linux-kernel - Re: [PATCH v2 1/2] of: platform: Make sure bus only devices get probed

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Message-ID: <CAMuHMdWNP1yn0ouJzgYpvQkdAHAA4_gf8z+iZWpbftvGN5a+qQ@mail.gmail.com>
Date:   Fri, 3 Sep 2021 21:06:00 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] of: platform: Make sure bus only devices get probed

Hi Saravana,

On Fri, Sep 3, 2021 at 7:09 PM Saravana Kannan <saravanak@...gle.com> wrote:
> On Fri, Sep 3, 2021 at 7:29 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Fri, Sep 3, 2021 at 11:19 AM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> > > On Fri, 3 Sept 2021 at 01:04, Saravana Kannan <saravanak@...gle.com> wrote:
> > > > fw_devlink could end up creating device links for bus only devices.
> > > > However, bus only devices don't get probed and can block probe() or
> > > > sync_state() [1] call backs of other devices. To avoid this, set up
> > > > these devices to get probed by the simple-pm-bus.
> > > >
> > > > [1] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@mail.gmail.com/
> > > > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > > > Tested-by: Saravana Kannan <saravanak@...gle.com>
> > >
> > > Again, this looks like a nice solution to the problem.
> > >
> > > One question though. The Kconfig SIMPLE_PM_BUS, should probably be
> > > "default y" - or something along those lines to make sure fw_devlink
> > > works as expected.
> >
> > I would love for SIMPLE_PM_BUS to go away, and all of its functionality
> > to be usurped by the standard simple-bus handling.
>
> What if SIMPLE_PM_BUS *is* the standard simple-bus handling?
> Insert "I'm the captain now" meme.

No objections from my side.  In fact that's how I wanted it to be
from the beginning, but the DT people wanted a separate compatible
value (and a separate driver).  The only difference is the presence
of pm_runtime_*() calls.

> I think SIMPLE_PM_BUS config should just go away and we should compile
> the driver in if CONFIG_OF is selected.

I think there would be no need for a separate driver, if the standard
simple-bus handling would take care of it.

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