linux-kernel - Re: [PATCH] Revert "irqchip/mtk-sysirq: Convert to a platform driver"

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Date:   Fri, 21 Aug 2020 11:17:36 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Frank Wunderlich <wichtig@...web.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Collabora Kernel ML <kernel@...labora.com>,
        Frank Wunderlich <linux@...web.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Hanks Chen <hanks.chen@...iatek.com>,
        Jason Cooper <jason@...edaemon.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH] Revert "irqchip/mtk-sysirq: Convert to a platform driver"

Hi Enric,

On 2020-08-21 10:20, Enric Balletbo i Serra wrote:
> Hi Marc,
> 
> On 20/8/20 16:53, Marc Zyngier wrote:
>> On 2020-08-20 09:07, Saravana Kannan wrote:
>>> On Thu, Aug 20, 2020 at 12:56 AM Marc Zyngier <maz@...nel.org> wrote:
>>>> 
>>>> On 2020-08-19 19:51, Saravana Kannan wrote:
>>>> > On Wed, Aug 19, 2020 at 9:52 AM Frank Wunderlich <wichtig@...web.de>
>>>> > wrote:
>>>> >>
>>>> >> hi,
>>>> >>
>>>> >> does the fix you've linked to my revert [1] not work in your case?
>>>> >>
>>>> >> [1] https://patchwork.kernel.org/patch/11718481/
>>>> >
>>>> > Thanks for pointing it out Frank. Also, might want to avoid top
>>>> > posting in the future.
>>>> >
>>>> > Enric, Can you please try that other fix and see if that solves your
>>>> > issue?
>>>> 
>>>> I think Enric was clear that the driver does probe correctly
>>>> (meaning that he has the fix in his tree). It is everything else
>>>> that breaks, because none of the drivers on the platform are
>>>> equipped to defer their own probing.
>>>> 
>>>> I think we need to change this works right now, meaning that we 
>>>> can't
>>>> blindly change the behaviour of *built-in* drivers. I'll see if I 
>>>> can
>>>> come up with something quickly, but I'll otherwise take Enric patch.
>>> 
>>> Sounds fair Marc.
>>> 
>>> Btw, Enric, out of curiosity, can you try adding "fw_devlink=on" to
>>> your kernel command line to see if it helps? It basically ensures
>>> proper probe ordering without depending on the drivers. There are 
>>> some
>>> corner cases where it still can't work properly (too much to explain
>>> for a late night email), but if the platforms don't have those corner
>>> cases it'll work perfectly.
>>> 
>>> I'm fine with the revert if Marc isn't able to find a quick fix to 
>>> the
>>> drivers, but this might also fix your problem right away.
>> 
>> I'm afraid there is no quick fix if we want to preserve the current
>> behavior with built-in drivers, and not having "fw_devlink=on" by
>> default makes it irrelevant for most people.
>> 
>> fw_devlink also prevents my test platforms from booting (my rk3399
>> doesn't find its PCI devices with it), while the same kernel boots
>> just fine without it. It could well be that the corner case is
>> likely to be more prevalent than you seem to expect.
>> 
>> I will probably end-up end-up queuing reverts for both mtk-sysirq,
>> mtk-cirq, and qcom-pdc (the first two can't be built as module with
>> mainline anyway, and I seem to remember that the latter caused some
>> controversy as well).
>> 
>> As an experiment, I have pushed out a branch[1] that implements
>> a "hybrid" probe, retaining the previous early probe mechanism when
>> the driver is built-in, and letting things rip when built as a
>> module (if you do that, you hopefully know what you are doing).
>> I'd welcome some testing on affected platforms (I don't have
>> anything I can run mainline on that'd be affected).
>> 
> 
> Unfortunately, my Kukui (MT8183) board doesn't boot at all with those 
> patches. I
> only did a quick test and I didn't dig further, please let me know if 
> you want I
> debug more the issue. IMHO, right now, the revert seems to be the 
> better
> solution for this cycle.

It'd be good if you could help with that, but I will definitely apply
the revert (below for the revert list). Any change is too invasive to
be added to this cycle.

920ecb8c35cb irqchip/mtk-cirq: Convert to a platform driver
f97dbf48ca43 irqchip/mtk-sysirq: Convert to a platform driver
5be57099d445 irqchip/qcom-pdc: Switch to using IRQCHIP_PLATFORM_DRIVER 
helper macros
95bf9305d2e3 irqchip/qcom-pdc: Allow QCOM_PDC to be loadable as a 
permanent module

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...