Re: [GIT PULL] iommu/arm-smmu: Fixes for 4.9

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

Hi Joerg,

On Thu, Nov 03, 2016 at 09:33:04AM -0600, Joerg Roedel wrote:
> On Fri, Oct 28, 2016 at 05:01:48PM +0100, Will Deacon wrote:
> >       iommu/arm-smmu: Don't inadvertently reject multiple SMMUv3s
> 
> Hmm, this patch is pretty ugly. Wouldn't it be better to have
> hardware-independent init-routine in the arm-smmu-v3 driver that checks
> DT whether there is an SMMU at all and if yes, sets the per-bus
> iommu-ops?

We're basically doing that already, since the bus_set_iommu call happens in
the probe routine, which won't run unless an SMMUv3 has been found in the
DT. The issue we're trying to avoid is failing the probe of a second SMMUv3
in the system, because the bus will already have the iommu ops set by the
first SMMUv3 that probed.

I suppose we could go and compare bus->iommu_ops with &arm_smmu_ops, but
given that we can't support different IOMMU types on a single bus, I don't
think we gain anything from that.

Will