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Mon, 17 Aug 2026 06:44:17 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wvxdQ-00000005wLX-438N; Mon, 17 Aug 2026 10:44:16 -0300 Date: Mon, 17 Aug 2026 10:44:16 -0300 From: Jason Gunthorpe To: Ekansh Gupta Cc: Oded Gabbay , Jonathan Corbet , Shuah Khan , Randy Dunlap , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , "Joerg Roedel (AMD)" , Will Deacon , Robin Murphy , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Sumit Semwal , Christian =?utf-8?B?S8O2bmln?= , Bharath Kumar , Chenna Kesava Raju , srinivas.kandagatla@oss.qualcomm.com, dmitry.baryshkov@oss.qualcomm.com, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-arm-msm@vger.kernel.org, llvm@lists.linux.dev, iommu@lists.linux.dev, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org Subject: Re: [PATCH v2 05/15] iommu: Add QDA compute context bank bus to iommu_buses Message-ID: <20260817134416.GA1415075@ziepe.ca> References: <20260817-qda-v2-v2-0-69a02e9090d4@oss.qualcomm.com> <20260817-qda-v2-v2-5-69a02e9090d4@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260817-qda-v2-v2-5-69a02e9090d4@oss.qualcomm.com> On Mon, Aug 17, 2026 at 10:17:40AM +0530, Ekansh Gupta wrote: > Register the QDA compute context bank bus (qda-compute-cb) with the > IOMMU subsystem by adding it to the iommu_buses[] array. > > The QDA driver creates synthetic devices on this bus to represent > IOMMU context banks (CBs). Each CB device needs its own IOMMU domain > so that the DSP memory manager can enforce per-session address space > isolation. Without this registration, the IOMMU subsystem does not > probe CB devices for IOMMU groups and of_dma_configure() in the bus > dma_configure callback has no IOMMU domain to attach to. I didn't notice a clear explanation of the proposed DT schema for this But it looks awfully similar to the other driver that was creating a kernel synthetic bus for actual real HW, that wasn't well liked. What is this for? Why can't you have a normal DT binding for the iommu with normal devices? Jason