From: Russell King - ARM Linux <linux@arm.linux.org.uk> To: Arnd Bergmann <arnd@arndb.de> Cc: linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC] ARM DMA mapping TODO, v1 Date: Wed, 27 Apr 2011 08:35:14 +0100 [thread overview] Message-ID: <20110427073514.GH17290@n2100.arm.linux.org.uk> (raw) In-Reply-To: <201104212129.17013.arnd@arndb.de> On Thu, Apr 21, 2011 at 09:29:16PM +0200, Arnd Bergmann wrote: > 1. Fix the arm version of dma_alloc_coherent. It's in use today and > is broken on modern CPUs because it results in both cached and > uncached mappings. Rebecca suggested different approaches how to > get there. I also suggested various approaches and produced patches, which I'm slowly feeding in. However, I think whatever we do, we'll end up breaking something along the line - especially as various places assume that dma_alloc_coherent() is ultimately backed by memory with a struct page. > 2. Implement dma_alloc_noncoherent on ARM. Marek pointed out > that this is needed, and it currently is not implemented, with > an outdated comment explaining why it used to not be possible > to do it. dma_alloc_noncoherent is an entirely pointless API afaics. > 3. Convert ARM to use asm-generic/dma-mapping-common.h. We need > both IOMMU and direct mapped DMA on some machines. > > 4. Implement an architecture independent version of dma_map_ops > based on the iommu.h API. As Joerg mentioned, this has been > missing for some time, and it would be better to do it once > than for each IOMMU separately. This is probably a lot of work. dma_map_ops design is broken - we can't have the entire DMA API indirected through that structure. Whether you have an IOMMU or not is completely independent of whether you have to do DMA cache handling. Moreover, with dmabounce, having the DMA cache handling in place doesn't make sense. So you can't have a dma_map_ops for the cache handling bits, a dma_map_ops for IOMMU, and a dma_map_ops for the dmabounce stuff. It just doesn't work like that. I believe the dma_map_ops stuff in asm-generic to be entirely unsuitable for ARM.
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From: linux@arm.linux.org.uk (Russell King - ARM Linux) To: linux-arm-kernel@lists.infradead.org Subject: [RFC] ARM DMA mapping TODO, v1 Date: Wed, 27 Apr 2011 08:35:14 +0100 [thread overview] Message-ID: <20110427073514.GH17290@n2100.arm.linux.org.uk> (raw) In-Reply-To: <201104212129.17013.arnd@arndb.de> On Thu, Apr 21, 2011 at 09:29:16PM +0200, Arnd Bergmann wrote: > 1. Fix the arm version of dma_alloc_coherent. It's in use today and > is broken on modern CPUs because it results in both cached and > uncached mappings. Rebecca suggested different approaches how to > get there. I also suggested various approaches and produced patches, which I'm slowly feeding in. However, I think whatever we do, we'll end up breaking something along the line - especially as various places assume that dma_alloc_coherent() is ultimately backed by memory with a struct page. > 2. Implement dma_alloc_noncoherent on ARM. Marek pointed out > that this is needed, and it currently is not implemented, with > an outdated comment explaining why it used to not be possible > to do it. dma_alloc_noncoherent is an entirely pointless API afaics. > 3. Convert ARM to use asm-generic/dma-mapping-common.h. We need > both IOMMU and direct mapped DMA on some machines. > > 4. Implement an architecture independent version of dma_map_ops > based on the iommu.h API. As Joerg mentioned, this has been > missing for some time, and it would be better to do it once > than for each IOMMU separately. This is probably a lot of work. dma_map_ops design is broken - we can't have the entire DMA API indirected through that structure. Whether you have an IOMMU or not is completely independent of whether you have to do DMA cache handling. Moreover, with dmabounce, having the DMA cache handling in place doesn't make sense. So you can't have a dma_map_ops for the cache handling bits, a dma_map_ops for IOMMU, and a dma_map_ops for the dmabounce stuff. It just doesn't work like that. I believe the dma_map_ops stuff in asm-generic to be entirely unsuitable for ARM.
next prev parent reply other threads:[~2011-04-27 8:03 UTC|newest] Thread overview: 196+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-04-21 19:29 [RFC] ARM DMA mapping TODO, v1 Arnd Bergmann 2011-04-21 19:29 ` Arnd Bergmann 2011-04-21 20:09 ` [Linaro-mm-sig] " Jesse Barnes 2011-04-21 20:09 ` Jesse Barnes 2011-04-21 21:52 ` Zach Pfeffer 2011-04-21 21:52 ` Zach Pfeffer 2011-04-22 0:34 ` KyongHo Cho 2011-04-22 0:34 ` KyongHo Cho 2011-04-26 14:29 ` Arnd Bergmann 2011-04-26 14:29 ` Arnd Bergmann 2011-04-26 14:28 ` Arnd Bergmann 2011-04-26 14:28 ` Arnd Bergmann 2011-04-26 14:26 ` Arnd Bergmann 2011-04-26 14:26 ` Arnd Bergmann 2011-04-26 15:39 ` Jesse Barnes 2011-04-26 15:39 ` Jesse Barnes 2011-04-27 7:35 ` Russell King - ARM Linux [this message] 2011-04-27 7:35 ` Russell King - ARM Linux 2011-04-27 8:56 ` Arnd Bergmann 2011-04-27 8:56 ` Arnd Bergmann 2011-04-27 9:09 ` Russell King - ARM Linux 2011-04-27 9:09 ` Russell King - ARM Linux 2011-04-27 11:02 ` Arnd Bergmann 2011-04-27 11:02 ` Arnd Bergmann 2011-04-27 16:16 ` [Linaro-mm-sig] " Alex Deucher 2011-04-27 16:16 ` Alex Deucher 2011-04-27 17:44 ` Anca Emanuel 2011-04-27 17:44 ` Anca Emanuel 2011-04-27 20:27 ` Russell King - ARM Linux 2011-04-27 20:27 ` Russell King - ARM Linux 2011-04-27 20:16 ` Russell King - ARM Linux 2011-04-27 20:16 ` Russell King - ARM Linux 2011-04-27 20:21 ` Arnd Bergmann 2011-04-27 20:21 ` Arnd Bergmann 2011-04-27 20:26 ` Russell King - ARM Linux 2011-04-27 20:26 ` Russell King - ARM Linux 2011-04-27 20:48 ` Arnd Bergmann 2011-04-27 20:48 ` Arnd Bergmann 2011-04-27 21:41 ` Benjamin Herrenschmidt 2011-04-27 21:41 ` Benjamin Herrenschmidt 2011-04-28 9:30 ` Russell King - ARM Linux 2011-04-28 9:30 ` Russell King - ARM Linux 2011-04-28 21:07 ` Benjamin Herrenschmidt 2011-04-28 21:07 ` Benjamin Herrenschmidt 2011-04-29 11:26 ` Arnd Bergmann 2011-04-29 11:26 ` Arnd Bergmann 2011-04-29 11:47 ` Benjamin Herrenschmidt 2011-04-29 11:47 ` Benjamin Herrenschmidt 2011-04-29 11:56 ` Alan Cox 2011-04-29 11:56 ` Alan Cox 2011-04-29 22:51 ` Benjamin Herrenschmidt 2011-04-29 22:51 ` Benjamin Herrenschmidt 2011-04-29 12:06 ` [Linaro-mm-sig] " Thomas Hellstrom 2011-04-29 12:06 ` Thomas Hellstrom 2011-04-29 13:34 ` Jerome Glisse 2011-04-29 13:34 ` Jerome Glisse 2011-04-29 22:55 ` Benjamin Herrenschmidt 2011-04-29 22:55 ` Benjamin Herrenschmidt 2011-04-29 22:53 ` Benjamin Herrenschmidt 2011-04-29 22:53 ` Benjamin Herrenschmidt 2011-04-27 10:51 ` Marek Szyprowski 2011-04-27 10:51 ` Marek Szyprowski 2011-04-27 21:37 ` Benjamin Herrenschmidt 2011-04-27 21:37 ` Benjamin Herrenschmidt 2011-04-28 6:40 ` [Linaro-mm-sig] " Arnd Bergmann 2011-04-28 6:40 ` Arnd Bergmann 2011-04-28 6:46 ` FUJITA Tomonori 2011-04-28 6:46 ` FUJITA Tomonori 2011-04-28 9:37 ` Russell King - ARM Linux 2011-04-28 9:37 ` Russell King - ARM Linux 2011-04-28 10:32 ` [Linaro-mm-sig] " Marek Szyprowski 2011-04-28 10:32 ` Marek Szyprowski 2011-04-28 10:51 ` Russell King - ARM Linux 2011-04-28 10:51 ` Russell King - ARM Linux 2011-04-28 12:28 ` Arnd Bergmann 2011-04-28 12:28 ` Arnd Bergmann 2011-04-28 13:15 ` Russell King - ARM Linux 2011-04-28 13:15 ` Russell King - ARM Linux 2011-04-28 14:29 ` Arnd Bergmann 2011-04-28 14:29 ` Arnd Bergmann 2011-04-28 14:34 ` Russell King - ARM Linux 2011-04-28 14:34 ` Russell King - ARM Linux 2011-04-28 14:39 ` Arnd Bergmann 2011-04-28 14:39 ` Arnd Bergmann 2011-04-28 14:58 ` Russell King - ARM Linux 2011-04-28 14:58 ` Russell King - ARM Linux 2011-04-28 19:37 ` Jerome Glisse 2011-04-28 19:37 ` Jerome Glisse 2011-04-29 0:29 ` Benjamin Herrenschmidt 2011-04-29 0:29 ` Benjamin Herrenschmidt 2011-04-29 5:50 ` Thomas Hellstrom 2011-04-29 5:50 ` Thomas Hellstrom 2011-04-29 7:35 ` Benjamin Herrenschmidt 2011-04-29 7:35 ` Benjamin Herrenschmidt 2011-04-29 10:55 ` Thomas Hellstrom 2011-04-29 10:55 ` Thomas Hellstrom 2011-04-29 22:50 ` Benjamin Herrenschmidt 2011-04-29 22:50 ` Benjamin Herrenschmidt 2011-04-29 16:27 ` Jesse Barnes 2011-04-29 16:27 ` Jesse Barnes 2011-04-29 22:46 ` Benjamin Herrenschmidt 2011-04-29 22:46 ` Benjamin Herrenschmidt 2011-04-30 2:45 ` Jesse Barnes 2011-04-30 2:45 ` Jesse Barnes 2011-04-29 7:59 ` Russell King - ARM Linux 2011-04-29 7:59 ` Russell King - ARM Linux 2011-04-29 16:32 ` Jesse Barnes 2011-04-29 16:32 ` Jesse Barnes 2011-04-29 18:29 ` Arnd Bergmann 2011-04-29 18:29 ` Arnd Bergmann 2011-04-29 22:15 ` Russell King - ARM Linux 2011-04-29 22:15 ` Russell King - ARM Linux 2011-05-02 4:42 ` David Brown 2011-05-02 4:42 ` David Brown 2011-05-02 11:26 ` Arnd Bergmann 2011-05-02 11:26 ` Arnd Bergmann 2011-04-29 22:37 ` Benjamin Herrenschmidt 2011-04-29 22:37 ` Benjamin Herrenschmidt 2011-04-29 13:42 ` Joerg Roedel 2011-04-29 13:42 ` Joerg Roedel 2011-04-29 14:19 ` Jerome Glisse 2011-04-29 14:19 ` Jerome Glisse 2011-04-29 15:37 ` Jordan Crouse 2011-04-29 15:37 ` Jordan Crouse 2011-04-28 14:38 ` FUJITA Tomonori 2011-04-28 14:38 ` FUJITA Tomonori 2011-04-29 0:25 ` Benjamin Herrenschmidt 2011-04-29 0:25 ` Benjamin Herrenschmidt 2011-04-29 11:21 ` Arnd Bergmann 2011-04-29 11:21 ` Arnd Bergmann 2011-04-28 10:41 ` Joerg Roedel 2011-04-28 10:41 ` Joerg Roedel 2011-04-28 11:01 ` Russell King - ARM Linux 2011-04-28 11:01 ` Russell King - ARM Linux 2011-04-28 12:25 ` Joerg Roedel 2011-04-28 12:25 ` Joerg Roedel 2011-04-28 12:42 ` Russell King - ARM Linux 2011-04-28 12:42 ` Russell King - ARM Linux 2011-04-28 12:59 ` Joerg Roedel 2011-04-28 12:59 ` Joerg Roedel 2011-04-28 13:02 ` Arnd Bergmann 2011-04-28 13:02 ` Arnd Bergmann 2011-04-28 13:19 ` Russell King - ARM Linux 2011-04-28 13:19 ` Russell King - ARM Linux 2011-04-28 13:56 ` Joerg Roedel 2011-04-28 13:56 ` Joerg Roedel 2011-04-28 14:30 ` Russell King - ARM Linux 2011-04-28 14:30 ` Russell King - ARM Linux 2011-04-27 9:52 ` Catalin Marinas 2011-04-27 9:52 ` Catalin Marinas 2011-04-27 10:43 ` Arnd Bergmann 2011-04-27 10:43 ` Arnd Bergmann 2011-04-27 11:08 ` Catalin Marinas 2011-04-27 11:08 ` Catalin Marinas 2011-04-28 0:15 ` Valdis.Kletnieks 2011-04-28 0:15 ` Valdis.Kletnieks at vt.edu 2011-04-28 8:27 ` Catalin Marinas 2011-04-28 8:27 ` Catalin Marinas 2011-04-28 12:12 ` Arnd Bergmann 2011-04-28 12:12 ` Arnd Bergmann 2011-04-28 12:36 ` Russell King - ARM Linux 2011-04-28 12:36 ` Russell King - ARM Linux 2011-04-28 12:48 ` Arnd Bergmann 2011-04-28 12:48 ` Arnd Bergmann 2011-05-03 14:45 ` Dave Martin 2011-05-03 14:45 ` Dave Martin 2011-04-29 15:41 ` [Linaro-mm-sig] " Arnd Bergmann 2011-04-29 15:41 ` Arnd Bergmann 2011-04-29 16:42 ` Catalin Marinas 2011-04-29 16:42 ` Catalin Marinas 2011-05-03 15:05 ` [Linaro-mm-sig] " Laurent Pinchart 2011-05-03 15:05 ` Laurent Pinchart 2011-05-03 15:31 ` Arnd Bergmann 2011-05-03 15:31 ` Arnd Bergmann 2011-04-27 14:06 ` FUJITA Tomonori 2011-04-27 14:06 ` FUJITA Tomonori 2011-04-27 14:29 ` Catalin Marinas 2011-04-27 14:29 ` Catalin Marinas 2011-04-27 14:34 ` FUJITA Tomonori 2011-04-27 14:34 ` FUJITA Tomonori 2011-04-27 20:29 ` Russell King - ARM Linux 2011-04-27 20:29 ` Russell King - ARM Linux 2011-04-27 21:45 ` Benjamin Herrenschmidt 2011-04-27 21:45 ` Benjamin Herrenschmidt 2011-04-28 7:24 ` [Linaro-mm-sig] " KyongHo Cho 2011-04-28 7:24 ` KyongHo Cho 2011-04-28 8:31 ` Catalin Marinas 2011-04-28 8:31 ` Catalin Marinas 2011-04-27 21:31 ` Benjamin Herrenschmidt 2011-04-27 21:31 ` Benjamin Herrenschmidt 2011-04-28 9:42 ` Russell King - ARM Linux 2011-04-28 9:42 ` Russell King - ARM Linux 2011-04-28 10:27 ` Joerg Roedel 2011-04-28 10:27 ` Joerg Roedel 2011-04-28 12:15 ` Arnd Bergmann 2011-04-28 12:15 ` Arnd Bergmann
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