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([2a01:e0a:982:cbb0:f7cc:460c:56ae:45a]) by smtp.gmail.com with ESMTPSA id c12-20020adffb4c000000b0022a3a887ceasm3612872wrs.49.2022.11.18.05.30.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Nov 2022 05:30:24 -0800 (PST) Message-ID: Date: Fri, 18 Nov 2022 14:30:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.3 From: neil.armstrong@linaro.org Reply-To: neil.armstrong@linaro.org Subject: Re: [PATCH 1/2] dt-bindings: reserved-memory: document Qualcomm MPSS DSM memory Content-Language: en-US To: Krzysztof Kozlowski , Bjorn Andersson , Konrad Dybcio , Krzysztof Kozlowski , Rob Herring , Andy Gross , Frank Rowand Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org References: <20221114-narmstrong-sm8550-upstream-mpss_dsm-v1-0-158dc2bb6e96@linaro.org> <20221114-narmstrong-sm8550-upstream-mpss_dsm-v1-1-158dc2bb6e96@linaro.org> <38fff21b-3e75-13f9-664e-a115bc527b67@linaro.org> <9aa23650-6ae1-3844-7cf3-6812dc023c11@linaro.org> Organization: Linaro Developer Services In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 18/11/2022 11:45, Krzysztof Kozlowski wrote: > On 17/11/2022 10:47, Neil Armstrong wrote: >>> >>>> + >>>> +properties: >>>> + compatible: >>>> + const: qcom,mpss-dsm-mem >>> >>> Why do we need dedicated binding and compatible for it instead of using >>> memory-region phandle in the device? >> >> So like rmtfs, this memory zone is shared between APPS and the MPSS subsystem. >> >> Like rmtfs it makes no sense to link it to the MPSS PAS, since it's only a launcher, >> it doesn't represent the MPSS subsystem. > > This also does not represent a device. Memory region is not a device, so > this is as well not correct representation of hardware. I never used the term device so far, but a shared memory region with a platform specific process to share the region between subsystems. > >> >> In the PAS startup process, the resources are released from APPS once the MPSS subsystem >> is running, which is not the case with the MPSS DSM where it must be shared during the whole >> lifetime of the system. > > I don't think that PAS releases the region. I checked the > qcom_q6v5_pas.c and there is only ioremap. The device stays loaded thus > the memory stays mapped. Yes PAS does release the firmware region when the firmware is started, qcom_scm_pas_metadata_release() does that. > > We have already three of such "memory region devices" and we keep > growing it. It's not scalable. If we want to properly describe this, we must then represent the MPSS subsystem and associate this memory region. > > Best regards, > Krzysztof Thanks, Neil >