On Wed, Feb 1, 2017 at 10:23 AM, Rob Clark <robdclark@xxxxxxxxx> wrote:
> Before the driver is probed, arm_smmu_add_device() helpfully attaches
> an IOMMU_DOMAIN_DMA domain. Which ofc does not support stalling, and
> when the driver later attaches a domain that can_stall to an smmu that
> can stall, the default _DMA domain prevents stalling from being enabled.
> (And will cause further problems later)
>
> One simple way to deal with this is simply toss the default _DMA domain
> if the driver attaches it's own domain.
>
> TODO maybe the tracking of list of attached domains should be done in
> iommu core, so the detach can happen outside of group->mutex.
>
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxx>
> ---
> drivers/iommu/arm-smmu.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 96a1be6..50bf135 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1323,6 +1323,21 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>
> smmu = fwspec_smmu(fwspec);
>
> + /*
> + * If driver is explicitly managing the iommu, detatch any previously
> + * attached _DMA domains.
> + *
> + * TODO maybe this logic should be in iommu_attach_device() so it can
> + * happen outside of holding group->mutex??
> + */
> + if (domain->type != IOMMU_DOMAIN_DMA) {
> + struct arm_smmu_domain *other_domain, *n;
> +
> + list_for_each_entry_safe(other_domain, n, &smmu->domain_list, domain_node)
> + if (other_domain->domain.type == IOMMU_DOMAIN_DMA)
> + arm_smmu_detach_dev(&other_domain->domain, dev);
hmm, we might want to unhook dev->archdata.dma_ops here too..
I'm thinking maybe on arm64 __generic_dma_ops() should fall back to
swiotlb ops instead of dummy_ops if archdata.dma_ops is NULL, so that
we could just set it to NULL here?
(Is there really any purpose for having the dummy-ops??)
BR,
-R
> + }
> +
> if (WARN_ON(!list_empty(&smmu_domain->domain_node)))
> return -EINVAL;
>
> --
> 2.9.3
>
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