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([2001:b07:2ec:601d:4b26:1672:75c7:805a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a2104627e0sm14106125e9.9.2026.10.22.11.05.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Oct 2026 11:05:40 -0700 (PDT) Message-ID: <31970f28-5415-4e78-aa0f-51f15d779e1b@gmail.com> Date: Thu, 22 Oct 2026 20:05:38 +0200 X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 03/13] drm/msm: look for lpac from dts From: Anna Maniscalco To: Dmitry Baryshkov , Akhil P Oommen Cc: Rob Clark , Will Deacon , Robin Murphy , Joerg Roedel , Sean Paul , Konrad Dybcio , Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Marijn Suijten , David Airlie , Simona Vetter , Bjorn Andersson , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , iommu@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, devicetree@vger.kernel.org References: <20260705-descriptive-name-lpac-upstream-v1-0-01d50c3e0c99@gmail.com> <20260705-descriptive-name-lpac-upstream-v1-3-01d50c3e0c99@gmail.com> <54cb37bb-aaa5-4c5d-a563-acca4822dd35@oss.qualcomm.com> <1f6db59c-b7a9-41a1-8022-6713365fa09e@gmail.com> Content-Language: en-US In-Reply-To: <1f6db59c-b7a9-41a1-8022-6713365fa09e@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/22/26 2:54 PM, Anna Maniscalco wrote: > On 7/9/26 9:39 PM, Dmitry Baryshkov wrote: >> On Thu, Jul 09, 2026 at 05:54:23PM +0300, Dmitry Baryshkov wrote: >>> On Thu, Jul 09, 2026 at 07:12:39PM +0530, Akhil P Oommen wrote: >>>> On 7/7/2026 10:09 PM, Dmitry Baryshkov wrote: >>>>> On Tue, Jul 07, 2026 at 05:02:43PM +0200, Anna Maniscalco wrote: >>>>>> On 7/6/26 5:04 PM, Dmitry Baryshkov wrote: >>>>>>> On Sun, Jul 05, 2026 at 09:13:37PM +0200, Anna Maniscalco wrote: >>>>>>>> In order to associate the SID used by LPAC to it's own domain and >>>>>>>> context bank we need a separate node on the DTS. >>>>>>> Can we use iommu-map instead of adding a new device using the same >>>>>>> addresses? You provide zero explanations, but it seems like you are >>>>>>> trying to separate a part of the GPU into a separate device, but >>>>>>> it's >>>>>>> unnecessary. >>>>>> What I was trying to say is that we need to map sid0 and sid1 to >>>>>> different >>>>>> context banks. >>>>>> >>>>>>  From what I recall, so long as we use the same dt node, the >>>>>> iommu drivert >>>>>> provides no way of doing this. >>>>>> >>>>>> What kgsl does is having a node for the iommu and then subnodes >>>>>> for gfx lpac >>>>>> and secure. >>>>>> >>>>>> The address on the lpac device doesn't really matter. I have very >>>>>> limted >>>>>> knowledge of DTSs but I think we could just leave it out altogether? >>>>> I think, you were poined to the Glymur Iris patches. Another >>>>> option is >>>>> the QDA driver being submitted too. Both ot them use iommu-map to >>>>> describe the same usecase - a set of SIDs which are used by the >>>>> device >>>>> but which should not be a part of the defaut set. With it in place >>>>> you >>>>> don't need to have separate qcom,lpac devices, no additional >>>>> properties, >>>>> etc. >>>>> >>>>> I'd recommend following the same approach. >>>> iiuc, the conclusion in this recent thread is to use child nodes for a >>>> similar case: >>>> https://lore.kernel.org/all/20260618151745.GD231643@ziepe.ca/ >>> Let me check internally. >> After a brief discussion: it can be either, depending on what suites >> better (and if you can persuade DMA / IOMMU maintainers to let one extra >> bus or not). >> > One thing sashiko is pointing out is that new dt should work with hold > kernel so, in general moving sid1 from there would break it since old > kernels don't know how to handle them separately. > > Not sure how to address this. > > Best regards, Also, looking into iommu-map, it seems like I would ultimately still need to add a child device. Best regards, -- Anna Maniscalco