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[91.159.24.186]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-39c6f682129sm7596531fa.1.2026.07.08.05.01.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jul 2026 05:01:31 -0700 (PDT) Message-ID: <74608907-dc8a-42c5-b188-0bdb08d6be77@linaro.org> Date: Wed, 8 Jul 2026 15:01:30 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/5] media: qcom: jpeg: Add Qualcomm JPEG V4L2 encoder To: Dmitry Baryshkov Cc: "Gjorgji Rosikopulos (Consultant)" , Atanas Filipov , linux-media@vger.kernel.org, bryan.odonoghue@linaro.org, loic.poulain@oss.qualcomm.com, mchehab@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, andersson@kernel.org, konradybcio@kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org References: <20260706071113.383215-1-atanas.filipov@oss.qualcomm.com> <20260706071113.383215-6-atanas.filipov@oss.qualcomm.com> <51a0abf2-2a72-4551-894b-2c2de91ba0c2@linaro.org> <74a5b549-987c-4dac-a1a0-ff81150cd6ab@oss.qualcomm.com> <56f1fd7e-42bc-4034-81dc-302cb7c22951@linaro.org> From: Vladimir Zapolskiy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 7/8/26 14:35, Dmitry Baryshkov wrote: > On Wed, Jul 08, 2026 at 01:28:46PM +0300, Vladimir Zapolskiy wrote: >> Hi Gjorgji. >> >> On 7/8/26 12:32, Gjorgji Rosikopulos (Consultant) wrote: >>> Hi Vlad, >>> >>> On 7/8/2026 11:47 AM, Vladimir Zapolskiy wrote: >>>> Hi Gjorgji. >>>> >>>> On 7/7/26 16:24, Gjorgji Rosikopulos (Consultant) wrote: >>>>> Hi Vlad, >>>>> >>>>> On 7/6/2026 10:46 AM, Vladimir Zapolskiy wrote: >>>>> >>>>>>> >>>>>>> +            interconnects = <&gem_noc MASTER_AMPSS_M0 >>>>>>> QCOM_ICC_TAG_ACTIVE_ONLY >>>>>>> +                             &config_noc SLAVE_CAMERA_CFG >>>>>>> QCOM_ICC_TAG_ACTIVE_ONLY>, >>>>>>> +                            <&mmss_noc MASTER_CAMNOC_HF >>>>>>> QCOM_ICC_TAG_ALWAYS >>>>>>> +                             &mc_virt SLAVE_EBI_CH0 >>>>>>> QCOM_ICC_TAG_ALWAYS>, >>>>>>> +                            <&mmss_noc MASTER_CAMNOC_SF >>>>>>> QCOM_ICC_TAG_ALWAYS >>>>>>> +                             &mc_virt SLAVE_EBI_CH0 >>>>>>> QCOM_ICC_TAG_ALWAYS>; >>>>>>> +            interconnect-names = "cpu-cfg", >>>>>>> +                                 "hf-mnoc", >>>>>>> +                                 "sf-mnoc"; >>>>>> >>>>>> This is the topic, which may raise a disagreement, but I'll repeat my >>>>>> position about the need to remove all "CAMSS bus" specific resources from >>>>>> the device node, they are found and should be allocated on parent's side. >>>>> >>>>> The interconnect has functionality to handle bw requests from different >>>>> clients. >>>>> >>>>> Yes the best will be to have camss interconnect, so jpeg and other hw's >>>>> to vote >>>>> >>>>> on that (actually it is possible in icc framework) but what is the >>>>> benefit of moving >>>>> >>>>> those to camss? Is it not better to create camss icc. I understand >>>>> you want them to be on parent side. But how to vote on bw? Most of the >>>>> time it >>>> >>>> Let's concentrate on hardware bindings description, no APIs, votes etc. >>>> at this point of discussion. >>> I agree but there should be an API for icc voting which Jpeg need to use, >>> currently it is fixed to some values, but voting need to become dynamic >>> at some point of time, because it depends on runtime parameters, resolution >>> format etc.> >> >> Sure, but I believe it's quite clear that any software implementation >> should be discussed only when the hardware description is fixed. >> >>>> There is SM8250 CAMSS device, which serves as a hierarchical parent (or >>>> could be considered as a "bus" device) to this new JPEG encoder device >>>> and probably to a number of future IPs under CAMSS. All CAMSS sub-devices >>>> get hardware descriptions as children device tree nodes of CAMSS parent >>>> device tree node naturally. >>> I agree the device tree is best to represent real hw topology. > >> >> Well, it's not just the best, it's the only possible way. >> >>>> Copying of the same identical information about clocks, interconnects >>>> and power domains from the hierarchical parent device to children devices >>>> is not needed, and practically it only lowers signal-to-noise ratio. >>> Here also i tend to agree.> >>>> Since information about the actual defect in hardware description is >>>> reported, the problem can and should be avoided, the handling of a better >>>> hardware description and dealing with any kind of complexity will be done >>>> in the CAMSS and/or CAMSS children drivers. >>>> >>>> If you need to get a bit more formal point of view on the matter, I'd >>>> prefer to see descriptions of hardware properties organised in a tree >>>> topology rather than in the originally proposed star topology. By doing >>>> it the system complexity is reduced from N to 1. >>> >>> Maybe I'm missing the whole picture of your proposal, but I want to add my >>> point of view on this matter. >>> >>> The JPEG encoder HW block has no dependency on the other processing HW >>> blocks in the camera subsystem >>> >>> It shares resources like camnoc, clocks, GDSC, etc., >>> but does not share anything with the other HW processing blocks. For me, >>> the JPEG driver should not have SW architectural dependencies on CAMSS. >> >> To move forward there should be a clear answer to a simple question, >> does Qualcomm JPEG encoder IP belong to CAMSS group of devices or not? >> >> If no, then JPEG encoder device tree node shall be located outside of >> CAMSS device tree node, all resources needed for JPEG encoder device >> operation get their descrition in this stand-alone device tree node. >> >> If yes, then JPEG encoder device tree node is a child of CAMSS "bus" >> device tree node, and only resources specific to JPEG encoder device >> are described in its device tree node, because other resources are >> already described in the parent device tree node. > > 2c from my side (for both sides of the discussion). Please keep it > separate, if the block simply uses the resource which is also used by > the parent (e.g. there are no special requirements on the AHB or sleep > clocks) or if the device needs to actuall cast a vote on a particular > resource (e.g. for this to function at this performance level, the MMCX > needs to be at the turbo level OR for this to function at this > performance level it will use 123 MHz of the AXI clock). In the latter > case the resources must be described as a part of the device. > Even this "description as a part of the device" might be not quite necessary in whole, let me try to explain. No doubts resource usage policies specific to a child device should be naturally described in child device tree node, and it's applicable to any kind of hardware policies (like opp tables etc.), but a list of needed hardware resources still can be obtained (also by a driver) from the parent, whenever it is found applicable and unambiguous. This is to separate planes of hardware dependencies and policies/controls needed for hardware usage. -- Best wishes, Vladimir