linux-kernel - Re: [PATCH 1/2] irqchip: irq-meson-gpio: make it possible to build as a module

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Message-ID: <CAGETcx-XEJ25SvUO92wVyqjna+=CU6UTSQKqDimy008z0afA1g@mail.gmail.com>
Date:   Tue, 3 Aug 2021 19:11:58 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Kevin Hilman <khilman@...libre.com>,
        Lee Jones <lee.jones@...aro.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] irqchip: irq-meson-gpio: make it possible to build as
 a module

On Tue, Aug 3, 2021 at 2:51 AM Marc Zyngier <maz@...nel.org> wrote:
>
> On Tue, 03 Aug 2021 10:44:34 +0100,
> Marc Zyngier <maz@...nel.org> wrote:
>
> [...]
>
> > This thing keeps failing on my end. It only works if I force the
> > irqchip module to be present before the MDIO module is loaded. Here's
> > an example:
> >
> > root@...er-roach:~# modprobe mdio_mux_meson_g12a
> > [  125.871544] libphy: mdio_mux: probed
> > [  125.882575] g12a-mdio_mux ff64c000.mdio-multiplexer: Error: Failed to register MDIO bus for child /soc/bus@...00000/mdio-multiplexer@...00/mdio@0
> > [  125.892630] libphy: mdio_mux: probed
> >
> > Trying to bring up the Ethernet interface will fail. Note that there
> > was no attempt to load the irqchip driver.
> >
> > root@...er-roach:~# modprobe -r mdio_mux_meson_g12a
> > root@...er-roach:~# modprobe irq-meson-gpio
> > [  144.983344] meson-gpio-intc ffd0f080.interrupt-controller: 100 to 8 gpio interrupt mux initialized
> > root@...er-roach:~# modprobe mdio_mux_meson_g12a
> > [  150.376464] libphy: mdio_mux: probed
> > [  150.391039] libphy: mdio_mux: probed
> >
> > And it now works.
>
> An additional source of amusement is that this patch allows the
> irqchip to be removed from the kernel. It becomes really fun when you
> have live interrupts...

Which is why I wrote IRQCHIP_PLATFORM_DRIVER_BEGIN/END macros. Maybe
those should be used instead?

-Saravana

[1] - https://lore.kernel.org/lkml/20200718000637.3632841-2-saravanak@google.com/