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Subject: Re: [PATCH 13/21] arc: dma-mapping: skip invalidating before
 bidirectional DMA
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To:     Arnd Bergmann <arnd@kernel.org>, linux-kernel@vger.kernel.org
Cc:     Arnd Bergmann <arnd@arndb.de>, Vineet Gupta <vgupta@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
        Brian Cain <bcain@quicinc.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
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        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
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        Stafford Horne <shorne@gmail.com>,
        Helge Deller <deller@gmx.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Rich Felker <dalias@libc.org>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
        "David S. Miller" <davem@davemloft.net>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Christoph Hellwig <hch@lst.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Conor Dooley <conor.dooley@microchip.com>,
        linux-snps-arc@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-oxnas@groups.io,
        linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,
        linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
        linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,
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        linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
        linux-xtensa@linux-xtensa.org,
        Shahab Vahedi <Shahab.Vahedi@synopsys.com>
References: <20230327121317.4081816-1-arnd@kernel.org>
 <20230327121317.4081816-14-arnd@kernel.org>
From:   Vineet Gupta <vgupta@kernel.org>
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CC Shahab

On 3/27/23 17:43, Arnd Bergmann wrote:
> From: Arnd Bergmann<arnd@arndb.de>
>
> Some architectures that need to invalidate buffers after bidirectional
> DMA because of speculative prefetching only do a simpler writeback
> before that DMA, while architectures that don't need to do the second
> invalidate tend to have a combined writeback+invalidate before the
> DMA.
>
> arc is one of the architectures that does both, which seems unnecessary.
>
> Change it to behave like arm/arm64/xtensa instead, and use just a
> writeback before the DMA when we do the invalidate afterwards.
>
> Signed-off-by: Arnd Bergmann<arnd@arndb.de>

Reviewed-by: Vineet Gupta <vgupta@kernel.org>

Shahab can you give this a spin on hsdk - run glibc testsuite over ssh 
and make sure nothing strange happens.

Thx,
-Vineet