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[159.2.239.150]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93b81d19df1sm251902985a.45.2026.09.16.09.10.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Sep 2026 09:10:19 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1x6sDC-00000009bqL-1M2P; Wed, 16 Sep 2026 13:10:18 -0300 Date: Wed, 16 Sep 2026 13:10:18 -0300 From: Jason Gunthorpe To: "Peng Fan (OSS)" Cc: Will Deacon , Robin Murphy , "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: <20260916161018.GE3196566@ziepe.ca> References: <20260916-smmu-shared-sid-v1-0-517384504aee@nxp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260916-smmu-shared-sid-v1-0-517384504aee@nxp.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260916_091022_047240_8D6EE2B1 X-CRM114-Status: UNSURE ( 9.84 ) X-CRM114-Notice: Please train this message. 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 Wed, Sep 16, 2026 at 11:12:33PM +0800, Peng Fan (OSS) wrote: > Some SoCs have a limited number of IOMMU Stream IDs (SIDs) and > hardware that inherently shares them. For example, the NXP i.MX95 > eDMA controller has 64 channels where each TX/RX pair is assigned > a single SID by the hardware - the two channel devices are distinct > from Linux's perspective but present the same SID to the SMMU. Is that a reflection of poor DT modelling though? Why must a TX/RX *PAIR* have two platform_devices nodes? Fix it there and you don't need any of this? Or is there more? Jason