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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 18 Jan 2021 20:16:33 +0100
Message-ID: <CAMuHMdUUX22D7gV-LtDJ4jcxD=TD6soWzP=gUy4EqdFFAntoGA@mail.gmail.com>
Subject: Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default
To:     Marc Zyngier <maz@kernel.org>
Cc:     Saravana Kannan <saravanak@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Android Kernel Team <kernel-team@android.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Jisheng Zhang <Jisheng.Zhang@synaptics.com>,
        Kevin Hilman <khilman@baylibre.com>,
        John Stultz <john.stultz@linaro.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>
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Hi Marc,

On Mon, Jan 18, 2021 at 6:59 PM Marc Zyngier <maz@kernel.org> wrote:
> On 2021-01-18 17:39, Geert Uytterhoeven wrote:
> > On Fri, Dec 18, 2020 at 4:34 AM Saravana Kannan <saravanak@google.com>
> > wrote:
> >> Cyclic dependencies in some firmware was one of the last remaining
> >> reasons fw_devlink=on couldn't be set by default. Now that cyclic
> >> dependencies don't block probing, set fw_devlink=on by default.
> >>
> >> Setting fw_devlink=on by default brings a bunch of benefits
> >> (currently,
> >> only for systems with device tree firmware):
> >> * Significantly cuts down deferred probes.
> >> * Device probe is effectively attempted in graph order.
> >> * Makes it much easier to load drivers as modules without having to
> >>   worry about functional dependencies between modules (depmod is still
> >>   needed for symbol dependencies).
> >>
> >> If this patch prevents some devices from probing, it's very likely due
> >> to the system having one or more device drivers that "probe"/set up a
> >> device (DT node with compatible property) without creating a struct
> >> device for it.  If we hit such cases, the device drivers need to be
> >> fixed so that they populate struct devices and probe them like normal
> >> device drivers so that the driver core is aware of the devices and
> >> their
> >> status. See [1] for an example of such a case.
> >>
> >> [1] -
> >> https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@mail.gmail.com/
> >> Signed-off-by: Saravana Kannan <saravanak@google.com>
> >
> > Shimoda-san reported that next-20210111 and later fail to boot
> > on Renesas R-Car Gen3 platforms. No output is seen, unless earlycon
> > is enabled.
> >
> > I have bisected this to commit e590474768f1cc04 ("driver core: Set
> > fw_devlink=on by default").
>
> There is a tentative patch from Saravana here[1], which works around
> some issues on my RK3399 platform, and it'd be interesting to find
> out whether that helps on your system.
>
> Thanks,
>
>          M.
>
> [1]
> https://lore.kernel.org/r/20210116011412.3211292-1-saravanak@google.com

Thanks for the suggestion, but given no devices probe (incl. GPIO
providers), I'm afraid it won't help. [testing] Indeed.

With the debug prints in device_links_check_suppliers enabled, and
some postprocessing, I get:

    255 supplier e6180000.system-controller not ready
      9 supplier fe990000.iommu not ready
      9 supplier fe980000.iommu not ready
      6 supplier febd0000.iommu not ready
      6 supplier ec670000.iommu not ready
      3 supplier febe0000.iommu not ready
      3 supplier e7740000.iommu not ready
      3 supplier e6740000.iommu not ready
      3 supplier e65ee000.usb-phy not ready
      3 supplier e6570000.iommu not ready
      3 supplier e6054000.gpio not ready
      3 supplier e6053000.gpio not ready

As everything is part of a PM Domain, the (lack of the) system controller
must be the culprit. What's wrong with it? It is registered very early in
the boot:

[    0.142096] rcar_sysc_pd_init:442: of_genpd_add_provider_onecell() returned 0

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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