Re: [PATCH v5 5/7] arm64: dts: imx8dxl-evk: Add onboard GPIO mux controller

From: Frank Li <Frank.Li@nxp.com>

Add a GPIO mux controller to describe the onboard signal multiplexer.
Previously, the device tree relied on the hardware reset defaults to
select the mux state. Now that the kernel supports the pinctrl-multiplexer
framework, describe the onboard mux explicitly and let the kernel configure
the required routing.

Prepare for additional device tree overlays that require different mux
configurations.

Remove the regulator-m2uart1sel node, which incorrectly modeled the board
mux as a regulator.

There are no backward compatibility concerns, as the affected functions
(lpuart1 for Bluetooth, spi3, and m4_lpuart) are not used by existing other
users such as U-Boot.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v4
- add idle-state = <1> (sashiko AI)
- ref to spi0_fun for sai0
---
 arch/arm64/boot/dts/freescale/imx8dxl-evk.dts | 80 +++++++++++++++++++++++----
 1 file changed, 68 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8dxl-evk.dts b/arch/arm64/boot/dts/freescale/imx8dxl-evk.dts
index 71eff3efa6d32..f21ac208bf00e 100644
--- a/arch/arm64/boot/dts/freescale/imx8dxl-evk.dts
+++ b/arch/arm64/boot/dts/freescale/imx8dxl-evk.dts

@@ -97,14 +97,70 @@ vdev0buffer: vdev0buffer@90400000 {
 		};
 	};
 
-	m2_uart1_sel: regulator-m2uart1sel {
-		compatible = "regulator-fixed";
-		regulator-min-microvolt = <3300000>;
-		regulator-max-microvolt = <3300000>;
-		regulator-name = "m2_uart1_sel";
-		gpio = <&pca6416_1 6 GPIO_ACTIVE_HIGH>;
-		enable-active-high;
-		regulator-always-on;
+	m4_debug_mux: mux-controller-0 {
+		compatible = "gpio-mux";
+		#mux-control-cells = <0>;
+		#mux-state-cells = <1>;
+		idle-state = <1>;
+		mux-gpios = <&pca6416_1 3 GPIO_ACTIVE_HIGH>;
+	};
+
+	spi3_mux: mux-controller-1 {
+		compatible = "gpio-mux";
+		#mux-control-cells = <0>;
+		#mux-state-cells = <1>;
+		idle-state = <1>;
+		mux-gpios = <&pca6416_1 4 GPIO_ACTIVE_HIGH>;
+	};
+
+	uart1_mux: mux-controller-2 {
+		compatible = "gpio-mux";
+		#mux-control-cells = <0>;
+		#mux-state-cells = <1>;
+		mux-gpios = <&pca6416_1 6 GPIO_ACTIVE_HIGH>;
+	};
+
+	spi0_mux: mux-controller-3 {
+		compatible = "gpio-mux";
+		#mux-control-cells = <0>;
+		#mux-state-cells = <1>;
+		mux-gpios = <&pca6416_1 7 GPIO_ACTIVE_HIGH>;
+	};
+
+	pinctrl-gpiomux {
+		compatible = "pinctrl-multiplexer";
+
+		m4_debug_fun: cm4-uart-grp {
+			mux-states = <&m4_debug_mux 1>;
+		};
+
+		spi0_fun: spi0-grp {
+			mux-states = <&spi0_mux 1>;
+		};
+
+		spi3_fun: spi3-grp {
+			mux-states = <&spi3_mux 1>;
+		};
+
+		uart1_fun: uart1-grp {
+			mux-states = <&uart1_mux 1>;
+		};
+
+		lcd_0_fun: lcd0-grp {
+			mux-states = <&spi0_mux 0>;
+		};
+
+		lcd_1_fun: lcd1-grp {
+			mux-states = <&spi3_mux 0>;
+		};
+
+		lcd_2_fun: lcd2-grp {
+			mux-states = <&uart1_mux 0>;
+		};
+
+		lcd_3_fun: lcd3-grp {
+			mux-states = <&m4_debug_mux 0>;
+		};