From: mateusz.nowicki@posteo.net
To: Marek Vasut <marex@nabladev.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
Alexandre Torgue <alexandre.torgue@foss.st.com>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
Thomas BOURGOIN <thomas.bourgoin@st.com>,
Rob Herring <robh@kernel.org>,
krzk+dt@kernel.org, Conor Dooley <conor+dt@kernel.org>,
Lionel DEBIEVE <lionel.debieve@foss.st.com>,
Amelie DELAUNAY <amelie.delaunay@foss.st.com>,
Patrice Chotard <patrice.chotard@foss.st.com>,
devicetree@vger.kernel.org,
linux-stm32@st-md-mailman.stormreply.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kernel <kernel@dh-electronics.com>,
Geert Uytterhoeven <geert+renesas@glider.be>,
"laurent.pinchart" <laurent.pinchart@ideasonboard.com>,
Fabrice GASNIER <fabrice.gasnier@foss.st.com>,
Stefano Babic <sbabic@nabladev.com>,
Etienne Carriere <etienne.carriere@foss.st.com>
Subject: Re: [PATCH] arm64: dts: st: fix arm,smc-id of the SMC watchdog on stm32mp2
Date: Sat, 31 Oct 2026 20:59:19 +0000 [thread overview]
Message-ID: <799394b5ac7067cd2bb2e06117e53ec3@posteo.net> (raw)
In-Reply-To: <7ff5f937-144b-41fc-ab0d-82271a01dde1@nabladev.com>
Hi Marek,
> But maybe there is some way to probe for the correct ARM SMC WDT ID ?
I agree, the ID is not discoverable. A revert or a board override
would not help firmware built with a custom CFG_WDT_SM_HANDLER_ID
either. Sorry for the trouble on your board.
I like the fallback idea. My suggestion:
- arm,smc-id becomes a list of IDs.
- The driver tries them in order until SMCWD_INIT succeeds.
- The SoC dtsi lists <0xbc000000 0xb200005a>.
- Boards with a custom ID override the list.
- Older kernels read only the first cell, so nothing breaks there.
Trying a wrong ID is harmless. Old and new firmware both just return
an error for an ID they do not know, as your two cases and my DK show.
One catch: OP-TEE answers an unknown call with 0xFFFFFFFF in w0, and
smcwd_call() compares a0 with PSCI_RET_NOT_SUPPORTED as a 64-bit
value. The driver gets -EIO, not -ENODEV, so the fallback should move
to the next ID on any error.
If you and the watchdog maintainers are fine with this, I can send
the binding and driver patches.
Best regards,
Mateusz
next prev parent reply other threads:[~2026-10-31 20:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-07 9:14 [PATCH] arm64: dts: st: fix arm,smc-id of the SMC watchdog on stm32mp2 Mateusz Nowicki
2026-09-08 8:52 ` [Linux-stm32] [PATCH] arm64: dts: st: fix arm, smc-id " Antonio Borneo
2026-09-23 11:52 ` [PATCH] arm64: dts: st: fix arm,smc-id " Mateusz Nowicki
2026-09-28 8:45 ` Alexandre TORGUE
2026-10-31 5:59 ` Marek Vasut
2026-10-31 8:45 ` Arnd Bergmann
2026-10-31 12:00 ` mateusz.nowicki
2026-10-31 13:35 ` Marek Vasut
2026-10-31 20:59 ` mateusz.nowicki [this message]
2026-11-01 4:47 ` Marek Vasut
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