iommu/arm-smmu: Don't allocate resources for bypass domains

Until we get fully plumbed into of_iommu_configure, our default
IOMMU_DOMAIN_DMA domains just bypass translation. Since we achieve that
by leaving the stream table entries set to bypass instead of pointing at
a translation context, the context bank we allocate for the domain is
completely wasted. Context banks are typically a rather limited
resource, so don't hog ones we don't need.

Reported-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 5158febd889d..7c39ac4b9c53 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -826,6 +826,12 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
         if (smmu_domain->smmu)
                 goto out_unlock;
 
+        /* We're bypassing these SIDs, so don't allocate an actual context */
+        if (domain->type == IOMMU_DOMAIN_DMA) {
+                smmu_domain->smmu = smmu;
+                goto out_unlock;
+        }
+
         /*
          * Mapping the requested stage onto what we support is surprisingly
          * complicated, mainly because the spec allows S1+S2 SMMUs without
@@ -948,7 +954,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
         void __iomem *cb_base;
         int irq;
 
-        if (!smmu)
+        if (!smmu || domain->type == IOMMU_DOMAIN_DMA)
                 return;
 
         /*