From: joerg.roedel@amd•com (Joerg Roedel)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC 0/5] ARM: dma-mapping: New dma_map_ops to control IOVA more precisely
Date: Wed, 19 Sep 2012 14:50:20 +0200 [thread overview]
Message-ID: <20120919125020.GQ2505@amd.com> (raw)
In-Reply-To: <201209190759.46174.arnd@arndb.de>
On Wed, Sep 19, 2012 at 07:59:45AM +0000, Arnd Bergmann wrote:
> On Wednesday 19 September 2012, Hiroshi Doyu wrote:
> > I guess that it would work. Originally I thought that using DMA-API
> > and IOMMU-API together in driver might be kind of layering violation
> > since IOMMU-API itself is used in DMA-API. Only DMA-API used in driver
> > might be cleaner. Considering that DMA API traditionally handling
> > anonymous {bus,iova} address only, introducing the concept of
> > specific address in DMA API may not be so encouraged, though.
> >
> > It would be nice to listen how other SoCs have solved similar needs.
>
> In general, I would recommend using only the IOMMU API when you have a device
> driver that needs to control the bus virtual address space and that manages
> a device that resides in its own IOMMU context. I would recommend using
> only the dma-mapping API when you have a device that lives in a shared
> bus virtual address space with other devices, and then never ask for
> a specific bus virtual address.
>
> Can you explain what devices you see that don't fit in one of those two
> categories?
Well, I don't think that a driver should limit to one of these 2 APIs. A
driver can very well use the IOMMU-API during initialization (for
example to map the firmware to an address the device expects it to be)
and use the DMA-API later during normal operation to exchange data with
the device.
When a device driver would only use the IOMMU-API and needs small
DMA-able areas it has to re-implement something like the DMA-API
(basically an address allocator) for that. So I don't see a reason why
both can't be used in a device driver.
Regards,
Joerg
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Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
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next prev parent reply other threads:[~2012-09-19 12:50 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-29 6:55 [RFC 0/5] ARM: dma-mapping: New dma_map_ops to control IOVA more precisely Hiroshi Doyu
2012-08-29 6:55 ` [RFC 1/5] ARM: dma-mapping: New dma_map_ops->iova_get_free_{total, max} functions Hiroshi Doyu
2012-08-29 6:55 ` [RFC 2/5] ARM: dma-mapping: New dma_map_ops->iova_{alloc, free}() functions Hiroshi Doyu
2012-08-29 6:55 ` [RFC 3/5] ARM: dma-mapping: New dma_map_ops->iova_alloc*_at* function Hiroshi Doyu
2012-08-29 6:55 ` [RFC 4/5] ARM: dma-mapping: New dma_map_ops->map_page*_at* function Hiroshi Doyu
2012-08-29 6:55 ` [RFC 5/5] ARM: dma-mapping: Introduce dma_map_linear_attrs() for IOVA linear map Hiroshi Doyu
2012-09-18 12:49 ` [RFC 0/5] ARM: dma-mapping: New dma_map_ops to control IOVA more precisely Joerg Roedel
2012-09-19 6:58 ` Hiroshi Doyu
2012-09-19 7:59 ` Arnd Bergmann
2012-09-19 11:41 ` Hiroshi Doyu
2012-09-19 12:50 ` Joerg Roedel [this message]
2012-09-20 1:44 ` Krishna Reddy
2012-09-20 2:21 ` Stephen Warren
2012-09-20 6:40 ` Krishna Reddy
2012-09-20 15:27 ` Stephen Warren
2012-09-21 18:16 ` Krishna Reddy
2012-09-24 9:04 ` How to specify IOMMU'able devices in DT (was: [RFC 0/5] ARM: dma-mapping: New dma_map_ops to control IOVA more precisely) Hiroshi Doyu
2012-09-24 9:28 ` James Bottomley
2012-09-24 9:44 ` Hiroshi Doyu
2012-09-24 11:14 ` Marek Szyprowski
2012-09-24 11:50 ` How to specify IOMMU'able devices in DT Hiroshi Doyu
2012-11-28 13:48 ` [PATCH 1/1] ARM: tegra: bus_notifier registers IOMMU devices(was: How to specify IOMMU'able devices in DT) Hiroshi Doyu
2012-11-28 18:07 ` Stephen Warren
2012-11-29 6:45 ` Hiroshi Doyu
2012-11-29 10:17 ` Thierry Reding
2012-11-30 4:59 ` Mark Zhang
2012-11-30 8:06 ` [PATCH 1/1] ARM: tegra: bus_notifier registers IOMMU devices Hiroshi Doyu
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