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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 12 Feb 2019 12:55:17 +0100
Message-ID: <CAK8P3a1gmJTt+jdTbdSYZ0z43qodxf+co757K1-Hq1mj4fCqQA@mail.gmail.com>
Subject: Re: [PATCH 1/2] asm-generic/io: Pass result on inX() accessor to __io_par()
To:     Will Deacon <will.deacon@arm.com>
Cc:     linux-arch <linux-arch@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        andrew.murray@arm.com, Catalin Marinas <catalin.marinas@arm.com>,
        linux-riscv@lists.infradead.org,
        Palmer Dabbelt <palmer@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>
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On Mon, Feb 11, 2019 at 6:45 PM Will Deacon <will.deacon@arm.com> wrote:
>
> The inX() I/O accessors must enforce ordering against subsequent calls
> to the delay() routines, so that a read-back from a device can be used
> to postpone a subsequent write to the same device.
>
> On some architectures, including arm64, this ordering can only be
> achieved by creating a dependency on the value returned by the inX()
> operation, so we need to pass the value we read to the __io_par()
> macro in this case.
>
> Reported-by: Andrew Murray <andrew.murray@arm.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>  include/asm-generic/io.h | 8 ++++----

For changing the asm-generic file in the arm64 tree,

Acked-by: Arnd Bergmann <arnd@arndb.de>

For all I can see, this should not conflict with the usage of the
same macros on RISC-V, though it does make add a significant
difference, so I'd like to see an Ack from the RISC-V folks as
well (added to Cc), or possibly a change to arch/riscv/include/asm/io.h
to do a corresponding change.

       Arnd