From: Thierry Reding <thierry.reding@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: 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()
Date: Tue, 5 Feb 2019 18:56:11 +0100 [thread overview]
Message-ID: <20190205175611.GA7052@ulmo> (raw)
In-Reply-To: <20190205163837.GA1222@lst.de>
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On Tue, Feb 05, 2019 at 05:38:37PM +0100, Christoph Hellwig wrote:
> 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.
Sure, here you go:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/host1x/cdma.c#n106
Thierry
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next prev parent reply other threads:[~2019-02-05 17:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-05 11:06 [PATCH] dma-direct: Export dma_direct_alloc() and dma_direct_free() Thierry Reding
2019-02-05 16:10 ` Christoph Hellwig
2019-02-05 16:20 ` Thierry Reding
2019-02-05 16:38 ` Christoph Hellwig
2019-02-05 17:56 ` Thierry Reding [this message]
2019-02-05 18:02 ` Christoph Hellwig
2019-02-05 22:29 ` Thierry Reding
2019-02-06 6:57 ` Christoph Hellwig
2019-02-06 7:37 ` Marek Szyprowski
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