linux-kernel - Re: [PATCH v3 0/3] i2c: mux: gpio: Add 'settle-time-us' property

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Message-ID: <135887c3-4eac-4397-bad9-6bd0a03283de@bootlin.com>
Date: Wed, 3 Jul 2024 11:35:22 +0200
From: Bastien Curutchet <bastien.curutchet@...tlin.com>
To: 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 <herve.codina@...tlin.com>,
 Christopher Cordahi <christophercordahi@...ometrics.ca>
Subject: Re: [PATCH v3 0/3] i2c: mux: gpio: Add 'settle-time-us' property

Hi all,

On 6/17/24 14:08, Bastien Curutchet wrote:
> Hi all,
> 
> The i2c-gpio-mux can be used to describe a multiplexer built upon
> several i2c isolators having an enable pin (such as LTC4310):
> 
>   +---------------+                     +------+  +------+
>   | +-----------+ |                     | dev  |  | dev  |
>   | | GPIO_EN_A |-|-----------|         +------+  +------+
>   | +-----------+ |     +-----+---+         |         |
>   |               |  |--| isol. A |---------+---------+
>   |     +-----+   |  |  +---------+
>   | SOC | I2C |---|--|
>   |     +-----+   |  |  +---------+
>   |               |  |--| isol. B |------+---------+---------+
>   | +-----------+ |     +-----+---+      |         |         |
>   | | GPIO_EN_B |-|-----------|      +------+  +------+  +------+
>   | +-----------+ |                  | dev  |  | dev  |  | dev  |
>   +---------------+                  +------+  +------+  +------+
> 
> These isolators often need some time between their enable pin's
> assertion and the first i2c transfer. If the first i2c transfer
> happens before this enabling time is reached, transfer fails.
> 
> There is no available option to configure such a time in the
> i2c-gpio-mux driver.
> 
> Add a optional property in the bindings called 'transition-delay-us'.
> If present, driver waits for this delay every time a new bus is
> selected, i.e. before returning from the bus_select() callback.
> 
> Changes in v2:
>   * Rewrite bindings' commit log
>   * Express the 'transition delay' in us instead of ms
> 
> Changes in v3:
>   * Rename DT property to 'settle-time-us'
>   * Use fsleep instead of udelay
> 
> [v1] : https://lore.kernel.org/all/20240527113908.127893-1-bastien.curutchet@bootlin.com/
> [v2] : https://lore.kernel.org/all/20240529091739.10808-1-bastien.curutchet@bootlin.com/
> 

I don't think I've received any feedback since the bindings were 
reviewed by Krzysztof. Has anyone had a chance to look at this V3 
iteration yet?


Best regards,
Bastien