linux-kernel - Re: [PATCH v1 4/4] of: platform: Batch fwnode parsing when adding all top level devices

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Message-ID: <CAGETcx_gOQWbxUAS6joxEgLDx_wuXwn3AFqDuio_42XeeG++PQ@mail.gmail.com>
Date:   Wed, 24 Jun 2020 16:22:40 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Len Brown <lenb@...nel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Ji Luo <ji.luo@....com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v1 4/4] of: platform: Batch fwnode parsing when adding all
 top level devices

On Mon, Jun 22, 2020 at 8:49 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Saravana,
>
> On Sat, Jun 20, 2020 at 4:33 AM Saravana Kannan <saravanak@...gle.com> wrote:
> > On Fri, Jun 19, 2020 at 1:07 PM Saravana Kannan <saravanak@...gle.com> wrote:
> > > I think instead of deferred_probe_work_func() moving the device to the
> > > end of the dpm_list, I think the device probing successfully is what
> > > should move it to the end of the dpm_list. That way, the dpm_list is
> > > actually ordered by when the devices become functional and not the
> > > random order in DT or random probe order which can get pretty
> > > convoluted with multiple deferred probes. This feels right and will
> > > make suspend/resume more robust against DT ordering -- but I'm not
> > > sure what other wide ranging impact this has for other platforms.
> >
> > If you want to play around with a potential fix to test my hypothesis,
> > I think it's just adding this one line to driver_bound():
> > ============
> > klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
> > device_links_driver_bound(dev);
> > +device_pm_move_to_tail(dev);
> >
> > device_pm_check_callbacks(dev);
> > ============
>
> Thanks, that seems to fix the issue for me, on both affected systems!
> Note that this has quite some impact on the order devices are suspended,
> but this seems harmless.
>
> Will try on more systems later...

Thanks for testing. Maybe I should just send that change as a patch
and see what Greg/Rafael have to say to that.

It's a general fix anyway. So, might as well send it out.

-Saravana