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Date:   Tue, 5 Feb 2019 17:38:37 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Thierry Reding <thierry.reding@gmail.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dma-direct: Export dma_direct_alloc() and
 dma_direct_free()
Message-ID: <20190205163837.GA1222@lst.de>
References: <20190205110602.27717-1-thierry.reding@gmail.com> <20190205161036.GA782@lst.de> <20190205162057.GA29974@ulmo>
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On Tue, Feb 05, 2019 at 05:20:57PM +0100, Thierry Reding wrote:
> The problem is that if I use dma_alloc_coherent(), then the memory will
> already be mapped via the SMMU at that point and then the driver, not
> knowing that memory has already been mapped, will attempt to map an IOVA
> which will cause an SMMU fault when the host1x tries to access the
> memory.
> 
> I didn't find an equivalent to arm_iommu_detach_device() for non-ARM,
> but then stumbled across this and thought it was rather convenient for
> these cases. If there's a better way to deal with this situation, I'd be
> happy to do so.

So you basically do a dma_direct_alloc + iommu_map?  Can you send me
a pointer to your code?  Maybe we need to add a proper IOMMU-layer
API for that.