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

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Message-ID: <CAHp75Ven4piceFaBhn1kc=vtwM4o-GXmz3eAZoNhU8w+iP5qxQ@mail.gmail.com>
Date:   Fri, 5 Mar 2021 16:45:53 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Hector Martin <marcan@...can.st>
Cc:     linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Marc Zyngier <maz@...nel.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>,
        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 <devicetree@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Documentation List <linux-doc@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <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, Mar 4, 2021 at 11:40 PM 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.

Hmm... But isn't it basically a requirement to those device drivers to
use readX()/writeX() instead of readX_relaxed() / writeX_relaxed()?

...

>  #define IORESOURCE_MEM_32BIT           (3<<3)
>  #define IORESOURCE_MEM_SHADOWABLE      (1<<5)  /* dup: IORESOURCE_SHADOWABLE */
>  #define IORESOURCE_MEM_EXPANSIONROM    (1<<6)
> +#define IORESOURCE_MEM_NONPOSTED       (1<<7)

Not sure it's the right location (in a bit field) for this flag.

-- 
With Best Regards,
Andy Shevchenko