From: Joerg Roedel <joro@8bytes.org> To: Russell King - ARM Linux <linux@arm.linux.org.uk> Cc: Arnd Bergmann <arnd@arndb.de>, 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: Thu, 28 Apr 2011 15:56:21 +0200 [thread overview] Message-ID: <20110428135621.GE13402@8bytes.org> (raw) In-Reply-To: <20110428131928.GL17290@n2100.arm.linux.org.uk> On Thu, Apr 28, 2011 at 02:19:28PM +0100, Russell King - ARM Linux wrote: > On Thu, Apr 28, 2011 at 03:02:16PM +0200, Arnd Bergmann wrote: > You still need this same cache handling code even when you don't have > an iommu. You can reference the same code from different places. > I don't see the point in having a dma_ops level of indirection > followed by a separate iommu_ops level of indirection - it seems to me > to be a waste of code and CPU time, and I don't see why its even > necessary when there's a much simpler way to deal with it (as I > illustrated). There is no waste of code, just the opposite. Most of the dma_ops implementations that use an IOMMU today have a lot of similiarities in their code. All this code (on x86, alpha, sparc, ia64, ...) can be unified to a generic solution that fits all (by abstracting the differences between iommus into the iommu-api). So the current situation is a much bigger code waste than having this unified. The ARM platforms supporting iommu hardware will benefit from this as well. It simply doesn't make sense to have one dma_ops implementation for each iommu hardware around. Regards, Joerg
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From: joro@8bytes.org (Joerg Roedel) To: linux-arm-kernel@lists.infradead.org Subject: [RFC] ARM DMA mapping TODO, v1 Date: Thu, 28 Apr 2011 15:56:21 +0200 [thread overview] Message-ID: <20110428135621.GE13402@8bytes.org> (raw) In-Reply-To: <20110428131928.GL17290@n2100.arm.linux.org.uk> On Thu, Apr 28, 2011 at 02:19:28PM +0100, Russell King - ARM Linux wrote: > On Thu, Apr 28, 2011 at 03:02:16PM +0200, Arnd Bergmann wrote: > You still need this same cache handling code even when you don't have > an iommu. You can reference the same code from different places. > I don't see the point in having a dma_ops level of indirection > followed by a separate iommu_ops level of indirection - it seems to me > to be a waste of code and CPU time, and I don't see why its even > necessary when there's a much simpler way to deal with it (as I > illustrated). There is no waste of code, just the opposite. Most of the dma_ops implementations that use an IOMMU today have a lot of similiarities in their code. All this code (on x86, alpha, sparc, ia64, ...) can be unified to a generic solution that fits all (by abstracting the differences between iommus into the iommu-api). So the current situation is a much bigger code waste than having this unified. The ARM platforms supporting iommu hardware will benefit from this as well. It simply doesn't make sense to have one dma_ops implementation for each iommu hardware around. Regards, Joerg
next prev parent reply other threads:[~2011-04-28 13:56 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 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 [this message] 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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