linux-kernel - Re: [PATCH 1/3] dt-bindings: i2c: add optional mul-value property to binding

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Message-ID: <20190430063822.dk5nerqa2m36ua6x@pengutronix.de>
Date:   Tue, 30 Apr 2019 08:38:22 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Chuanhua Han <chuanhua.han@....com>
Cc:     robh+dt@...nel.org, mark.rutland@....com, shawnguo@...nel.org,
        s.hauer@...gutronix.de, leoyang.li@....com,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        kernel@...gutronix.de, linux-imx@....com, festevam@...il.com,
        wsa+renesas@...g-engineering.com, eha@...f.com,
        linux@...pel-privat.de, sumit.batra@....com,
        l.stach@...gutronix.de, peda@...ntia.se
Subject: Re: [PATCH 1/3] dt-bindings: i2c: add optional mul-value property to
 binding

On Tue, Apr 30, 2019 at 12:32:40PM +0800, Chuanhua Han wrote:
> NXP Layerscape SoC have up to three MUL options available for all
> divider values, we choice of MUL determines the internal monitor rate
> of the I2C bus (SCL and SDA signals):
> A lower MUL value results in a higher sampling rate of the I2C signals.
> A higher MUL value results in a lower sampling rate of the I2C signals.
> 
> So in Optional properties we added our custom mul-value property in the
> binding to select which mul option for the device tree i2c controller
> node.
> 
> Signed-off-by: Chuanhua Han <chuanhua.han@....com>
> ---
>  Documentation/devicetree/bindings/i2c/i2c-imx.txt | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-imx.txt b/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> index b967544590e8..ba8e7b7b3fa8 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> @@ -18,6 +18,9 @@ Optional properties:
>  - sda-gpios: specify the gpio related to SDA pin
>  - pinctrl: add extra pinctrl to configure i2c pins to gpio function for i2c
>    bus recovery, call it "gpio" state
> +- mul-value: NXP Layerscape SoC have up to three MUL options available for
> +all I2C divider values, it describes which MUL we choose to use for the driver,
> +the values should be 1,2,4.

Indention is broken.

I wonder why this needs to be configurable on a per-machine/device
level. What is the trade-off?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |