linux-kernel - Re: [PATCH v2 4/4] clocksource/drivers/timer-mediatek: Make timer-mediatek become loadable module

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Date:   Wed, 15 Feb 2023 17:03:30 -0800
From:   John Stultz <jstultz@...gle.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        walter.chang@...iatek.com,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Maciej W . Rozycki" <macro@...am.me.uk>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        wsd_upstream@...iatek.com, stanley.chu@...iatek.com,
        Chun-hung.Wu@...iatek.com, Freddy.Hsin@...iatek.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v2 4/4] clocksource/drivers/timer-mediatek: Make
 timer-mediatek become loadable module

On Wed, Feb 15, 2023 at 6:46 AM Sudeep Holla <sudeep.holla@....com> wrote:
>
> On Wed, Feb 15, 2023 at 02:30:51PM +0100, AngeloGioacchino Del Regno wrote:
> >
> > Both. I mean that these platforms do have architected timers, but they are stopped
> > before the bootloader jumps to the kernel, or they are never started at all.
> >
> > Please refer to:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/clocksource/timer-mediatek.c?h=next-20230215&id=327e93cf9a59b0d04eb3a31a7fdbf0f11cf13ecb
> >
> > For a nice explanation.
> >
>
> Thanks for that. Well then I see no point in making these modules if you
> can't have generic Image that boots on all the platform. I now tend to think
> that these are made modules just because GKI demands and it *might* work
> on one or 2 platforms. One we move this as modules, how will be know the
> Image without these timers or with them built as modules will boot or not
> on a given mediatek platform. Sorry, I initially saw some point in making
> these timers as modules but if they are required for boot on some systems
> then I see no point. So if that is the case, NACK for these as it just
> creates more confusion after these are merged as why some Images or
> even why defconfig image(if we push the config change as well) is not
> booting on these platforms.

Indeed, if some hardware does have a hard requirement then the
timer-mediatek driver probably isn't a good candidate for being a
module.

Though I wonder if it would make sense to "virtually" split the driver
in two? Have one config for hardware where it is safe to be modular,
and another for the problematic hardware that forces it to be built
in?
That way we can support the safe approach (ends up built in if both
options are selected), but for GKI devices where the hardware isn't
problematic we can still leave it as a module?

thanks
-john