linux-kernel - Re: [PATCH 1/2] dt-bindings: i2c: Add MediaTek i2c AC timing binding

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Date:   Wed, 26 Jun 2019 15:39:41 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Qii Wang <qii.wang@...iatek.com>
Cc:     linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        leilk.liu@...iatek.com, matthias.bgg@...il.com, robh+dt@...nel.org
Subject: Re: [PATCH 1/2] dt-bindings: i2c: Add MediaTek i2c AC timing binding

Hi,

On Tue, Jun 11, 2019 at 04:11:54PM +0800, Qii Wang wrote:
> Add i2c AC timing binding to binding file. It can give the AC
> timing parameters to meet I2C specification at different speed.
> 
> Signed-off-by: Qii Wang <qii.wang@...iatek.com>

I think this is a too specific 1:1 mapping of your register set into DT
world. We already have these generic parameters:

- clock-frequency
        frequency of bus clock in Hz.

- i2c-scl-falling-time-ns
        Number of nanoseconds the SCL signal takes to fall; t(f) in the I2C
        specification.

- i2c-scl-internal-delay-ns
        Number of nanoseconds the IP core additionally needs to setup SCL.

- i2c-scl-rising-time-ns
        Number of nanoseconds the SCL signal takes to rise; t(r) in the I2C
        specification.

- i2c-sda-falling-time-ns
        Number of nanoseconds the SDA signal takes to fall; t(f) in the I2C
        specification.

(check Documentation/devicetree/bindings/i2c/i2c.txt)

Can't you use those to derive your values from that? Which ones are you missing
if not?

Regards,

   Wolfram

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