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Groups > linux.kernel > #1682460
| From | Arnd Bergmann <arnd@arndb.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols |
| Date | 2017-07-06 16:10 +0200 |
| Message-ID | <u0fDH-5sz-9@gated-at.bofh.it> (permalink) |
| References | (7 earlier) <u0aun-1Sl-33@gated-at.bofh.it> <u0aE2-1W0-15@gated-at.bofh.it> <u0e4X-4gf-43@gated-at.bofh.it> <u0faG-4Uc-19@gated-at.bofh.it> <u0fkl-4Ys-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, Jul 6, 2017 at 3:49 PM, Tomasz Figa <tfiga@chromium.org> wrote:
> On Thu, Jul 6, 2017 at 10:31 PM, Tomasz Figa <tfiga@chromium.org> wrote:
>> On the other hand, if it's strictly about base/dma-mapping, we might
>> not need it indeed. The driver could call iommu-dma helpers directly,
>> without the need to provide its own DMA ops. One caveat, though, we
>> are not able to obtain coherent (i.e. uncached) memory with this
>> approach, which might have some performance effects and complicates
>> the code, that would now need to flush caches even for some small
>> internal buffers.
>
> I think I should add a bit of explanation here:
> 1) the device is non-coherent with CPU caches, even on x86,
> 2) it looks like x86 does not have non-coherent DMA ops, (but it
> might be something that could be fixed)
I don't understand what this means here. The PCI on x86 is always
cache-coherent, so why is the device not?
Do you mean that the device has its own caches that may need
flushing to make the device cache coherent with the CPU cache,
rather than flushing the CPU caches?
Arnd
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[RFC PATCH 0/5] Fixes for loadable modules implementing DMA/IOMMU APIs Tomasz Figa <tfiga@chromium.org> - 2017-07-05 09:20 +0200
[RFC PATCH 5/5] iommu/dma: Add iommu_dma_cleanup() Tomasz Figa <tfiga@chromium.org> - 2017-07-05 09:20 +0200
[RFC PATCH 2/5] base: dma-mapping: Provide a function to look up remapped pages Tomasz Figa <tfiga@chromium.org> - 2017-07-05 09:20 +0200
[RFC PATCH 3/5] iommu: Export non-static functions to use in modules Tomasz Figa <tfiga@chromium.org> - 2017-07-05 09:20 +0200
[RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-05 09:20 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Christoph Hellwig <hch@lst.de> - 2017-07-05 17:20 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-05 17:30 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Christoph Hellwig <hch@lst.de> - 2017-07-05 19:30 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-06 03:50 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Arnd Bergmann <arnd@arndb.de> - 2017-07-06 10:30 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-06 10:40 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-06 10:50 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Arnd Bergmann <arnd@arndb.de> - 2017-07-06 14:30 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-06 15:40 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-06 15:50 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-06 16:10 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Arnd Bergmann <arnd@arndb.de> - 2017-07-06 16:30 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Tomasz Figa <tfiga@chromium.org> - 2017-07-06 16:40 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Arnd Bergmann <arnd@arndb.de> - 2017-07-06 16:10 +0200
Re: [RFC PATCH 1/5] base: dma-mapping: Export commonly used symbols Arnd Bergmann <arnd@arndb.de> - 2017-07-06 16:00 +0200
[RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Tomasz Figa <tfiga@chromium.org> - 2017-07-05 09:20 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Robin Murphy <robin.murphy@arm.com> - 2017-07-05 18:30 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Tomasz Figa <tfiga@chromium.org> - 2017-07-06 04:30 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Robin Murphy <robin.murphy@arm.com> - 2017-07-06 13:20 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Christoph Hellwig <hch@lst.de> - 2017-07-06 16:20 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Tomasz Figa <tfiga@chromium.org> - 2017-07-06 16:20 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Tomasz Figa <tfiga@chromium.org> - 2017-07-06 16:30 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Arnd Bergmann <arnd@arndb.de> - 2017-07-06 16:40 +0200
Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules Tomasz Figa <tfiga@chromium.org> - 2017-07-06 16:50 +0200
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