linux-kernel - Re: [PATCH v5 1/2] ARM: dts: imx6: Add support for Toradex Apalis iMX6Q/D SoM

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Date:   Mon, 29 Aug 2016 16:28:50 +0300
From:   Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
To:     Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     Lucas Stach <l.stach@...gutronix.de>,
        Russell King <linux@....linux.org.uk>,
        Sascha Hauer <kernel@...gutronix.de>,
        Petr Štetiar <ynezz@...e.cz>,
        Fabio Estevam <festevam@...il.com>,
        Kumar Gala <galak@...eaurora.org>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Stefan Agner <stefan@...er.ch>,
        Joshua Clayton <stillcompiling@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Shawn Guo <shawnguo@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/2] ARM: dts: imx6: Add support for Toradex Apalis
 iMX6Q/D SoM

Hi Marcel,

On 02/05/2016 06:12 PM, Marcel Ziswiler wrote:
> From: Petr Štetiar <ynezz@...e.cz>
>
> Signed-off-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
> Signed-off-by: Petr Štetiar <ynezz@...e.cz>
> Reviewed-by: Stefan Agner <stefan@...er.ch>
> ---
>

because the change is in mainline now below is kind of out of date
information, but you may find it helpful.

[snip]

> - fixed HDMI DDC (requires GPIO-based bitbanging I2C to be enabled)

This is not needed.

[snip]

> +	/* DDC_I2C: I2C2_SDA/SCL on MXM3 205/207 */
> +	i2cddc: i2c@0 {
> +		compatible = "i2c-gpio";
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&pinctrl_i2c_ddc>;
> +		gpios = <&gpio3 16 GPIO_ACTIVE_HIGH /* sda */
> +			 &gpio2 30 GPIO_ACTIVE_HIGH /* scl */
> +			>;
> +		i2c-gpio,delay-us = <2>;	/* ~100 kHz */
> +		status = "disabled";
> +	};
> +

This is not needed.

[snip]

> +	pinctrl_i2c_ddc: gpioi2cddcgrp {
> +		fsl,pins = <
> +			/* DDC bitbang */
> +			MX6QDL_PAD_EIM_EB2__GPIO2_IO30 0x1b0b0
> +			MX6QDL_PAD_EIM_D16__GPIO3_IO16 0x1b0b0
> +		>;
> +	};
> +

Practically you don't need this overcomplicated GPIO-based bitbanging
to emulate I2C, because the DW HDMI controller has a reduced I2C
controller on board, you may take a look at its support published here:

    http://www.spinics.net/lists/dri-devel/msg116308.html

To utilize it the pads should be set to HDMI function instead of
I2C or GPIO.

--
With best wishes,
Vladimir