linux-kernel - Re: [PATCH 07/11] powerpc: make dma_cache

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Date:   Tue, 3 Oct 2017 13:24:57 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Christoph Hellwig <hch@....de>, iommu@...ts.linux-foundation.org
Cc:     Chris Zankel <chris@...kel.net>, Michal Simek <monstr@...str.eu>,
        linux-ia64@...r.kernel.org, linux-mips@...ux-mips.org,
        linux-sh@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-xtensa@...ux-xtensa.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Guan Xuetao <gxt@...c.pku.edu.cn>,
        Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 07/11] powerpc: make dma_cache_sync a no-op



Le 03/10/2017 à 12:43, Christoph Hellwig a écrit :
> powerpc 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.
What about arch/powerpc/mm/dma-noncoherent.c ?

Powerpc 8xx doesn't have coherent memory.

Christophe

> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   arch/powerpc/include/asm/dma-mapping.h | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/include/asm/dma-mapping.h
> index eaece3d3e225..320846442bfb 100644
> --- a/arch/powerpc/include/asm/dma-mapping.h
> +++ b/arch/powerpc/include/asm/dma-mapping.h
> @@ -144,8 +144,6 @@ static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
>   static inline void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
>   		enum dma_data_direction direction)
>   {
> -	BUG_ON(direction == DMA_NONE);
> -	__dma_sync(vaddr, size, (int)direction);
>   }
>   
>   #endif /* __KERNEL__ */
>