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

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Message-ID: <CAMuHMdUsWAQ3XUGh1Jg_Y3LWz4G5aaZfHqL8JjNZv3DrW3TjvQ@mail.gmail.com>
Date:   Mon, 22 Jun 2020 17:49:13 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Saravana Kannan <saravanak@...gle.com>
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

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...

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