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

[Frank Li <Frank.li@nxp.com>]

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.

Frank
>
> [1]: https://lore.kernel.org/all/20190722181945.244395-1-mka@chromium.org/
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.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
>