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Sat, 18 Jul 2026 07:32:33 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wl65h-00000006T6V-0EUE; Sat, 18 Jul 2026 11:32:33 -0300 Date: Sat, 18 Jul 2026 11:32:33 -0300 From: Jason Gunthorpe To: Daniel Drake Cc: "Joerg Roedel (AMD)" , Will Deacon , Robin Murphy , 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 5/6] iommu: Add Broadcom BCM2712 IOMMU driver Message-ID: <20260718143233.GE701389@ziepe.ca> References: <20260712-bcm2712-iommu-submit-v1-0-80e10cdde2ea@reactivated.net> <20260712-bcm2712-iommu-submit-v1-5-80e10cdde2ea@reactivated.net> <20260712221125.GD1835788@ziepe.ca> <57f5675c-8bcd-4022-978b-9f7933bb0032@reactivated.net> Precedence: bulk X-Mailing-List: devicetree@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: <57f5675c-8bcd-4022-978b-9f7933bb0032@reactivated.net> On Sat, Jul 18, 2026 at 09:39:48AM +0100, Daniel Drake wrote: > I don't think I can use that because this setup uses an IOVA aperture at > base 0xA00000000, whereas generic_pt assumes it is managing a 0-indexed > virtual address space. So the driver has to intercept every incoming IOVA > and translate for the aperture, see how map_pages calls: When you say aperture here you mean we place an IOPTE at VA 0 but the dma_addr_t for that has to be adjusted to 0xA00000000 ? I wonder if DT can do this with dma-ranges or something, we have many other conditions where the dma_addr_t and the internal physical have offsets.. > I was wondering about making iommupt understand apertures and > translate accordingly, but I imagine you would want to keep that > kind of thing out of the generic fast path? We already have pt_full_va_prefix() which isn't strictly an offset but it it probably matches what this HW does. You can implement it in the broadcom format and return the prefix value. So long as the vasz fits within those trailing 0s. That's basically free and has no runtime cost on other formats. Jason