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From: Arnd Bergmann <arnd@arndb.de>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
	"Tomasz Stanislawski" <t.stanislaws@samsung.com>,
	k.debski@samsung.com, kgene.kim@samsung.com,
	kyungmin.park@samsung.com,
	"Sylwester Nawrocki" <s.nawrocki@samsung.com>,
	"Andrzej Pietrasiewicz" <andrzej.p@samsung.com>,
	" '대인기'" <inki.dae@samsung.com>, " '강민규'" <mk7.kang@samsung.com>,
	"'KyongHo Cho'" <pullip.cho@samsung.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/7] ARM: Samsung: update/rewrite Samsung SYSMMU (IOMMU) driver
Date: Fri, 11 Mar 2011 17:00:17 +0100	[thread overview]
Message-ID: <201103111700.17373.arnd@arndb.de> (raw)
In-Reply-To: <000201cbe002$768d9de0$63a8d9a0$%szyprowski@samsung.com>

On Friday 11 March 2011, Marek Szyprowski wrote:
> > > > does not support IOMMUs, but that could be changed by wrapping it
> > > > using the include/asm-generic/dma-mapping-common.h infrastructure.
> > >
> > > ARM dma-mapping framework also requires some additional research for better DMA
> > > support (there are still issues with multiple mappings to be resolved).
> > 
> > You mean mapping the same memory into multiple devices, or a different problem?
> 
> Mapping the same memory area multiple times with different cache settings is not
> legal on ARMv7+ systems. Currently the problems might caused by the low-memory
> kernel linear mapping and second mapping created for example by dma_alloc_coherent()
> function.

Yes, I know this problem, but I don't think the case you describe is a serious
limitation (there are more interesting cases, though): dma_map_single() etc
will create additional *bus* addresses for a physical address, not additional
virtual addresses.

dma_alloc_coherent should allocate memory that is not also mapped cached,
which is what I thought we do correctly.

	Arnd

  reply	other threads:[~2011-03-11 16:00 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-03-04  9:01 [PATCH/RFC 0/7] Samsung IOMMU videobuf2 allocator and s5p-fimc update Marek Szyprowski
2011-03-04  9:01 ` [PATCH 1/7] ARM: S5PV310: Add platform definitions for FIMC Marek Szyprowski
2011-03-12  0:27   ` Kukjin Kim
2011-03-04  9:01 ` [PATCH 2/7] ARM: S5PV310: power domains: fixes and code cleanup Marek Szyprowski
2011-03-04  9:01 ` [PATCH 3/7] ARM: Samsung: update/rewrite Samsung SYSMMU (IOMMU) driver Marek Szyprowski
2011-03-04 16:04   ` Marek Szyprowski
2011-03-10 14:52     ` Arnd Bergmann
2011-03-11  9:04       ` Marek Szyprowski
2011-03-11 11:50         ` Arnd Bergmann
2011-03-11 12:35           ` Marek Szyprowski
2011-03-11 14:07             ` Arnd Bergmann
2011-03-11 14:51               ` Marek Szyprowski
2011-03-11 15:15                 ` Arnd Bergmann
2011-03-11 15:39                   ` Marek Szyprowski
2011-03-11 16:00                     ` Arnd Bergmann [this message]
2011-03-14 12:37                       ` KyongHo Cho
2011-03-14 12:46                         ` Russell King - ARM Linux
2011-03-15  1:45                           ` InKi Dae
2011-03-15  8:35                             ` Russell King - ARM Linux
2011-03-15  9:34                               ` daeinki
2011-03-15  9:53                                 ` Russell King - ARM Linux
2011-03-14 13:32                         ` Arnd Bergmann
2011-03-04  9:01 ` [PATCH 4/7] v4l: videobuf2: add Samsung SYSMMU (IOMMU) based allocator Marek Szyprowski
2011-03-04  9:01 ` [PATCH 5/7] s5p-fimc: add pm_runtime support Marek Szyprowski
2011-03-04  9:01 ` [PATCH 6/7] s5p-fimc: Add support for vb2-s5p-iommu allocator Marek Szyprowski
2011-03-04  9:01 ` [PATCH 7/7] ARM: S5PC210: enable FIMC on Universal_C210 Marek Szyprowski
2011-03-08  7:28 ` [PATCH/RFC 0/7] Samsung IOMMU videobuf2 allocator and s5p-fimc update Kukjin Kim
2011-03-08  9:34   ` Marek Szyprowski
2011-03-08 10:05     ` InKi Dae

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