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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b723fa03d3esm238316566b.53.2025.11.04.06.35.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Nov 2025 06:35:07 -0800 (PST) Message-ID: <9ee07db9-508e-4c08-8f79-6ccfd9b646ab@oss.qualcomm.com> Date: Tue, 4 Nov 2025 15:35:05 +0100 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 v3 1/2] dt-bindings: soc: qcom: Add qcom,kaanapali-imem compatible To: Krzysztof Kozlowski , Jingyi Wang Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Robert Marko , Das Srinagesh , aiqun.yu@oss.qualcomm.com, tingwei.zhang@oss.qualcomm.com, trilok.soni@oss.qualcomm.com, yijie.yang@oss.qualcomm.com, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251102-knp-soc-binding-v3-0-11255ec4a535@oss.qualcomm.com> <20251102-knp-soc-binding-v3-1-11255ec4a535@oss.qualcomm.com> <20251104-glaring-rebel-pillbug-a467ca@kuoka> <790ca394-cee2-412b-97d8-c6416b843010@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-ORIG-GUID: MOOSPZWoHDazpQp1oFbHNfpPASCzC22l X-Proofpoint-GUID: MOOSPZWoHDazpQp1oFbHNfpPASCzC22l X-Authority-Analysis: v=2.4 cv=b7O/I9Gx c=1 sm=1 tr=0 ts=690a0f1e cx=c_pps a=HLyN3IcIa5EE8TELMZ618Q==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=6UeiqGixMTsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=L0PDfkbdR_nvDvRPFewA:9 a=QEXdDO2ut3YA:10 a=bTQJ7kPSJx9SKPbeHEYW:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTA0MDEyMSBTYWx0ZWRfX29XL0ZYvriNL p1AWHBNU6lTlSVdVR/nPwl3n2OfTkQ6RkCFK4MyPKJckF4qcwqNz8oNRoxaSJVP174g9PtCrwHN wcF/ctOpzsjIhEJLkThF2DlANuDDPvQnfMypXddIFQoUaGYSfd9rIr+94+xpSUFF+BFJRLHlBqH 5Cx+HZZLdTApHTT7UoC9W6dNIT5AwW0nUVFjXS9A3PeiKKgviDGnZUiTB2vkqX0XXWsrOLCxvBy AA5lxDpCPsoVea9oxUsyrAREOmiHzv5+laxlrVdEFhUT9nWiXuNRsvdzHXBkV+LfTfERMLM6alv qZCIOkesB70XMXa7UooeW8Md9eO5J/oCmtr0DwTjwHc5b+cWEnN29DP4/SP0GyJPUsHzOr+1uPv n4EJyEe9CTMtK5tBj8w9oPDNkHYT1w== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-04_01,2025-11-03_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 phishscore=0 spamscore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2511040121 On 11/4/25 3:26 PM, Krzysztof Kozlowski wrote: > On 04/11/2025 13:32, Konrad Dybcio wrote: >> On 11/4/25 9:16 AM, Krzysztof Kozlowski wrote: >>> On Sun, Nov 02, 2025 at 11:25:06PM -0800, Jingyi Wang wrote: >>>> Document qcom,kaanapali-imem compatible. Kaanapali IMEM is not a syscon or >>>> simple-mfd, also "reboot reason" is not required on Kaanapali like some >>> >>> I do not see correlation. Something is not a syscon, so you add a new >>> generic compatible? No. >>> >>>> other platforms. So define a common "qcom,imem" binding and fallback to it. >>> >>> You did not define fallback to it! >>> >>> ... >>> >>>> + - items: >>>> + - enum: >>>> + - qcom,kaanapali-imem >>>> + - const: qcom,imem >>> >>> I do not understand what this generic compatible is supposed to express, >>> not explained in commit msg. Considering this wasn't before, it is a >>> major and really undesired change. It also makes no sesne. There was no >>> generic compatible before but "if not syscon" now this must have generic >>> compatible, what? >> >> So IMEM (or SYSTEM_IMEM more specifically as opposed to BOOT_IMEM which >> you can take your guesses what it's used for) is to the best of our >> understanding just a piece of SRAM that's accessible by multiple >> processors/subsystems on the SoC. >> >> A smaller region within it ("shared IMEM") is a little bit of a dumping >> ground for various (incl. runtime) configuration and debug magic data >> and that's usually what Linux is concerned with. >> >> IMEM is currently described as a simple-mfd+syscon, which it is clearly >> not. The former, as we've established in the past, was used as a hack to >> have something call of_platform_populate(). >> >> I think that in turn is only necessary for the old arm32 DTs which have >> a syscon-reboot-mode node under IMEM (and I think that's where the syscon >> compatible comes from). >> >> Should we make the switch to mmio-sram and settle this discussion? >> It would probably require convincing the sram maintainer to add that >> of_platform_populate() call in its probe func and making syscon-reboot >> not depend on a syscon (not like it's very hard) > > This I got, but nothing here explains why you need generic compatible. > To re-iterate: there was no generic compatible before, now there is. > Writing bindings and numerous reviews from DT maintainers ask not to use > generic compatibles. OK so let's not worry about a generic compatible. IMEM exists since MSM8974 and it only had major hw updates with SM8550. They don't impact the software interface though, so qcom,msm8974-imem is OK. There's a separate control/status register address space for each instance of this IP (usually far apart from the actual SRAM pool), which Linux doesn't have to care about. Konrad