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s=default; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Unsubscribe-Post:List-Subscribe:List-Post:List-Owner: List-Archive; bh=j/qonkLTfSJS6fOcfIBVACKrRZK2oHEhnPOu7N9/zz8=; b=rP2S6qUD2i+9 HPp78wilmv51lPsJeYeSL2+Q992YgG8wmyBV8UHhCQaaCj+XNlWTLP49bOIFZlJxpMJQqskrNV1cI PnTqxVJwwABcrId1lVrr/DIfCTfHBeaYZBbzneINJzlpbM++M9QyYMRYTTe77kBfZlZUCGiW6h3T8 pp7jO8yQ2iIZ4KouhqodhcjpbtQqWeWdXPDNUaOspyXHA0WeCD4sVWY5dvra1xuVF3+2KohwcuLWA 1qnlbIlhrbog65pGimvDtWupyLt3sdpY8Q/WySQSASpiHIzybLVSuQHa+8QjB5ZHN0k5V9BHb14eA EW8CJ9wtFqUJa++7UoaqDg==; Received: from 108-223-40-66.lightspeed.sntcca.sbcglobal.net ([108.223.40.66]:44006) by bh-25.webhostbox.net with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.100.1) (envelope-from ) id 1xOe1K-00000002Xpu-1SC1; Wed, 04 Nov 2026 22:09:30 +0530 Message-ID: Date: Wed, 4 Nov 2026 08:39:28 -0800 X-Mailing-List: linux-kernel@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: [RFC PATCH 0/3] watchdog: arm_smc_wdt: allow a list of SMC function ids To: Mateusz Nowicki , Wim Van Sebroeck , linux-watchdog@vger.kernel.org Cc: Julius Werner , Evan Benn , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Maxime Coquelin , Alexandre Torgue , Antonio Borneo , Marek Vasut , devicetree@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20261104161553.30115-1-mateusz.nowicki@posteo.net> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-BWhitelist: no X-Source-IP: 108.223.40.66 X-Source-L: No X-Exim-ID: 1xOe1K-00000002Xpu-1SC1 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 108-223-40-66.lightspeed.sntcca.sbcglobal.net [108.223.40.66]:44006 X-Source-Auth: guenter@roeck-us.net X-Email-Count: 11 X-Org: HG=direseller_whb_net_legacy;ORG=directi; X-Source-Cap: cm9lY2s7YWN0aXZzdG07YmgtMjUud2ViaG9zdGJveC5uZXQ= X-Local-Domain: yes X-CMAE-Envelope: MS4xfJscwhwt6UhdsWyskR8b7SJkyIDz0AgygvfC3Tet5rmv/UEQvAMWoUnBEGnijm7l7UkVqbaUuaAoI3QvFlQUpCziBlIKirG7DRqx/gkBztI2M7Jb1fBr qW9CxEWYX1/m5NsCm6ITHX/C1aMxL5x7kJJnLSbBfY59D5wGcI9nZJuGzQKXr0ifjT7I2D7VIva98O3/AiSEDl3YRc7F2H++Bz2r7XaafL8WGouKG0Y6YaOx On 11/4/26 08:16, Mateusz Nowicki wrote: > Hi all, > > this follows up on Marek's report about the stm32mp2 watchdog [1]. > > A quick recap: the arm,smc-wdt driver talks to the firmware through one > SMC function id that it reads from the device tree, and there is no way > to ask the firmware which id it uses. On the STM32MP2 SoCs that id > changed over time. ST's OP-TEE from ecosystem v5 expects 0xb200005a, > their 4.0.0 fork accepts both, and the 4.8.0 fork as well as upstream > OP-TEE only accept 0xbc000000. > > My earlier patch, commit ae4d08bbe3f4 ("arm64: dts: st: fix arm,smc-id > of the SMC watchdog on stm32mp2"), switched the dtsi to 0xbc000000. That > made the watchdog work with current OP-TEE, but it broke boards that run > the older firmware. So today 6.18.y uses one id and 7.4 the other. When > the kernel and the firmware disagree, nobody pets the watchdog that the > bootloader started, and the board resets after 32 seconds. Marek hit > this even with a recovery kernel, which is about the worst place for it. > So the DT on the board is updated to use the new ID but the firmware itself isn't ? That seems a bit odd; I would have assumed that the DT on a board is kept in sync with its firmware. Is that not the case here ? > The idea from that thread: let arm,smc-id be a list. The driver tries > the ids one by one and keeps the first one the firmware accepts. Older > kernels only read the first cell, so they behave exactly as they do > now. For stm32mp2 the list is <0xbc000000 0xb200005a>. Calling an id > that belongs to some other firmware service would be bad, so the > binding says the list may only hold ids known to be this watchdog. > Would it possibly make sense to check keep a list of known IDs in the driver ? It already checks 0x82003D06, so it might as well check a sequence. Thanks, Guenter > Why RFC: arm,smc-id already exists in firmware/arm,scmi.yaml as a plain > uint32, and dt_binding_check complains when another binding turns it > into an array: > > arm-smc-wdt.yaml: arm,smc-id: multiple incompatible types: uint32-array > arm,scmi.yaml: arm,smc-id: multiple incompatible types: uint32 > > DT folks, is there a way to keep the list in arm,smc-id that you would > be fine with? If not, I can move the extra ids into a new property, > something like: > > arm,smc-id = <0xbc000000>; > arm,smc-alt-ids = <0xb200005a>; > > The driver side would stay the same, it would just read the fallback > ids from the other property. > > One more question: should patches 2 and 3 go to stable as well? Then > 6.18.y would also work with both firmware generations. The 6.18.y > version of patch 3 would turn its 0xb200005a into the same list. > > [1] https://lore.kernel.org/all/1b14e1e4-962f-4391-91fd-b09143641643@nabladev.com/ > > Mateusz Nowicki (3): > dt-bindings: watchdog: arm-smc-wdt: allow a list of SMC ids > watchdog: arm_smc_wdt: try every id of arm,smc-id > arm64: dts: st: list both watchdog SMC ids on stm32mp23 and stm32mp25 > > .../bindings/watchdog/arm-smc-wdt.yaml | 9 +++++++-- > arch/arm64/boot/dts/st/stm32mp231.dtsi | 2 +- > arch/arm64/boot/dts/st/stm32mp251.dtsi | 2 +- > drivers/watchdog/arm_smc_wdt.c | 18 ++++++++++++------ > 4 files changed, 21 insertions(+), 10 deletions(-) > > > base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4