netdev - Re: [net-next PATCH RFC 07/26] arch/c6x: Add option to skip sync on DMA map and unmap

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Date:   Fri, 28 Oct 2016 10:59:00 -0400
From:   Mark Salter <msalter@...hat.com>
To:     Alexander Duyck <alexander.h.duyck@...el.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     brouer@...hat.com, davem@...emloft.net,
        linux-c6x-dev@...ux-c6x.org, Aurelien Jacquiot <a-jacquiot@...com>
Subject: Re: [net-next PATCH RFC 07/26] arch/c6x: Add option to skip sync on
 DMA map and unmap

On Mon, 2016-10-24 at 08:05 -0400, 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: Mark Salter <msalter@...hat.com>
> Cc: Aurelien Jacquiot <a-jacquiot@...com>
> Cc: linux-c6x-dev@...ux-c6x.org
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
> ---

Acked-by: Mark Salter <msalter@...hat.com>

>  arch/c6x/kernel/dma.c |   16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/c6x/kernel/dma.c b/arch/c6x/kernel/dma.c
> index db4a6a3..d28df74 100644
> --- a/arch/c6x/kernel/dma.c
> +++ b/arch/c6x/kernel/dma.c
> @@ -42,14 +42,17 @@ static dma_addr_t c6x_dma_map_page(struct device *dev, struct page *page,
>  {
>  	dma_addr_t handle = virt_to_phys(page_address(page) + offset);
>  
> -	c6x_dma_sync(handle, size, dir);
> +	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> +		c6x_dma_sync(handle, size, dir);
> +
>  	return handle;
>  }
>  
>  static void c6x_dma_unmap_page(struct device *dev, dma_addr_t handle,
>  		size_t size, enum dma_data_direction dir, unsigned long attrs)
>  {
> -	c6x_dma_sync(handle, size, dir);
> +	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> +		c6x_dma_sync(handle, size, dir);
>  }
>  
>  static int c6x_dma_map_sg(struct device *dev, struct scatterlist *sglist,
> @@ -60,7 +63,8 @@ static int c6x_dma_map_sg(struct device *dev, struct scatterlist *sglist,
>  
>  	for_each_sg(sglist, sg, nents, i) {
>  		sg->dma_address = sg_phys(sg);
> -		c6x_dma_sync(sg->dma_address, sg->length, dir);
> +		if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> +			c6x_dma_sync(sg->dma_address, sg->length, dir);
>  	}
>  
>  	return nents;
> @@ -72,8 +76,10 @@ static void c6x_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
>  	struct scatterlist *sg;
>  	int i;
>  
> -	for_each_sg(sglist, sg, nents, i)
> -		c6x_dma_sync(sg_dma_address(sg), sg->length, dir);
> +	for_each_sg(sglist, sg, nents, i) {
> +		if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> +			c6x_dma_sync(sg_dma_address(sg), sg->length, dir);
> +	}
>  
>  }
>  
>