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From: Arnd Bergmann <arnd@arndb.de>
To: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-renesas-soc@vger.kernel.org,
        Simon Horman <horms@verge.net.au>,
        Bjorn Helgaas <bhelgaas@google.com>, fkan@apm.com,
        linux-kernel@vger.kernel.org,
        Artemi Ivanov <artemi.ivanov@cogentembedded.com>
Subject: Re: [PATCH 2/2] arm64: avoid increasing DMA masks above what hardware supports
Date: Wed, 11 Jan 2017 22:11:32 +0100
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On Wednesday, January 11, 2017 9:31:52 PM CET Nikita Yushchenko wrote:
> @@ -959,6 +990,15 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
>         if (!dev->archdata.dma_ops)
>                 dev->archdata.dma_ops = &swiotlb_dma_ops;
>  
> +       /*
> +        * Whatever the parent bus can set. A device must not set
> +        * a DMA mask larger than this.
> +        */
> +       if (enforce_range)
> +               dev->archdata.parent_dma_mask = size - 1;
> +       else
> +               dev->archdata.parent_dma_mask = DMA_BIT_MASK(64);
> +
>         dev->archdata.dma_coherent = coherent;
>         __iommu_setup_dma_ops(dev, dma_base, size, iommu);
> 

Could we just pass the mask instead of the size here?

	Arnd