From df198b37e72c18c771d93ffbaf2176c0270505f3 Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Mon, 15 Aug 2022 16:26:50 +0100 Subject: [PATCH] iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY better Assuming that any SMMU can enforce coherency for any device is clearly nonsense. Although technically even a single SMMU instance can be wired up to only be capable of emitting coherent traffic for some of the devices it translates, it's a fairly realistic approximation that if the SMMU's pagetable walker is wired up to a coherent interconnect then all its translation units probably are too, and conversely that lack of coherent table walks implies a non-coherent system in general. Either way it's still less inaccurate than what we've been claiming so far. Signed-off-by: Robin Murphy Link: https://lore.kernel.org/r/106c9741415f0b6358c72d53ae9c78c553a2b45c.1660574547.git.robin.murphy@arm.com Signed-off-by: Joerg Roedel --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 5 ++++- drivers/iommu/arm/arm-smmu/arm-smmu.c | 9 ++++----- 2 files changed, 8 insertions(+), 6 deletions(-) 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 ab919ec..fceab59 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -1994,9 +1994,12 @@ static const struct iommu_flush_ops arm_smmu_flush_ops = { /* IOMMU API */ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap) { + struct arm_smmu_master *master = dev_iommu_priv_get(dev); + switch (cap) { case IOMMU_CAP_CACHE_COHERENCY: - return true; + /* Assume that a coherent TCU implies coherent TBUs */ + return master->smmu->features & ARM_SMMU_FEAT_COHERENCY; case IOMMU_CAP_NOEXEC: return true; default: diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c index ce036a0..8039c8b 100644 --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c @@ -1332,13 +1332,12 @@ static phys_addr_t arm_smmu_iova_to_phys(struct iommu_domain *domain, static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap) { + struct arm_smmu_master_cfg *cfg = dev_iommu_priv_get(dev); + switch (cap) { case IOMMU_CAP_CACHE_COHERENCY: - /* - * Return true here as the SMMU can always send out coherent - * requests. - */ - return true; + /* Assume that a coherent TCU implies coherent TBUs */ + return cfg->smmu->features & ARM_SMMU_FEAT_COHERENT_WALK; case IOMMU_CAP_NOEXEC: return true; default: -- 2.7.4