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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Mon, 23 May 2022 11:36:29 +0200
Message-ID: <CAK8P3a2cP8Y42C4kCbFSpkcj8cLexinLj=x9m6vvwKJxLvX7yw@mail.gmail.com>
Subject: Re: [PATCH v3 1/2] asm-generic: Add memory barrier dma_mb()
To:     Kefeng Wang <wangkefeng.wang@huawei.com>
Cc:     Marco Elver <elver@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
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On Mon, May 23, 2022 at 4:00 AM Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>
> The memory barrier dma_mb() is introduced by commit a76a37777f2c
> ("iommu/arm-smmu-v3: Ensure queue is read after updating prod pointer"),
> which is used to ensure that prior (both reads and writes) accesses
> to memory by a CPU are ordered w.r.t. a subsequent MMIO write, this
> is only defined on arm64, but it is a generic memory barrier, let's
> add dma_mb() into documentation and include/asm-generic/barrier.h.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---

I assume you plan this to get merged through the arm64 tree.

Reviewed-by: Arnd Bergmann <arnd@arndb.de> # for asm-generic