linux-kernel - Re: [PATCH 04/12] x86: make dma_cache

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Date:   Thu, 31 Aug 2017 16:06:53 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Christoph Hellwig <hch@....de>
cc:     iommu@...ts.linux-foundation.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Michal Simek <monstr@...str.eu>,
        David Howells <dhowells@...hat.com>,
        Guan Xuetao <gxt@...c.pku.edu.cn>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>, x86@...nel.org,
        linux-mips@...ux-mips.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-xtensa@...ux-xtensa.org,
        linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/12] x86: make dma_cache_sync a no-op

On Sun, 27 Aug 2017, Christoph Hellwig wrote:

> x86 does not implement DMA_ATTR_NON_CONSISTENT allocations, so it doesn't
> make any sense to do any work in dma_cache_sync given that it must be a
> no-op when dma_alloc_attrs returns coherent memory.
> 
> Signed-off-by: Christoph Hellwig <hch@....de

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

> ---
>  arch/x86/include/asm/dma-mapping.h | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
> index 398c79889f5c..04877267ad18 100644
> --- a/arch/x86/include/asm/dma-mapping.h
> +++ b/arch/x86/include/asm/dma-mapping.h
> @@ -70,7 +70,6 @@ static inline void
>  dma_cache_sync(struct device *dev, void *vaddr, size_t size,
>  	enum dma_data_direction dir)
>  {
> -	flush_write_buffers();
>  }
>  
>  static inline unsigned long dma_alloc_coherent_mask(struct device *dev,
> -- 
> 2.11.0
> 
>