linux-kernel - Re: [PATCH] bus: simple-pm-bus: fix forced runtime PM use

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Message-ID: <CAMuHMdXD1yF65ezOmLz2ShP=gnYNNkUfTLfY8RA0m=C+WwtaVw@mail.gmail.com>
Date: Fri, 14 Feb 2025 14:16:14 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Johan Hovold <johan@...nel.org>
Cc: Ulf Hansson <ulf.hansson@...aro.org>, Johan Hovold <johan+linaro@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Liu Ying <victor.liu@....com>
Subject: Re: [PATCH] bus: simple-pm-bus: fix forced runtime PM use

Hi Johan,

On Fri, 14 Feb 2025 at 13:53, Johan Hovold <johan@...nel.org> wrote:
> On Fri, Feb 14, 2025 at 01:36:48PM +0100, Ulf Hansson wrote:
> > On Fri, 14 Feb 2025 at 11:21, Johan Hovold <johan+linaro@...nel.org> wrote:
> > >
> > > The simple-pm-bus driver only enables runtime PM for some buses
> > > ('simple-pm-bus') yet has started calling pm_runtime_force_suspend() and
> > > pm_runtime_force_resume() during system suspend unconditionally.
> > >
> > > This currently works, but that is not obvious and depends on
> > > implementation details which may change at some point.
> > >
> > > Add dedicated system sleep ops and only call pm_runtime_force_suspend()
> > > and pm_runtime_force_resume() for buses that use runtime PM to avoid any
> > > future surprises.

Thanks for your patch!

> > > Fixes: c45839309c3d ("drivers: bus: simple-pm-bus: Use clocks")
> >
> > This doesn't look like it is needed to me. It isn't broken, right?
>
> I didn't add a CC stable tag since this currently works, but I still
> consider it a bug to call these helpers unconditionally when not using
> runtime PM.

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

> [ And during rc1 these callbacks were suddenly called and triggered a
> NULL-pointer dereference as you know. [1] ]
>
> Johan
>
> [1] https://lore.kernel.org/lkml/Z6YcjFBWAVVVANf2@hovoldconsulting.com/

Thanks, that was the context I needed to raise review priority ;)

Perhaps Reported-by: and Closes:?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds