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authorJean-Philippe Brucker <jean-philippe@linaro.org>2023-03-21 13:06:00 +0300
committerWill Deacon <will@kernel.org>2023-03-27 15:22:23 +0300
commit8c153645fa402ee96ec3c2fef9db3a087b3667ac (patch)
tree42f9d6c28efa5e9291d00688bc570c32b6b777d7 /drivers/iommu/arm
parente8d018dd0257f744ca50a729e3d042cf2ec9da65 (diff)
downloadlinux-8c153645fa402ee96ec3c2fef9db3a087b3667ac.tar.xz
iommu/arm-smmu-v3: Explain why ATS stays disabled with bypass
The SMMU does not support enabling ATS for a bypass stream. Add a comment. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Link: https://lore.kernel.org/r/20230321100559.341981-1-jean-philippe@linaro.org Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'drivers/iommu/arm')
-rw-r--r--drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c7
1 files changed, 7 insertions, 0 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 f2425b0f0cd6..a8410c132f1e 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2447,6 +2447,13 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
master->domain = smmu_domain;
+ /*
+ * The SMMU does not support enabling ATS with bypass. When the STE is
+ * in bypass (STE.Config[2:0] == 0b100), ATS Translation Requests and
+ * Translated transactions are denied as though ATS is disabled for the
+ * stream (STE.EATS == 0b00), causing F_BAD_ATS_TREQ and
+ * F_TRANSL_FORBIDDEN events (IHI0070Ea 5.2 Stream Table Entry).
+ */
if (smmu_domain->stage != ARM_SMMU_DOMAIN_BYPASS)
master->ats_enabled = arm_smmu_ats_supported(master);