linux-kernel - Re: [PATCH 1/3] dt-bindings: i2c: gpio: Add 'transition-delay-ms' property

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Date: Mon, 27 May 2024 16:38:19 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Bastien Curutchet <bastien.curutchet@...tlin.com>,
 Peter Rosin <peda@...ntia.se>, Andi Shyti <andi.shyti@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Peter Korsgaard <peter.korsgaard@...co.com>, Wolfram Sang <wsa@...nel.org>
Cc: linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, herve.codina@...tlin.com,
 christophercordahi@...ometrics.ca
Subject: Re: [PATCH 1/3] dt-bindings: i2c: gpio: Add 'transition-delay-ms'
 property

On 27/05/2024 13:39, Bastien Curutchet wrote:
> The i2c-gpio-mux can be used to describe a multiplexer built upon
> several i2c isolators having an enable pin (such as LTC4310). These
> isolators can need some time between their enable pin's assertion and
> the first i2c transfer.
> 
> Add a 'transition-delay-ms' property that indicates the delay to be
> respected before doing the first i2c transfer.
> 

That's quite limited hardware description, comparing to cover letter.
Please provide full description here, not in cover letter. This is the
binding, so the hardware part.

Anyway, this does not look like property of mux itself. If there is no
isolator, the mux would work fine, right?

Then why you are not adding this property to every possible bus and I2C
controller? I2C isolator could be placed there as well.

So just like RC binding, that's not a property of I2C mux. Maybe this
fits usage of GPIO RC / delay binding.

Best regards,
Krzysztof