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

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Message-Id: <20241219-skov-dt-updates-v1-3-38bf80dc22df@pengutronix.de>
Date: Thu, 19 Dec 2024 08:25:27 +0100
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: 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>
Cc: devicetree@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 kernel@...gutronix.de, Ahmad Fatoum <a.fatoum@...gutronix.de>
Subject: [PATCH 03/10] arm64: dts: imx8mp-skov: use I2C5 for DDC

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:

  - 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.

  - The driver doesn't support I2C bus recovery, but we need that,
    because some HDMI panels used with the board can be flaky.

As the i.MX I2C controller doesn't have either of these limitations,
let's make use of it instead.

[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