linux-kernel - Re: [PATCH] arch64: export __flush_dcache

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Message-ID: <20190517215303.3daebi7o66we2cjh@mbp>
Date:   Fri, 17 May 2019 22:53:04 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Mark Salyzyn <salyzyn@...roid.com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arch64: export __flush_dcache_area

On Fri, May 17, 2019 at 12:59:56PM -0700, Mark Salyzyn wrote:
> Some (out of tree modular) drivers feel a need to ensure
> data is flushed to the DDR before continuing flow.
> 
> Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
> Cc: linux-kernel@...r.kernel.org
> Cc: kernel-team@...roid.com
> ---
>  arch/arm64/mm/cache.S | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
> index a194fd0e837f..70d7cb5c0bd2 100644
> --- a/arch/arm64/mm/cache.S
> +++ b/arch/arm64/mm/cache.S
> @@ -120,6 +120,7 @@ ENTRY(__flush_dcache_area)
>  	dcache_by_line_op civac, sy, x0, x1, x2, x3
>  	ret
>  ENDPIPROC(__flush_dcache_area)
> +EXPORT_SYMBOL_GPL(__flush_dcache_area)
>  
>  /*
>   *	__clean_dcache_area_pou(kaddr, size)

NAK. Such drivers are doing something wrong, there is a dedicated
in-kernel API for that handles kernel maintenance (hint: DMA).

-- 
Catalin