From: Arnd Bergmann <arnd@arndb.de>
To: linaro-mm-sig@lists.linaro.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
"Russell King - ARM Linux" <linux@arm.linux.org.uk>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [Linaro-mm-sig] [RFC] ARM DMA mapping TODO, v1
Date: Thu, 28 Apr 2011 08:40:08 +0200 [thread overview]
Message-ID: <201104280840.09206.arnd@arndb.de> (raw)
In-Reply-To: <1303940271.2513.187.camel@pasglop>
On Wednesday 27 April 2011 23:37:51 Benjamin Herrenschmidt wrote:
> On Wed, 2011-04-27 at 08:35 +0100, Russell King - ARM Linux wrote:
> > On Thu, Apr 21, 2011 at 09:29:16PM +0200, Arnd Bergmann wrote:
> > > 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 an outdated comment explaining why it used to not be possible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.
>
> I was about to ask what the point is ... (what is the expected
> semantic ? Memory that is reachable but not necessarily cache
> coherent ?)
Drivers use this when they explicitly want to manage the caching
themselves. I think this is most interesting on big NUMA systems,
where you really want to use fast (local cached) memory and
then flush it explicitly to do dma. Very few drivers use this:
arnd@wuerfel:~/linux-2.6$ git grep dma_alloc_noncoherent drivers/
drivers/base/dma-mapping.c: vaddr = dma_alloc_noncoherent(dev, size, dma_handle, gfp);
drivers/net/au1000_eth.c: aup->vaddr = (u32)dma_alloc_noncoherent(NULL, MAX_BUF_SIZE *
drivers/net/lasi_82596.c:#define DMA_ALLOC dma_alloc_noncoherent
drivers/net/sgiseeq.c: sr = dma_alloc_noncoherent(&pdev->dev, sizeof(*sp->srings),
drivers/scsi/53c700.c: memory = dma_alloc_noncoherent(hostdata->dev, TOTAL_MEM_SIZE,
drivers/scsi/sgiwd93.c: hdata->cpu = dma_alloc_noncoherent(&pdev->dev, HPC_DMA_SIZE,
drivers/tty/serial/mpsc.c: } else if ((pi->dma_region = dma_alloc_noncoherent(pi->port.dev,
drivers/video/au1200fb.c: fbdev->fb_mem = dma_alloc_noncoherent(&dev->dev,
> > 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.
>
> Well, the dmabounce and cache handling is one implementation that's just
> on/off with parameters no ?. iommu is different implementations. So the
> ops should be for the iommu backends. The dmabounce & cache handling is
> then done by those backends based on flags you stick in struct device
> for example.
Well, what we are currently discussing is to have a common implementation
for IOMMUs that provide the generic iommu_ops that the KVM people introduced.
Once we get there, we only need a single dma_map_ops structure for all
IOMMUs.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [Linaro-mm-sig] [RFC] ARM DMA mapping TODO, v1
Date: Thu, 28 Apr 2011 08:40:08 +0200 [thread overview]
Message-ID: <201104280840.09206.arnd@arndb.de> (raw)
In-Reply-To: <1303940271.2513.187.camel@pasglop>
On Wednesday 27 April 2011 23:37:51 Benjamin Herrenschmidt wrote:
> On Wed, 2011-04-27 at 08:35 +0100, Russell King - ARM Linux wrote:
> > On Thu, Apr 21, 2011 at 09:29:16PM +0200, Arnd Bergmann wrote:
> > > 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.
>
> I was about to ask what the point is ... (what is the expected
> semantic ? Memory that is reachable but not necessarily cache
> coherent ?)
Drivers use this when they explicitly want to manage the caching
themselves. I think this is most interesting on big NUMA systems,
where you really want to use fast (local cached) memory and
then flush it explicitly to do dma. Very few drivers use this:
arnd at wuerfel:~/linux-2.6$ git grep dma_alloc_noncoherent drivers/
drivers/base/dma-mapping.c: vaddr = dma_alloc_noncoherent(dev, size, dma_handle, gfp);
drivers/net/au1000_eth.c: aup->vaddr = (u32)dma_alloc_noncoherent(NULL, MAX_BUF_SIZE *
drivers/net/lasi_82596.c:#define DMA_ALLOC dma_alloc_noncoherent
drivers/net/sgiseeq.c: sr = dma_alloc_noncoherent(&pdev->dev, sizeof(*sp->srings),
drivers/scsi/53c700.c: memory = dma_alloc_noncoherent(hostdata->dev, TOTAL_MEM_SIZE,
drivers/scsi/sgiwd93.c: hdata->cpu = dma_alloc_noncoherent(&pdev->dev, HPC_DMA_SIZE,
drivers/tty/serial/mpsc.c: } else if ((pi->dma_region = dma_alloc_noncoherent(pi->port.dev,
drivers/video/au1200fb.c: fbdev->fb_mem = dma_alloc_noncoherent(&dev->dev,
> > 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.
>
> Well, the dmabounce and cache handling is one implementation that's just
> on/off with parameters no ?. iommu is different implementations. So the
> ops should be for the iommu backends. The dmabounce & cache handling is
> then done by those backends based on flags you stick in struct device
> for example.
Well, what we are currently discussing is to have a common implementation
for IOMMUs that provide the generic iommu_ops that the KVM people introduced.
Once we get there, we only need a single dma_map_ops structure for all
IOMMUs.
Arnd
next prev parent reply other threads:[~2011-04-28 6:40 UTC|newest]
Thread overview: 198+ 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 ` Arnd Bergmann [this message]
2011-04-28 6:40 ` [Linaro-mm-sig] " 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
2011-05-03 14:35 [Linaro-mm-sig] " Laurent Pinchart
2011-05-03 14:35 ` Laurent Pinchart
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