linux-kernel - Re: [PATCH 01/13] dt-bindings: i2c: nomadik: add timeout-usecs property bindings

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Message-Id: <CZ94LGRSF9KN.15ZO1VRMIQVR8@bootlin.com>
Date: Mon, 19 Feb 2024 15:29:57 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Linus Walleij" <linus.walleij@...aro.org>
Cc: "Rob Herring" <robh@...nel.org>, "Andi Shyti" <andi.shyti@...nel.org>,
 "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley"
 <conor+dt@...nel.org>, "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
 <linux-arm-kernel@...ts.infradead.org>, <linux-i2c@...r.kernel.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linux-mips@...r.kernel.org>, "Gregory Clement"
 <gregory.clement@...tlin.com>, "Vladimir Kondratiev"
 <vladimir.kondratiev@...ileye.com>, "Thomas Petazzoni"
 <thomas.petazzoni@...tlin.com>, "Tawfik Bayouk"
 <tawfik.bayouk@...ileye.com>
Subject: Re: [PATCH 01/13] dt-bindings: i2c: nomadik: add timeout-usecs
 property bindings

Hello,

On Mon Feb 19, 2024 at 3:06 PM CET, Linus Walleij wrote:
> Hi Théo,
>
> thanks for your patch!
>
> On Fri, Feb 16, 2024 at 10:16 AM Théo Lebrun <theo.lebrun@...tlin.com> wrote:
>
> > i2c-mpc (fsl,timeout) and i2c-gpio (i2c-gpio,timeout-ms). I agree this
> > prop has no reason to be compatible-specific.
> >
> > Feedback from dt-bindings and I2C host maintainers would be useful: what
> > should the property be named? Having the unit makes it self-descriptive,
> > which sounds like a good idea to me. timeout-usecs, timeout-us, another
> > option?
>
> Use i2c-transfer-timeout-ms in my opinion, so it us crystal clear
> what that property is for.

Using µs (microseconds) would be OK? I'm not sure yet about the exact
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 µs timeout:
i2c-scl-clk-low-timeout-us

Thanks,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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