From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vineet Gupta <vgupta@kernel.org>
Subject: Re: [PATCH 13/21] arc: dma-mapping: skip invalidating before
 bidirectional DMA
Date: Sun, 2 Apr 2023 12:22:20 +0530
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References: <20230327121317.4081816-1-arnd@kernel.org>
 <20230327121317.4081816-14-arnd@kernel.org>
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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>, Michal Simek <monstr@monstr.eu>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, Dinh Nguyen <dinguyen@kernel.org>, 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

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