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[159.2.239.150]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-532a1a27288sm12168121cf.28.2026.09.18.05.11.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 05:11:33 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1x7XRE-00000001A2N-2VCC; Fri, 18 Sep 2026 09:11:32 -0300 Date: Fri, 18 Sep 2026 09:11:32 -0300 From: Jason Gunthorpe To: Peng Fan Cc: Krzysztof Kozlowski , Will Deacon , Robin Murphy , Frank Li , "Joerg Roedel (AMD)" , Jean-Philippe Brucker , linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Peng Fan Subject: Re: [PATCH RFC 0/4] iommu/arm-smmu-v3: Support shared Stream IDs Message-ID: <20260918121132.GA11599@ziepe.ca> References: <20260916-smmu-shared-sid-v1-0-517384504aee@nxp.com> <20260916161018.GE3196566@ziepe.ca> <20260917144804.GI3196566@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260918_051137_808925_6D176CB3 X-CRM114-Status: GOOD ( 12.80 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 18, 2026 at 07:48:34PM +0800, Peng Fan wrote: > However, the DMA channel case was just one example - the shared-SID > need exists independently of it. Our SoC (i.MX95) has only 64 SIDs > total, serving MMC, SD, NET, PCI, DMA, NPU, DSP, DISPLAY and more. > Some of these are genuinely separate platform devices (distinct DT > nodes, distinct drivers) that share a SID by hardware design because > the SID space is exhausted. > > That cross-IP case cannot be solved by DT restructuring - the devices > really are separate. Would you be open to reviewing the shared-SID > SMMU support (patches 1-4) on that basis, independent of the DMA > channel question? I think you should revise your commit message/cover letter to focus on something that is not a DT abuse and try again IIRC Robin said the SID aliasing was a PITA on SMMUv2 so it really needs to have a strong reason. Jason