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Sun, 16 Aug 2026 09:57:30 -0700 (PDT) Received: from ziepe.ca ([142.166.156.215]) by smtp.gmail.com with ESMTPSA id af79cd13be357-936ce0898efsm784134485a.12.2026.08.16.09.57.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 16 Aug 2026 09:57:29 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wveAq-00000005W02-2MZ2; Sun, 16 Aug 2026 13:57:28 -0300 Date: Sun, 16 Aug 2026 13:57:28 -0300 From: Jason Gunthorpe To: Daniel Drake Cc: Robin Murphy , "Joerg Roedel (AMD)" , Will Deacon , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Florian Fainelli , Broadcom internal kernel review list , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, nick.hollinghurst@raspberrypi.com Subject: Re: [PATCH v2 4/5] iommu: Add Broadcom BCM2712 IOMMU driver Message-ID: <20260816165728.GB933791@ziepe.ca> References: <20260727-bcm2712-iommu-submit-v2-0-0247b5c03de8@reactivated.net> <20260727-bcm2712-iommu-submit-v2-4-0247b5c03de8@reactivated.net> <3e7ba95b-51e7-48e4-aea5-f86db1739ac2@arm.com> 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-20260816_095731_983896_608E1060 X-CRM114-Status: GOOD ( 12.88 ) 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 Sun, Aug 16, 2026 at 01:50:32PM +0100, Daniel Drake wrote: > Let me know if anything sounds off! It sounds reasonable to me, and at least from this starting point you could imaging trying to build a scheme where individual devices in the group can use the group wide paging or identity translation. I'm not sure how that could look, but at least from a DT and driver perspective it is not such a big leap. There are several unrelated topics going on where it does seem we are not giving enough control to the end driver about how translations work when the core happens to bundle streams all together into one group or even one device. So maybe there is some merit in coming up with a way to have multiple translations active within a group to greater expose what the HW can actually do. Jason