linux-kernel - Re: [PATCH 05/10] swiotlb: merge swiotlb_unmap_page and unmap

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Date:   Thu, 18 Oct 2018 18:44:32 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Christoph Hellwig <hch@....de>, Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/10] swiotlb: merge swiotlb_unmap_page and unmap_single

On 08/10/18 09:02, Christoph Hellwig wrote:
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   kernel/dma/swiotlb.c | 15 ++++-----------
>   1 file changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 11dbcd80b4a6..15335f3a1bf3 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -765,9 +765,9 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
>    * After this call, reads by the cpu to the buffer are guaranteed to see
>    * whatever the device wrote there.
>    */
> -static void unmap_single(struct device *hwdev, dma_addr_t dev_addr,
> -			 size_t size, enum dma_data_direction dir,
> -			 unsigned long attrs)
> +void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
> +			size_t size, enum dma_data_direction dir,
> +			unsigned long attrs)
>   {
>   	phys_addr_t paddr = dma_to_phys(hwdev, dev_addr);
>   
> @@ -790,13 +790,6 @@ static void unmap_single(struct device *hwdev, dma_addr_t dev_addr,
>   	dma_mark_clean(phys_to_virt(paddr), size);
>   }
>   
> -void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
> -			size_t size, enum dma_data_direction dir,
> -			unsigned long attrs)
> -{
> -	unmap_single(hwdev, dev_addr, size, dir, attrs);
> -}
> -
>   /*
>    * Make physical memory consistent for a single streaming mode DMA translation
>    * after a transfer.
> @@ -900,7 +893,7 @@ swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
>   	BUG_ON(dir == DMA_NONE);

In passing, I notice that this BUG_ON(), and its friends elsewhere in 
the file, appear entirely pointless, since the wrappers in dma-mapping.h 
have already made the equivalent check.

For this patch, though,

Reviewed-by: Robin Murphy <robin.murphy@....com>

>   
>   	for_each_sg(sgl, sg, nelems, i)
> -		unmap_single(hwdev, sg->dma_address, sg_dma_len(sg), dir,
> +		swiotlb_unmap_page(hwdev, sg->dma_address, sg_dma_len(sg), dir,
>   			     attrs);
>   }
>   
>