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From:   Rob Herring <robh@kernel.org>
Date:   Tue, 9 Mar 2021 08:48:17 -0700
Message-ID: <CAL_JsqK8FagJyQVyG5DAocUjLGZT91b6NzDm_DNMW1hdCz51Xg@mail.gmail.com>
Subject: Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare
 MMIO as non-posted
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Hector Martin <marcan@marcan.st>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Marc Zyngier <maz@kernel.org>, Olof Johansson <olof@lixom.net>,
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        Mark Kettenis <mark.kettenis@xs4all.nl>,
        Tony Lindgren <tony@atomide.com>,
        Mohamed Mediouni <mohamed.mediouni@caramail.com>,
        Stan Skowronek <stan@corellium.com>,
        Alexander Graf <graf@amazon.com>,
        Will Deacon <will@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
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        Andy Shevchenko <andy.shevchenko@gmail.com>,
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On Mon, Mar 8, 2021 at 2:56 PM Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Mon, Mar 8, 2021 at 10:14 PM Rob Herring <robh@kernel.org> wrote:
> > On Mon, Mar 08, 2021 at 09:29:54PM +0100, Arnd Bergmann wrote:
> > > On Mon, Mar 8, 2021 at 4:56 PM Rob Herring <robh@kernel.org> wrote:
> >
> > Let's just stick with 'nonposted-mmio', but drop 'posted-mmio'. I'd
> > rather know if and when we need 'posted-mmio'. It does need to be added
> > to the DT spec[1] and schema[2] though (GH PRs are fine for both).
>
> I think the reason for having "posted-mmio" is that you cannot properly
> define the PCI host controller nodes on the M1 without that: Since
> nonposted-mmio applies to all child nodes, this would mean the PCI
> memory space gets declared as nonposted by the DT, but the hardware
> requires it to be mapped as posted.

I don't think so. PCI devices wouldn't use any of the code paths in
this patch. They would map their memory space with plain ioremap()
which is posted.

Rob