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In-Reply-To: <ab39d157-a150-3f34-ec3a-047821f7c2a8@samsung.com>
From:   Saravana Kannan <saravanak@google.com>
Date:   Mon, 8 Feb 2021 15:57:42 -0800
Message-ID: <CAGETcx8bK_PXZ_=O+ZG6ef8324qbaqgPNfcuLas6a9KFB_MzHg@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] of: property: Add fw_devlink support for interrupts
To:     Marek Szyprowski <m.szyprowski@samsung.com>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-tegra <linux-tegra@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Jon Hunter <jonathanh@nvidia.com>,
        Marc Zyngier <maz@kernel.org>,
        Kevin Hilman <khilman@baylibre.com>,
        Android Kernel Team <kernel-team@android.com>,
        Rob Herring <robh@kernel.org>,
        Thierry Reding <treding@nvidia.com>
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On Mon, Feb 8, 2021 at 12:14 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
>
> Hi Saravana,
>
> On 06.02.2021 05:32, Saravana Kannan wrote:
> > On Fri, Feb 5, 2021 at 9:55 AM Saravana Kannan <saravanak@google.com> wrote:
> >> On Fri, Feb 5, 2021 at 9:52 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >>> On Fri, Feb 5, 2021 at 6:20 PM Saravana Kannan <saravanak@google.com> wrote:
> >>>> On Fri, Feb 5, 2021 at 2:20 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >>>>> On Fri, Feb 5, 2021 at 11:06 AM Saravana Kannan <saravanak@google.com> wrote:
> >>>>>> On Fri, Feb 5, 2021 at 12:06 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >>>>>>> On Fri, Feb 5, 2021 at 8:38 AM Marek Szyprowski
> >>>>>>> <m.szyprowski@samsung.com> wrote:
> >>>>>>>> On 04.02.2021 22:31, Saravana Kannan wrote:
> >>>>>>>>> On Thu, Feb 4, 2021 at 3:52 AM Marek Szyprowski
> >>>>>>>>> <m.szyprowski@samsung.com> wrote:
> >>>>>>>>>> On 21.01.2021 23:57, Saravana Kannan wrote:
> >>>>>>>>>>> This allows fw_devlink to create device links between consumers of an
> >>>>>>>>>>> interrupt and the supplier of the interrupt.
> >>>>>>>>>>>
> >>>>>>>>>>> Cc: Marc Zyngier <maz@kernel.org>
> >>>>>>>>>>> Cc: Kevin Hilman <khilman@baylibre.com>
> >>>>>>>>>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >>>>>>>>>>> Reviewed-by: Rob Herring <robh@kernel.org>
> >>>>>>>>>>> Reviewed-by: Thierry Reding <treding@nvidia.com>
> >>>>>>>>>>> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> >>>>>>>>>>> Signed-off-by: Saravana Kannan <saravanak@google.com>
> >>>>>>>>>> This patch landed some time ago in linux-next as commit 4104ca776ba3
> >>>>>>>>>> ("of: property: Add fw_devlink support for interrupts"). It breaks MMC
> >>>>>>>>>> host controller operation on ARM Juno R1 board (the mmci@50000 device
> >>>>>>>>>> defined in arch/arm64/boot/dts/arm/juno-motherboard.dtsi). I didn't
> >>>>>>>>> I grepped around and it looks like the final board file is this or
> >>>>>>>>> whatever includes it?
> >>>>>>>>> arch/arm64/boot/dts/arm/juno-base.dtsi
> >>>>>>>> The final board file is arch/arm64/boot/dts/arm/juno-r1.dts
> >>>>>>>>> This patch just finds the interrupt-parent and then tries to use that
> >>>>>>>>> as a supplier if "interrupts" property is listed. But the only
> >>>>>>>>> interrupt parent I can see is:
> >>>>>>>>>           gic: interrupt-controller@2c010000 {
> >>>>>>>>>                   compatible = "arm,gic-400", "arm,cortex-a15-gic";
> >>>>>>>>>
> >>>>>>>>> And the driver uses IRQCHIP_DECLARE() and hence should be pretty much
> >>>>>>>>> a NOP since those suppliers are never devices and are ignored.
> >>>>>>>>> $ git grep "arm,gic-400" -- drivers/
> >>>>>>>>> drivers/irqchip/irq-gic.c:IRQCHIP_DECLARE(gic_400, "arm,gic-400", gic_of_init);
> >>>>>>>>>
> >>>>>>>>> This doesn't make any sense. Am I looking at the right files? Am I
> >>>>>>>>> missing something?
> >>>>>>>> Okay, I've added displaying a list of deferred devices when mounting
> >>>>>>>> rootfs fails and got following items:
> >>>>>>>>
> >>>>>>>> Deferred devices:
> >>>>>>>> 18000000.ethernet        platform: probe deferral - supplier
> >>>>>>>> bus@8000000:motherboard-bus not ready
> >>>>>>>> 1c050000.mmci    amba: probe deferral - supplier
> >>>>>>>> bus@8000000:motherboard-bus not ready
> >>>>>>>> 1c1d0000.gpio    amba: probe deferral - supplier
> >>>>>>>> bus@8000000:motherboard-bus not ready
> >>>>>>>> 2b600000.iommu   platform: probe deferral - wait for supplier
> >>>>>>>> scpi-power-domains
> >>>>>>>> 7ff50000.hdlcd   platform: probe deferral - wait for supplier scpi-clk
> >>>>>>>> 7ff60000.hdlcd   platform: probe deferral - wait for supplier scpi-clk
> >>>>>>>> 1c060000.kmi     amba: probe deferral - supplier
> >>>>>>>> bus@8000000:motherboard-bus not ready
> >>>>>>>> 1c070000.kmi     amba: probe deferral - supplier
> >>>>>>>> bus@8000000:motherboard-bus not ready
> >>>>>>>> 1c170000.rtc     amba: probe deferral - supplier
> >>>>>>>> bus@8000000:motherboard-bus not ready
> >>>>>>>> 1c0f0000.wdt     amba: probe deferral - supplier
> >>>>>>>> bus@8000000:motherboard-bus not ready
> >>>>>>>> gpio-keys
> >>>>>>>> Kernel panic - not syncing: VFS: Unable to mount root fs on
> >>>>>>>> unknown-block(0,0)
> >>>>>>>>
> >>>>>>>> I don't see the 'bus@8000000:motherboard-bus' on the deferred devices
> >>>>>>>> list, so it looks that device core added a link to something that is not
> >>>>>>>> a platform device...
> >>>>>> Probe deferred devices (even platform devices) not showing up in that
> >>>>>> list is not unusual. That's because devices end up on that list only
> >>>>>> after a driver for them is matched and then it fails.
> >>>>>>
> >>>>>>> Lemme guess: bus@8000000 is a simple bus, but it has an
> >>>>>>> interrupt-map, and the devlink code doesn't follow the mapping?
> >>>>>>>
> >>>>>> No, what's happening is that (and this is something I just learned)
> >>>>>> that if a parent has an "#interrupt-cells" property, it becomes your
> >>>>>> interrupt parent. In this case, the motherboard-bus (still a platform
> >>>>>> device) is the parent, but it never probes (because it's simple-bus
> >>>>>> and "arm,vexpress,v2p-p1"). But it becomes the interrupt parent. And
> >>>>>> this mmci device is marked as a consumer of this bus (while still a
> >>>>>> grand-child). Yeah, I'm working on patches (multiple rewrites) to take
> >>>>>> care of cases like this.
> >>>>> One more reason to scrap the different handling of "simple-bus" and
> >>>>> "simple-pm-bus", and use drivers/bus/simple-pm-bus.c, which is a
> >>>>> platform device driver, for both? (like I originally intended ;-)
> >>>> I'm not sure if this will cause more issues since people are used to
> >>>> simple-bus not needing a driver. I'm afraid to open that pandora's
> >>>> box. Maybe last resort if I don't have any other options.
> >>>>
> >>>> But keeping that aside, I'm confused how interrupts are even working
> >>>> if the parent is a DT node with no driver (let alone a device). Any
> >>>> ideas on what's going on or what I'm misunderstanding?
> >>> No driver is needed, as the interrupts are just translated by the map,
> >>> and passed to another interrupt controller, which does have a driver.
> >>>
> >>> Cfr. Section 2.4.3 "Interrupt Nexus Properties" in the DeviceTree
> >>> Specification (https://protect2.fireeye.com/v1/url?k=72fff987-2d64c09f-72fe72c8-0cc47a314e9a-fd7dac11a78508f3&q=1&e=c0dbf5ca-130b-4aac-a011-447e82ca1914&u=https%3A%2F%2Fwww.devicetree.org%2F).
> >>>
> >> Yeah, I need to add interrupt-map support. Sigh. Only so many things I
> >> can fix at a time. Let me know if you want to help.
> >>
> > Marek,
> >
> > After reading the DT spec and poking at the code, I THINK this code is
> > correct. Can you give it a shot? If it works, then I can clean it up,
> > roll in interrupts-extended and send a patch.
>
> Yep, this fixes this issue. Fell free to add:
>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>

Thanks! I'll send out the proper patch.

-Saravana