From: Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH RFC 0/3] API for 128-bit IO access
Date: Wed, 24 Jan 2018 10:22:13 +0000
Message-ID: <20180124102212.GC20586@arm.com>
References: <20180124090519.6680-1-ynorov@caviumnetworks.com>
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Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrew Pinski <Andrew.Pinski@cavium.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        "David S . Miller" <davem@davemloft.net>,
        Geethasowjanya Akula <Geethasowjanya.Akula@cavium.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Sunil Goutham <Sunil.Goutham@cavium.com>
To: Yury Norov <ynorov@caviumnetworks.com>
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On Wed, Jan 24, 2018 at 12:05:16PM +0300, Yury Norov wrote:
> This series adds API for 128-bit memory IO access and enables it for ARM64.
> The original motivation for 128-bit API came from new Cavium network device
> driver. The hardware requires 128-bit access to make things work. See
> description in patch 3 for details.
> 
> Also, starting from ARMv8.4, stp and ldp instructions become atomic, and
> API for 128-bit access would be helpful in core arm64 code.

Only for normal, cacheable memory, so they're not suitable for IO accesses
as you're proposing here.

Will