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From: Will Deacon <will@kernel.org>
To: David Stevens <stevensd@chromium.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
	Joerg Roedel <joro@8bytes.org>,
	Lu Baolu <baolu.lu@linux.intel.com>, Tom Murphy <murphyt7@tcd.ie>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/4] dma-iommu: pass SKIP_CPU_SYNC to swiotlb unmap
Date: Mon, 2 Aug 2021 14:54:46 +0100	[thread overview]
Message-ID: <20210802135446.GE28547@willie-the-truck> (raw)
In-Reply-To: <20210709033502.3545820-4-stevensd@google.com>

On Fri, Jul 09, 2021 at 12:35:01PM +0900, David Stevens wrote:
> From: David Stevens <stevensd@chromium.org>
> 
> If SKIP_CPU_SYNC isn't already set, then iommu_dma_unmap_(page|sg) has
> already called iommu_dma_sync_(single|sg)_for_cpu, so there is no need
> to copy from the bounce buffer again.
> 
> Signed-off-by: David Stevens <stevensd@chromium.org>
> ---
>  drivers/iommu/dma-iommu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index e79e274d2dc5..0a9a9a343e64 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -505,7 +505,8 @@ static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr,
>  	__iommu_dma_unmap(dev, dma_addr, size);
>  
>  	if (unlikely(is_swiotlb_buffer(phys)))
> -		swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> +		swiotlb_tbl_unmap_single(dev, phys, size, dir,
> +					 attrs | DMA_ATTR_SKIP_CPU_SYNC);
>  }

I think it would be cleaner to drop DMA_ATTR_SKIP_CPU_SYNC in the callers
once they've called iommu_dma_sync_*_for_cpu().

Will

  reply	other threads:[~2021-08-02 14:05 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-09  3:34 [PATCH v2 0/4] Fixes for dma-iommu swiotlb bounce buffers David Stevens
2021-07-09  3:34 ` [PATCH v2 1/4] dma-iommu: fix sync_sg with swiotlb David Stevens
2021-08-02 13:30   ` Will Deacon
2021-08-05  3:40     ` David Stevens
2021-07-09  3:35 ` [PATCH v2 2/4] dma-iommu: fix arch_sync_dma for map " David Stevens
2021-08-02 13:40   ` Will Deacon
2021-08-02 13:50     ` Will Deacon
2021-07-09  3:35 ` [PATCH v2 3/4] dma-iommu: pass SKIP_CPU_SYNC to swiotlb unmap David Stevens
2021-08-02 13:54   ` Will Deacon [this message]
2021-08-05  5:26     ` David Stevens
2021-08-06 11:38       ` Will Deacon
2021-07-09  3:35 ` [PATCH v2 4/4] dma-iommu: Check CONFIG_SWIOTLB more broadly David Stevens

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