Re: [PATCH 1/2] arm: msm: Add System MMU support.

[Stepan Moskovchenko]

 On 8/3/2010 2:23 AM, Roedel, Joerg wrote:
> On Mon, Aug 02, 2010 at 04:29:38PM -0400, Zach Pfeffer wrote:
> > On Mon, Aug 02, 2010 at 09:58:02AM +0200, Roedel, Joerg wrote:
> > > In the means of the IOMMU-API the domain is the abstraction of an
> > > address space (in other words a page table). The IOMMU(s) which this domain
> > > is later assigned to are determined by the iommu_attach_device calls.
> > > I think the right way to go here is to create the concept of a
> > > device-context in the IOMMU-API and add functions like
> > >
> > > 	iommu_attach_context(struct iommu_domain *domain,
> > > 			     struct iommu_context *ctxt);
> > > 	iommu_detach_context(struct iommu_context *ctxt);
> > >
> > > This would work if you can determine in your iommu-driver which iommu
> > > you need to program for which device. What do you think?
> > Joerg, I'd like to make sure I understand this. A domain is an address
> > space separate from the actual page-tables that may be part of an
> > iommu_context, correct? After I iommu_attach_context the ctxt will
> > reflect the address space of the domain, correct?
> A domain is defined by a single page-table which can be modified using
> the iommu_map/iommu_unmap function calls. I am not completly sure what
> you mean by an iommu_context. Can you describe what it means in your
> context?
>
> 	Joerg

Joerg,
I think with some rework, all my use cases can be handled by your 
existing iommu API. If the domain is treated basically a page table, 
there will be some changes, but I think it can be done. I will push a 
new version of my driver in a few days.

One thing that may be helpful for the future, however, is maybe 
something like adding iommu_tlb_flush to the ops. I suppose this would 
either have to take a device, or the domain would need to keep a list of 
devices it had been attached to (so that their TLBs can be invalidated). 
But I suppose on the other hand, iommu_map/unmap may be able to just 
implicitly invalidate the TLB also, since TLB invalidation often follows 
map/unmap. What are your thoughts?

Thanks
Steve
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