linux-kernel - Re: [RFC v2 2/4] dt-bindings: i2c: mux: demux-pinctrl: add bindings

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Date:	Thu, 07 Jan 2016 17:56:38 +0100
From:	Jan Lübbe <jlu@...gutronix.de>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	linux-i2c@...r.kernel.org, linux-sh@...r.kernel.org,
	Magnus Damm <magnus.damm@...il.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Subject: Re: [RFC v2 2/4] dt-bindings: i2c: mux: demux-pinctrl: add bindings

Hi Wolfram,

On Mi, 2016-01-06 at 14:51 +0100, Wolfram Sang wrote:
[...]
> +Required properties:
> +- compatible: "i2c-demux-pinctrl"
> +- i2c-parent: List of phandles of I2C masters available for selection. The first
> +	      one will be used as default.
> +- i2c-bus-name: The name of this bus. Also needed as pinctrl-name for the I2C
> +		parents.
[...]
> +	i2chdmi: i2c@8 {
> +		compatible = "i2c-demux-pinctrl";
> +		i2c-parent = <&gpioi2c>, <&iic2>, <&i2c2>;
> +		i2c-bus-name = "i2c-hdmi";
> +		#address-cells = <1>;
> +		#size-cells = <0>;
[...]
> +	gpioi2c: i2c@9 {
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		compatible = "i2c-gpio";
[...]
> +&i2c2	{
> +	pinctrl-0 = <&i2c2_pins>;
> +	pinctrl-names = "i2c-hdmi";
> +
> +	clock-frequency = <100000>;
> +};
[...]
> +&iic2	{
> +	pinctrl-0 = <&iic2_pins>;
> +	pinctrl-names = "i2c-hdmi";
> +
> +	clock-frequency = <100000>;
> +};
[...]

It seems that the demux-pinctrl driver reconfigures the pinctrl settings
for the parent devices. I would have expected to have alternative
pinctrl state on the demux node support switching the same external pins
between the different controllers. Wouldn't it be possible to have
pinctrl conflicts between &i2c2_pins and &iic2_pins otherwise?

Regards,
Jan
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