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_VtJXCqih4ZadZ0dFVJwKOBEQnnrr9JxxmGNh7HX_vNQ@mail.gmail.com>
Date:   Tue, 19 May 2020 11:02:49 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Marek Szyprowski <m.szyprowski@...sung.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>,
        LKML <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 Samsung SOC <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH v1 4/4] of: platform: Batch fwnode parsing when adding all
 top level devices

On Tue, May 19, 2020 at 3:32 AM Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
>
> Hi
>
> On 19.05.2020 09:11, Marek Szyprowski wrote:
> > On 19.05.2020 08:48, Saravana Kannan wrote:
> >> On Mon, May 18, 2020 at 11:25 PM Marek Szyprowski
> >> <m.szyprowski@...sung.com> wrote:
> >>> On 15.05.2020 07:35, Saravana Kannan wrote:
> >>>> The fw_devlink_pause() and fw_devlink_resume() APIs allow batching the
> >>>> parsing of the device tree nodes when a lot of devices are added. This
> >>>> will significantly cut down parsing time (as much a 1 second on some
> >>>> systems). So, use them when adding devices for all the top level
> >>>> device
> >>>> tree nodes in a system.
> >>>>
> >>>> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> >>> This patch recently landed in linux-next 20200518. Sadly, it causes
> >>> regression on Samsung Exynos5433-based TM2e board:
> >>>
> >>> ...
> >>>
> >>> Both issues, the lack of DMA for SPI device and Synchronous abort in
> >>> I2S
> >>> probe are new after applying this patch. I'm trying to investigate
> >>> which
> >>> resources are missing and why. The latter issue means typically that
> >>> the
> >>> registers for the given device has been accessed without enabling the
> >>> needed clocks or power domains.
> >> Did you try this copy-pasta fix that I sent later?
> >> https://lore.kernel.org/lkml/20200517173453.157703-1-saravanak@google.com/
> >>
> >>
> >> Not every system would need it (my test setup didn't), but it helps
> >> some cases.
> >>
> >> If that fix doesn't help, then some tips for debugging the failing
> >> drivers.
> >> What this pause/resume patch effectively (not explicitly) does is:
> >> 1. Doesn't immediately probe the devices as they are added in
> >> of_platform_default_populate_init()
> >> 2. Adds them in order to the deferred probe list.
> >> 3. Then kicks off deferred probe on them in the order they were added.
> >>
> >> These drivers are just not handling -EPROBE_DEFER correctly or
> >> assuming probe order and that's causing these issues.
> >>
> >> So, we can either fix that or you can try adding some code to flush
> >> the deferred probe workqueue at the end of fw_devlink_resume().
> >>
> >> Let me know how it goes.
> >
> > So far it looks that your patch revealed a hidden issue in exynos5433
> > clocks configuration, because adding clk_ignore_unused parameter to
> > kernel command line fixes the boot. I'm still investigating it, so
> > probable you can ignore my regression report. I will let you know asap
> > I finish checking it.
> >
> Okay, I confirm that the issue is in the Exynos I2S driver and
> Exynos5433 clock provider. I've posted a quick workaround. I'm sorry for
> the noise, your patch is fine.

Thanks for debugging and finding the real issue. I tried finding your
patches, but couldn't. Can you point me to a lore.kernel.org link? I'm
just curious to see what the issue was.

I'm guessing you didn't need to pick up this one?
https://lore.kernel.org/lkml/20200517173453.157703-1-saravanak@google.com/

-Saravana