linux-kernel - Re: [PATCH] arm64: dts: imx8mp: Enable HDMI on i.MX8MP DHCOM PDK2 and PDK3

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Message-ID: <fa01ef26-d4d4-4c62-9c12-1f8bed1cfdab@denx.de>
Date: Thu, 16 May 2024 13:44:08 +0200
From: Marek Vasut <marex@...x.de>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>,
 Francesco Dolcini <francesco@...cini.it>
Cc: Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 devicetree@...r.kernel.org, Shawn Guo <shawnguo@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>, linux-kernel@...r.kernel.org,
 imx@...ts.linux.dev, kernel@...electronics.com,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Fabio Estevam
 <festevam@...il.com>, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64: dts: imx8mp: Enable HDMI on i.MX8MP DHCOM PDK2 and
 PDK3

On 5/16/24 1:36 PM, Ahmad Fatoum wrote:
> Hello Marek,

Hi,

> On 16.05.24 13:14, Marek Vasut wrote:
>> On 5/16/24 10:00 AM, Francesco Dolcini wrote:
>>> Hello Marek,
>>
>> Hi,
>>
>>> On Tue, May 14, 2024 at 03:06:42AM +0200, Marek Vasut wrote:
>>>> Enable HDMI output on i.MX8MP DHCOM PDK2 and PDK3. The I2C5 on PDK2 and
>>>> I2C mux port 1 on PDK3 respectively are used in regular I2C mode instead
>>>> of HDMI DDC mode to permit connection of other I2C devices on those buses.
>>>
>>> Are you able to read the HDMI EDID with such configuration? I have the
>>> patch ready for verdin imx8mp, I just did not have time to figure out
>>> this last details.
>>
>> Yes with ddc-i2c-bus in hdmi_tx{} node, no with ddc-i2c-bus in connector node. Maybe that's what you're running into ? The DW HDMI core needs the ddc-i2c-bus property in hdmi_tx{} node if you use non-native I2C bus for the DDC channel.
> 
> What benefit does the hdmi-connector provide over just omitting it?
> Just for documentation purposes?

I was under the impression describing the hardware in DT in full was the 
best practice (TM), hence it is in full here.