linux-kernel - Re: [RFT PATCH v3 08/27] asm-generic/io.h: Add a non-posted variant of ioremap()

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Date:   Mon, 08 Mar 2021 11:20:57 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Hector Martin <marcan@...can.st>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh@...nel.org>, Arnd Bergmann <arnd@...nel.org>,
        Olof Johansson <olof@...om.net>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        Tony Lindgren <tony@...mide.com>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Stan Skowronek <stan@...ellium.com>,
        Alexander Graf <graf@...zon.com>,
        Will Deacon <will@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Hellwig <hch@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        devicetree@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFT PATCH v3 08/27] asm-generic/io.h:  Add a non-posted variant of ioremap()

On Thu, 04 Mar 2021 21:38:43 +0000,
Hector Martin <marcan@...can.st> wrote:
> 
> ARM64 currently defaults to posted MMIO (nGnRnE), but some devices
> require the use of non-posted MMIO (nGnRE). Introduce a new ioremap()
> variant to handle this case. ioremap_np() is aliased to ioremap() by
> default on arches that do not implement this variant.
> 
> sparc64 is the only architecture that needs to be touched directly,
> because it includes neither of the generic io.h or iomap.h headers.
> 
> This adds the IORESOURCE_MEM_NONPOSTED flag, which maps to this
> variant and marks a given resource as requiring non-posted mappings.
> This is implemented in the resource system because it is a SoC-level
> requirement, so existing drivers do not need special-case code to pick
> this ioremap variant.
> 
> Then this is implemented in devres by introducing devm_ioremap_np(),
> and making devm_ioremap_resource() automatically select this variant
> when the resource has the IORESOURCE_MEM_NONPOSTED flag set.
> 
> Signed-off-by: Hector Martin <marcan@...can.st>

Acked-by: Marc Zyngier <maz@...nel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.