linux-kernel - Re: [PATCH 0/2] irq-meson-gpio: make it possible to build as a module

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Date:   Mon, 26 Oct 2020 09:18:21 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Marc Zyngier <maz@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>
Cc:     jbrunet@...libre.com, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] irq-meson-gpio: make it possible to build as a module

Marc Zyngier <maz@...nel.org> writes:

> On Tue, 20 Oct 2020 08:25:30 +0100,
> Neil Armstrong <narmstrong@...libre.com> wrote:
>> 
>> In order to reduce the kernel Image size on multi-platform distributions,
>> make it possible to build the Amlogic GPIO IRQ controller as a module
>> by switching it to a platform driver.
>> 
>> The second patch removes MESON_IRQ_GPIO selection from ARCH_MESON to allow
>> building the driver as module.
>> 
>> Neil Armstrong (2):
>>   irqchip: irq-meson-gpio: make it possible to build as a module
>>   arm64: meson: remove MESON_IRQ_GPIO selection
>> 
>>  arch/arm64/Kconfig.platforms     |  1 -
>>  drivers/irqchip/Kconfig          |  5 +-
>>  drivers/irqchip/irq-meson-gpio.c | 89 ++++++++++++++++++++------------
>>  3 files changed, 59 insertions(+), 36 deletions(-)
>
> I've tried this series on my vim3l with the this driver compiled as a
> module, and lost the Ethernet interface in the process, as the phy
> wasn't able to resolve its interrupt and things fail later on:
>
> [   72.238291] meson8b-dwmac ff3f0000.ethernet eth1: no phy at addr -1
> [   72.238917] meson8b-dwmac ff3f0000.ethernet eth1: stmmac_open: Cannot attach to PHY (error: -19)
>
> This is a generic problem with making DT-based interrupt controllers
> modular when not *all* the drivers can deal with probing deferral.

Yes, but this series still keeps the default as built-in.

If you build as a module, and you add `fw_devlink=on` to the kernel
command-line, device-links will be created based on DT dependencies 
which will ensure the right module load order.

I've tested this series with `fw_devlink=on` on several Amlogic
platforms and it works just fine, but since it requires the extra
cmdline option, I think the default should remain built-in.

So, I'd still like to see this series merged so that at least it's an
option to enable this as a module.

Also, another reason to make it optional is that not all platforms need
this feature at all, but right now we select it for all Amlogic SoCs.

Kevin