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Sun, 26 Jul 2026 09:23:21 -0700 (PDT) Received: from jgg by jggl with local (Exim 4.95) (envelope-from ) id 1wo1dJ-0001U5-2C; Sun, 26 Jul 2026 13:23:21 -0300 Date: Sun, 26 Jul 2026 13:23:21 -0300 From: Jason Gunthorpe To: Ashish Mhetre Cc: catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, skhan@linuxfoundation.org, robin.murphy@arm.com, joro@8bytes.org, nicolinc@nvidia.com, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-tegra@vger.kernel.org Subject: Re: [PATCH v9 4/4] iommu/arm-smmu-v3: Enable CFGI/TLBI-repeat workaround on Tegra264 Message-ID: References: <20260726081904.1408859-1-amhetre@nvidia.com> <20260726081904.1408859-5-amhetre@nvidia.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260726081904.1408859-5-amhetre@nvidia.com> On Sun, Jul 26, 2026 at 08:19:04AM +0000, Ashish Mhetre wrote: > 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. > > Signed-off-by: Ashish Mhetre > --- > 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(-) Reviewed-by: Jason Gunthorpe Jason