[PATCH v3 6.1 3/4] iommu/arm-smmu-v3: Add explicit feature for nesting

[Easwar Hariharan]

From: Robin Murphy <robin.murphy@xxxxxxx>

commit 1d9777b9f3d55b4b6faf186ba4f1d6fb560c0523 upstream

In certain cases we may want to refuse to allow nested translation even
when both stages are implemented, so let's add an explicit feature for
nesting support which we can control in its own right. For now this
merely serves as documentation, but it means a nice convenient check
will be ready and waiting for the future nesting code.

Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
Reviewed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Link: https://lore.kernel.org/r/136c3f4a3a84cc14a5a1978ace57dfd3ed67b688.1683731256.git.robin.murphy@xxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Easwar Hariharan <eahariha@xxxxxxxxxxxxxxxxxxx>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 ++++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index aed038f7d66c..330f909a29de 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3654,6 +3654,10 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 
 	smmu->ias = max(smmu->ias, smmu->oas);
 
+	if ((smmu->features & ARM_SMMU_FEAT_TRANS_S1) &&
+	    (smmu->features & ARM_SMMU_FEAT_TRANS_S2))
+		smmu->features |= ARM_SMMU_FEAT_NESTING;
+
 	arm_smmu_device_iidr_probe(smmu);
 
 	if (arm_smmu_sva_supported(smmu))
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index d9e4357c6869..d0b207cae107 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -645,6 +645,7 @@ struct arm_smmu_device {
 #define ARM_SMMU_FEAT_BTM		(1 << 16)
 #define ARM_SMMU_FEAT_SVA		(1 << 17)
 #define ARM_SMMU_FEAT_E2H		(1 << 18)
+#define ARM_SMMU_FEAT_NESTING		(1 << 19)
 	u32				features;
 
 #define ARM_SMMU_OPT_SKIP_PREFETCH	(1 << 0)
-- 
2.25.1