linux-kernel - Re: [PATCH 02/13] dt-bindings: i2c: nomadik: add mobileye,eyeq5-i2c bindings and example

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Message-Id: <CZ6FUECKEX2B.36QWZZA5EYPI@bootlin.com>
Date: Fri, 16 Feb 2024 11:40:50 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Krzysztof Kozlowski" <krzysztof.kozlowski@...aro.org>, "Rob Herring"
 <robh@...nel.org>
Cc: "Linus Walleij" <linus.walleij@...aro.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 02/13] dt-bindings: i2c: nomadik: add mobileye,eyeq5-i2c
 bindings and example

Hello,

On Fri Feb 16, 2024 at 11:33 AM CET, Krzysztof Kozlowski wrote:
> On 16/02/2024 11:18, Théo Lebrun wrote:
> > 
> >>> +        mobileye,id:
> >>> +          $ref: /schemas/types.yaml#/definitions/uint32
> >>> +          description: Platform-wide controller ID (integer starting from zero).
> >>
> >> instance indexes are a NAK. You can use i2cN aliases if you must.
> >>
> >> Why do you need it? To access OLB? If so, add cell args to the OLB 
> >> phandle instead.
> > 
> > Why we do what we do: I2C controller must write a 2 bit value depending
> > on the bus speed. All I2C controllers write into the same register.
>
> Which register?  Your devices do not share IO address space.

mobileye,olb is a prop with a phandle to a syscon. That syscon contains
the register we are interested in.

The Linux code side of things is in the following patch. We use
syscon_regmap_lookup_by_phandle().

   [PATCH 10/13] i2c: nomadik: support Mobileye EyeQ5 I2C controller
   https://lore.kernel.org/lkml/20240215-mbly-i2c-v1-10-19a336e91dca@bootlin.com/

Thanks,

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