[PATCH v4 0/4] arm64: IOMMU-backed DMA mapping

Will Deacon will.deacon at arm.com
Tue Jul 28 05:46:57 PDT 2015

Hi Joerg, Robin,

On Mon, Jul 20, 2015 at 06:23:35PM +0100, Robin Murphy wrote:
> On 20/07/15 16:26, Joerg Roedel wrote:
> > On Thu, Jul 16, 2015 at 07:40:11PM +0100, Robin Murphy wrote:
> >>   arch/arm64/Kconfig                   |   1 +
> >>   arch/arm64/include/asm/dma-mapping.h |  15 +-
> >>   arch/arm64/mm/dma-mapping.c          | 452 +++++++++++++++++++++++++++++
> >
> > What happened to the plan to merge this with the existing iommu-based
> > dma-api implementation for 32 bit ARM?
> The issue currently is that there are a bunch of drivers using the 
> exported arm_iommu_* functions directly. From what I can tell, they seem 
> like they could probably all be converted to using default domains 
> and/or the new domain type abstractions via the core IOMMU API, which 
> would then allow killing off dma_iommu_mapping and rewriting the 
> arch/arm implementation to use the new shared code. I don't currently 
> have any 32-bit platform to test with, so I'm a little dubious of taking 
> that all on myself right now.
> In the meantime on arm64, DMA mapping ops are needed for SMMUv3 platform 
> device support, the Mediatek M4U patches and my own SMMUv2 work, so it 
> would be very useful to get the arm64 and common code in as a first 
> step, then look at cleaning up arch/arm for 4.4 without dangling 
> dependencies.

What's the plan with this? Do we need to port 32-bit ARM before it's a
candidate for merging, or can we push ahead with getting this up and
running for arm64 (which currently can't use an IOMMU for DMA)?


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