[PATCH v6 3/3] iommu/arm-smmu-v3: Enable CFGI/TLBI-repeat workaround on Tegra264
From: Ashish Mhetre <hidden>
Date: 2026-07-13 11:16:17
Also in:
linux-doc, linux-iommu, linux-tegra, lkml
Subsystem:
arm smmu drivers, arm64 port (aarch64 architecture), documentation, iommu subsystem, the rest · Maintainers:
Will Deacon, Catalin Marinas, Jonathan Corbet, Joerg Roedel, Linus Torvalds
Nvidia Tegra264 SMMU is affected by an erratum where a TLB entry can survive an invalidation that races with concurrent traffic targeting the same entry. The hardware-recommended software workaround is to issue every CFGI/TLBI command (each followed by CMD_SYNC) twice, and that infrastructure is already in place behind arm_smmu_erratum_repeat_tlbi_cfgi_key. Neither IDR nor IIDR flags this Tegra264-specific bug, so hardware detection is not possible. Tegra264 is device-tree-only (no ACPI/IORT support) and already has a dedicated "nvidia,tegra264-smmu" compatible, so DT-probe is the only viable detection path. Enable the workaround on instances matching the existing "nvidia,tegra264-smmu" compatible by calling static_branch_enable() on arm_smmu_erratum_repeat_tlbi_cfgi_key. Document the erratum in Documentation/arch/arm64/silicon-errata.rst. Reviewed-by: Nicolin Chen <redacted> Signed-off-by: Ashish Mhetre <redacted> --- Documentation/arch/arm64/silicon-errata.rst | 2 ++ drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 +++- 2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index 014aa1c215a1..076b3947d259 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst@@ -312,6 +312,8 @@ stable kernels. | | | T241-MPAM-4, | | | | | T241-MPAM-6 | | +----------------+-----------------+-----------------+-----------------------------+ +| NVIDIA | T264 SMMU | T264-SMMU-3 | N/A | ++----------------+-----------------+-----------------+-----------------------------+ +----------------+-----------------+-----------------+-----------------------------+ | Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 | +----------------+-----------------+-----------------+-----------------------------+
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 eb8374cfce2a..b97bbf7943ac 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c@@ -5353,8 +5353,10 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev, if (of_dma_is_coherent(dev->of_node)) smmu->features |= ARM_SMMU_FEAT_COHERENCY; - if (of_device_is_compatible(dev->of_node, "nvidia,tegra264-smmu")) + if (of_device_is_compatible(dev->of_node, "nvidia,tegra264-smmu")) { tegra_cmdqv_dt_probe(dev->of_node, smmu); + static_branch_enable(&arm_smmu_erratum_repeat_tlbi_cfgi_key); + } return ret; }
--
2.50.1