>  for both runtime PM and system sleep, which is very likely to be a
> >>  mistake, as a system sleep can be triggered while a given device is
> >>  already PM-suspended, which would cause the suspend callback to be
> >>  called twice.
> >>
> >>  The amount of users of UNIVERSAL_DEV_PM_OPS() is also tiny (16
> >>  occurences) compared to the number of places where
> >>  SET_SYSTEM_SLEEP_PM_OPS() is used with pm_runtime_force_suspend()
> >> and
> >>  pm_runtime_force_resume(), which makes me think that none of these
> >> cases
> >>  are actually valid.
> >>
> >>  As this macro is currently unused, remove it before someone starts
> >> to
> >>  use it in yet another invalid case.
> >
> > I assume you refer to DEFINE_UNIVERSAL_DEV_PM_OPS here. Can you
> > perhaps make that more clear?
>
> I can.
>
> >>
> >>  Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> >>  Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> >>  ---
> >>
> >>  Notes:
> >>      v2: No change
> >>
> >>   include/linux/pm.h | 19 ++++++-------------
> >>   1 file changed, 6 insertions(+), 13 deletions(-)
> >>
> >>  diff --git a/include/linux/pm.h b/include/linux/pm.h
> >>  index e1e9402180b9..31bbaafb06d2 100644
> >>  --- a/include/linux/pm.h
> >>  +++ b/include/linux/pm.h
> >>  @@ -366,6 +366,12 @@ static const struct dev_pm_ops name = { \
> >>          SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> >>   }
> >>
> >>  +/* Deprecated. Use DEFINE_SIMPLE_DEV_PM_OPS() instead. */
> >>  +#define SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
> >>  +const struct dev_pm_ops __maybe_unused name = { \
> >>  +       SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> >>  +}
> >>  +
> >>   /*
> >>    * Use this for defining a set of PM operations to be used in all
> >> situations
> >>    * (system suspend, hibernation or runtime PM).
> >>  @@ -379,19 +385,6 @@ static const struct dev_pm_ops name = { \
> >>    * .resume_early(), to the same routines as .runtime_suspend() and
> >>    * .runtime_resume(), respectively (and analogously for
> >> hibernation).
> >>    */
> >>  -#define DEFINE_UNIVERSAL_DEV_PM_OPS(name, suspend_fn, resume_fn,
> >> idle_fn) \
> >>  -static const struct dev_pm_ops name = { \
> >>  -       SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> >>  -       RUNTIME_PM_OPS(suspend_fn, resume_fn, idle_fn) \
> >>  -}
> >>  -
> >>  -/* Deprecated. Use DEFINE_SIMPLE_DEV_PM_OPS() instead. */
> >>  -#define SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
> >>  -const struct dev_pm_ops __maybe_unused name = { \
> >>  -       SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> >>  -}
> >>  -
> >>  -/* Deprecated. Use DEFINE_UNIVERSAL_DEV_PM_OPS() instead. */
> >
> > Shouldn't this macro be deprecated any more?
>
> I can only deprecate it if there is an alternative for it. The
> alternative is DEFINE_RUNTIME_DEV_PM_OPS() which is added in patch 4/6.

I don't think we need an immediate alternative to leave it deprecated, do we?

My point is, a user can still combine the macros in a way so that it
doesn't need to use the UNIVERSAL_DEV_PM_OPS.

>
> Cheers,
> -Paul
>
> >>   #define UNIVERSAL_DEV_PM_OPS(name, suspend_fn, resume_fn, idle_fn)
> >> \
> >>   const struct dev_pm_ops __maybe_unused name = { \
> >>          SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
> >>  --

Kind regards
Uffe