linux-kernel - Re: [net-next PATCH 04/27] arch/arc: Add option to skip sync on DMA mapping

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Date:   Tue, 25 Oct 2016 15:00:55 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Alexander Duyck <alexander.h.duyck@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
CC:     Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "brouer@...hat.com" <brouer@...hat.com>
Subject: Re: [net-next PATCH 04/27] arch/arc: Add option to skip sync on DMA
 mapping

On 10/25/2016 02:38 PM, Alexander Duyck wrote:
> This change allows us to pass DMA_ATTR_SKIP_CPU_SYNC which allows us to
> avoid invoking cache line invalidation if the driver will just handle it
> later via a sync_for_cpu or sync_for_device call.
>
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: linux-snps-arc@...ts.infradead.org
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
> ---
>  arch/arc/mm/dma.c |    5 ++++-

Acked-by: Vineet Gupta <vgupta@...opsys.com>

>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
> index 20afc65..6303c34 100644
> --- a/arch/arc/mm/dma.c
> +++ b/arch/arc/mm/dma.c
> @@ -133,7 +133,10 @@ static dma_addr_t arc_dma_map_page(struct device *dev, struct page *page,
>  		unsigned long attrs)
>  {
>  	phys_addr_t paddr = page_to_phys(page) + offset;
> -	_dma_cache_sync(paddr, size, dir);
> +
> +	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> +		_dma_cache_sync(paddr, size, dir);
> +
>  	return plat_phys_to_dma(dev, paddr);
>  }
>  
>
>