From: Ashish Mhetre <amhetre@nvidia•com>
To: Nicolin Chen <nicolinc@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: Mon, 1 Jun 2026 14:34:37 +0530 [thread overview]
Message-ID: <ee6321cd-44f5-4ce7-aa32-27e1fb886238@nvidia.com> (raw)
In-Reply-To: <ahoFbo7KNHiHh+D6@Asurada-Nvidia>
On 5/30/2026 3:00 AM, Nicolin Chen wrote:
> 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".
Sure, I'll update it in next version.
>> Signed-off-by: Ashish Mhetre <amhetre@nvidia•com>
> Reviewed-by: Nicolin Chen <nicolinc@nvidia•com>
Thanks Nicolin.
next prev parent reply other threads:[~2026-06-01 9:05 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
2026-06-01 9:04 ` Ashish Mhetre [this message]
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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