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Date: Wed, 21 Feb 2024 17:58:13 +0100
Message-Id: <CZAX02IL1N1J.2GQR9D73GLRZB@bootlin.com>
From: =?utf-8?q?Th=C3=A9o_Lebrun?= <theo.lebrun@bootlin.com>
Subject: Re: [PATCH 01/13] dt-bindings: i2c: nomadik: add timeout-usecs
 property bindings
Cc: "Rob Herring" <robh@kernel.org>, "Andi Shyti" <andi.shyti@kernel.org>,
 "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>, "Conor Dooley"
 <conor+dt@kernel.org>, "Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
 <linux-arm-kernel@lists.infradead.org>, <linux-i2c@vger.kernel.org>,
 <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
 <linux-mips@vger.kernel.org>, "Gregory Clement"
 <gregory.clement@bootlin.com>, "Vladimir Kondratiev"
 <vladimir.kondratiev@mobileye.com>, "Thomas Petazzoni"
 <thomas.petazzoni@bootlin.com>, "Tawfik Bayouk"
 <tawfik.bayouk@mobileye.com>
To: =?utf-8?q?Th=C3=A9o_Lebrun?= <theo.lebrun@bootlin.com>, "Linus Walleij"
 <linus.walleij@linaro.org>
References: <20240215-mbly-i2c-v1-0-19a336e91dca@bootlin.com>
 <20240215-mbly-i2c-v1-1-19a336e91dca@bootlin.com>
 <20240216022704.GB850600-robh@kernel.org>
 <CZ6E24VPJKJG.35LACFD6ZV5KE@bootlin.com>
 <CACRpkdZZhhzg5SY7U5dv_OfLEVejRFom4V9nCfkQXunAw1ZXSw@mail.gmail.com>
 <CZ94LGRSF9KN.15ZO1VRMIQVR8@bootlin.com>
In-Reply-To: <CZ94LGRSF9KN.15ZO1VRMIQVR8@bootlin.com>

Hello,

On Mon Feb 19, 2024 at 3:29 PM CET, Th=C3=A9o Lebrun wrote:
> On Mon Feb 19, 2024 at 3:06 PM CET, Linus Walleij wrote:
> > On Fri, Feb 16, 2024 at 10:16=E2=80=AFAM Th=C3=A9o Lebrun <theo.lebrun@=
bootlin.com> wrote:
> > > i2c-mpc (fsl,timeout) and i2c-gpio (i2c-gpio,timeout-ms). I agree thi=
s
> > > prop has no reason to be compatible-specific.
> > >
> > > Feedback from dt-bindings and I2C host maintainers would be useful: w=
hat
> > > should the property be named? Having the unit makes it self-descripti=
ve,
> > > which sounds like a good idea to me. timeout-usecs, timeout-us, anoth=
er
> > > option?
> >
> > Use i2c-transfer-timeout-ms in my opinion, so it us crystal clear
> > what that property is for.
>
> Using =C2=B5s (microseconds) would be OK? I'm not sure yet about the exac=
t
> timeout desired but a one millisecond granularity might not be enough
> for the Mobileye usecase.
>
> Expect incoming patches to use the I2C controller in Fast Mode Plus
> (1Mbps) and High Speed Mode (3.4Mbps). Gotta go fast!
>
> > As Rob mentioned this isn't in the kernel schemas but in dtschema, so
> > you need to patch this:
> > https://github.com/robherring/dt-schema
>
> Indeed. The other question if we do microseconds is the
> suffix: -us, -usecs, -microseconds, etc? I picked -usecs for my v1, but
> a grep tells me I am the only user of this suffix. -us is much more
> common.
>
> BTW i2c-controller.yaml already has a =C2=B5s timeout:
> i2c-scl-clk-low-timeout-us

Note: I've sent a draft patch to dt-schema. See:
https://github.com/devicetree-org/dt-schema/pull/129

Feedback from I2C maintainers would confirm or infirm that this goes in
the right direction.

Thanks,

--
Th=C3=A9o Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com