linux-kernel - Re: [PATCH 03/10] arm64: dts: imx8mp-skov: use I2C5 for DDC

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Message-ID: <a30baba6-6252-4c69-b6a7-e4099e823920@pengutronix.de>
Date: Thu, 19 Dec 2024 18:43:56 +0100
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: Frank Li <Frank.li@....com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>, Oleksij Rempel
 <o.rempel@...gutronix.de>, devicetree@...r.kernel.org, imx@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/10] arm64: dts: imx8mp-skov: use I2C5 for DDC

Hello Frank,

On 19.12.24 18:34, Frank Li wrote:
> On Thu, Dec 19, 2024 at 08:25:27AM +0100, Ahmad Fatoum wrote:
>> The HDMI DDC pads can be muxed either to an i.MX I2C controller or
>> to a limited I2C controller within the Designware HDMI bridge.
>>
>> So far we muxed the pads to the HDMI bridge, but the i.MX I2C controller
>> is the better choice:
> 
> Switch to the i.MX I2C controller because
> 
>>
>>   - We use DDC/CI commands for display brightness configuration, but the
>>     Linux driver refuses[1] transfers to/from address 0x37, because the
>>     controller doesn't support multi-byte requests.
> 
>       Designware HDMI Limited I2C controller doesn't support multi-byte
> requests and display brightness configuration by DDC/CI command need it.
> 
>>
>>   - The driver doesn't support I2C bus recovery, but we need that,
>>     because some HDMI panels used with the board can be flaky.
> 
>       Designware HDMI Limited I2C controller doesn't support I2C bus
> recovery.
> 
>>
>> As the i.MX I2C controller doesn't have either of these limitations,
>> let's make use of it instead.
> 
> Reduntant. can be removed.

Sorry, I am very much open to review feedback, but I fail to see how
your subjective take improves things.

Thanks,
Ahmad




> 
> Frank
>>
>> [1]: https://lore.kernel.org/all/20190722181945.244395-1-mka@chromium.org/
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
>> ---
>>  .../boot/dts/freescale/imx8mp-skov-revb-hdmi.dts   | 26 ++++++++++++++++++++--
>>  1 file changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/freescale/imx8mp-skov-revb-hdmi.dts b/arch/arm64/boot/dts/freescale/imx8mp-skov-revb-hdmi.dts
>> index c1ca69da3cb8..206116be8166 100644
>> --- a/arch/arm64/boot/dts/freescale/imx8mp-skov-revb-hdmi.dts
>> +++ b/arch/arm64/boot/dts/freescale/imx8mp-skov-revb-hdmi.dts
>> @@ -9,12 +9,34 @@ / {
>>  	compatible = "skov,imx8mp-skov-revb-hdmi", "fsl,imx8mp";
>>  };
>>
>> +&i2c5 {
>> +	pinctrl-names = "default", "gpio";
>> +	pinctrl-0 = <&pinctrl_i2c5>;
>> +	pinctrl-1 = <&pinctrl_i2c5_gpio>;
>> +	scl-gpios = <&gpio3 26 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
>> +	sda-gpios = <&gpio3 27 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
>> +	clock-frequency = <100000>;
>> +	status = "okay";
>> +};
>> +
>>  &iomuxc {
>>  	pinctrl_hdmi: hdmigrp {
>>  		fsl,pins = <
>> -			MX8MP_IOMUXC_HDMI_DDC_SCL__HDMIMIX_HDMI_SCL		0x1c3
>> -			MX8MP_IOMUXC_HDMI_DDC_SDA__HDMIMIX_HDMI_SDA		0x1c3
>>  			MX8MP_IOMUXC_HDMI_HPD__HDMIMIX_HDMI_HPD			0x19
>>  		>;
>>  	};
>> +
>> +	pinctrl_i2c5: i2c5grp {
>> +		fsl,pins = <
>> +			MX8MP_IOMUXC_HDMI_DDC_SCL__I2C5_SCL			0x400001c2
>> +			MX8MP_IOMUXC_HDMI_DDC_SDA__I2C5_SDA			0x400001c2
>> +		>;
>> +	};
>> +
>> +	pinctrl_i2c5_gpio: i2c5gpiogrp {
>> +		fsl,pins = <
>> +			MX8MP_IOMUXC_HDMI_DDC_SCL__GPIO3_IO26			0x400001c2
>> +			MX8MP_IOMUXC_HDMI_DDC_SDA__GPIO3_IO27			0x400001c2
>> +		>;
>> +	};
>>  };
>>
>> --
>> 2.39.5
>>
> 


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