linux-kernel - Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

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Date:   Wed, 20 Apr 2022 11:53:24 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     "hch@....de" <hch@....de>
Cc:     Arnd Bergmann <arnd@...db.de>, Sven Peter <sven@...npeter.dev>,
        Keith Busch <kbusch@...nel.org>, "axboe@...com" <axboe@...com>,
        "sagi@...mberg.me" <sagi@...mberg.me>,
        Hector Martin <marcan@...can.st>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvme@...ts.infradead.org, linux-spdx@...r.kernel.org
Subject: Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

On Wed, Apr 20, 2022 at 6:34 AM hch@....de <hch@....de> wrote:
> On Tue, Apr 19, 2022 at 11:52:15AM +0200, Arnd Bergmann wrote:
> > > I just checked again and 64-bit accesses seem to work fine.
> > > I'll remove the lo_hi_* calls and this include.
> >
> > If you remove the #include, it is no longer possible to compile-test
> > this on all 32-bit architectures, though that is probably fine as long
> > as the Kconfig file has the right dependencies, like
> >
> >       depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
> >
> > I'd prefer to keep the #include here, but I don't mind the dependency
> > if Christoph prefers it that way.
>
> So thre's really two steps here:
>
>  1) stop uing lo_hi_readq diretly which forces 32-bit access even on
>     64-bit platforms
>  2) stop using the io-64-nonatomic headers entirely
>
> I definitively want 1) done if the hardware does not require it.

Yes, of cours.e

> Trying to cater to 32-bit build tests on hardware that has no chance of
> ever being used there by including the header seems a bit silly, but if
> it makes folks happy I can live with it.

As I said, I don't have a strong opinion either, it's either a trivial change
in Kconfig or a trivial header inclusion and I'd pick the header one because
it's more obvious what this is for without adding a comment.

      Arnd