On Tue, Jan 24, 2012 at 03:46:01PM +0200, Felipe Balbi wrote:

On Tue, Jan 24, 2012 at 02:41:21PM +0100, Hiroshi Doyu wrote:

quoted

Actually I really like the concept of this "domain" now, which hides
the H/W hierarchy from users.

But in Tegra SMMU/GART case, there's a single one IOMMU device in the
system. Keeping a iommu device list in a domain and iterating iommu
device list in each iommu_ops seem to be so nice, but I'm afraid that
this may be a bit too much when one already knows that there's only
one IOMMU device in the system.

If there's no actual problem for 1-1 mapping between IOMMU H/Ws and
domains, I think that it may not so bad to keep the original code(1-1)
for GART and SMMU. What do you think?

I think it boils down to "extensability". If you can truly/fully
guarantee that there will *always* be a single IOMMU on all upcoming
Tegras, then it's really overkill.

But if there's even a remote possibility of the HW being changed and you
end up with more IOMMUs, things start to feel necessary for the sake of
making it easy to extend.

Right. But I am fine with the logic as-is when there is only one SMMU in
the system. But please also change the IOMMU driver so that it really
only initializes a single SMMU. When boards pop up with more than one
you we notice that assumption in the code again and are reminded to
change it.


	Joerg