From: Nicolin Chen <nicolinc@nvidia•com>
To: Ashish Mhetre <amhetre@nvidia•com>
Cc: <will@kernel•org>, <robin.murphy@arm•com>, <joro@8bytes•org>,
<jgg@ziepe•ca>, <linux-arm-kernel@lists•infradead.org>,
<iommu@lists•linux.dev>, <linux-kernel@vger•kernel.org>,
<linux-tegra@vger•kernel.org>
Subject: Re: [PATCH v2 1/2] iommu/arm-smmu-v3: Detect Tegra264 erratum
Date: Fri, 29 May 2026 14:30:22 -0700 [thread overview]
Message-ID: <ahoFbo7KNHiHh+D6@Asurada-Nvidia> (raw)
In-Reply-To: <20260529140830.629738-2-amhetre@nvidia.com>
On Fri, May 29, 2026 at 02:08:29PM +0000, Ashish Mhetre wrote:
> Tegra264 SMMU is affected by 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. The second issue is
> guaranteed to evict the entry. ATC_INV is not affected and must not be
> doubled.
>
> The erratum is not flagged by any SMMUv3 IDR/IIDR register, so it cannot
> be detected from hardware register. Tegra264 boots from device tree only
> and has no ACPI/IORT support, so detection is through device tree only.
>
> Add the ARM_SMMU_OPT_TLBI_TWICE option and set it on instances matching
> the existing "nvidia,tegra264-smmu" compatible. No callers consume the
> option yet, next patch wires the workaround into the CMDQ issue paths.
I was told to avoid "patch": once a patch is applied it becomes
a commit. So, maybe "a subsequent change will wire".
>
> Signed-off-by: Ashish Mhetre <amhetre@nvidia•com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia•com>
next prev parent reply other threads:[~2026-05-29 21:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-29 14:08 [PATCH v2 0/2] iommu/arm-smmu-v3: Tegra264 invalidation workaround Ashish Mhetre
2026-05-29 14:08 ` [PATCH v2 1/2] iommu/arm-smmu-v3: Detect Tegra264 erratum Ashish Mhetre
2026-05-29 21:30 ` Nicolin Chen [this message]
2026-06-01 9:04 ` Ashish Mhetre
2026-05-29 14:08 ` [PATCH v2 2/2] iommu/arm-smmu-v3: Issue CFGI/TLBI twice on Tegra264 Ashish Mhetre
2026-05-29 21:10 ` Nicolin Chen
2026-06-01 9:20 ` Ashish Mhetre
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