linux-kernel - Re: [PATCH v2 04/10] pinctrl: intel: Switch to use DEFINE_NOIRQ_DEV_PM

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Date:   Tue, 18 Jul 2023 15:57:00 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Balsam CHIHI <bchihi@...libre.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-pm@...r.kernel.org, Andy Shevchenko <andy@...nel.org>,
        Sean Wang <sean.wang@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v2 04/10] pinctrl: intel: Switch to use
 DEFINE_NOIRQ_DEV_PM_OPS() helper

On Mon, Jul 17, 2023 at 10:56 PM Paul Cercueil <paul@...pouillou.net> wrote:
> Le lundi 17 juillet 2023 à 22:33 +0300, Andy Shevchenko a écrit :
> > On Mon, Jul 17, 2023 at 10:02 PM Paul Cercueil <paul@...pouillou.net>
> > wrote:
> > > Le lundi 17 juillet 2023 à 20:28 +0300, Andy Shevchenko a écrit :

...

> > > So the correct way to update this driver would be to have a
> > > conditionally-exported dev_pm_ops structure:
> > >
> > > EXPORT_GPL_DEV_PM_OPS(intel_pinctrl_pm_ops) = {
> > >     NOIRQ_SYSTEM_SLEEP_PM_OPS(intel_pinctrl_suspend_noirq,
> > > intel_pinctrl_resume_noirq),
> > > };
> >
> > This looks ugly. I didn't know that EXPORT*PM_OPS designed that way,
> > but it seems pm.h in such case needs EXPORT for NOIRQ case as well.
>
> It's designed so that when CONFIG_PM is disabled, the dev_pm_ops is
> garbage-collected along with all its callbacks.
>
> I know it looks ugly, but we already have 4 variants (regular,
> namespace, GPL, namespace + GPL), if we start to add macros for
> specific use-cases then it will become bloated really quick.

Maybe macros can be replaced / changed to make it scale?

> And the "bloat" I'm trying to avoid here is the extreme expansion of
> the API which makes it hard for people not familiar to the code to
> understand what should be used and how.

So far, based on the rest of the messages in the thread the
EXPORT*PM_OPS() have the following issues:
1) do not scale (for variants with different scope we need new set of macros);
2) do not cover cases with pm_sleep_ptr();
3) export symbols in case when it's not needed.

Am I right?

> > > Then your two callbacks can be "static" and without #ifdef guards.
> > >
> > > The resulting "intel_pinctrl_pm_ops" can be marked as "extern" in
> > > the
> > > pinctrl-intel.h without any guards, as long as it is only
> > > referenced
> > > with the pm_ptr() macro.
> >
> > I'm not sure I got this. Currently drivers do not have any guards.
> > Moreover, the correct one for noirq is pm_sleep_ptr(), isn't it?
>
> The EXPORT_*_DEV_PM_OPS() macros do export the "dev_pm_ops"
> conditionally depending on CONFIG_PM. We could add variants that export
> it conditionally depending on CONFIG_PM_SLEEP, but we're back at the
> problem of adding bloat.

Exactly.

> You could use pm_sleep_ptr() indeed, with the existing macros, with the
> drawback that in the case where CONFIG_PM && !CONFIG_PM_SLEEP, the
> dev_pm_ops + callbacks are compiled in but never referenced.

And exactly.

I don't think they are ready to use (in the current form). But let's
see what we may do better here...

--
With Best Regards,
Andy Shevchenko