[QUESTION] ANX7688 USB Type-C driver issues on CM4 Yocto project

Hello Yocto community,

I am currently working on a Yocto project to create a Linux system for an
electronic board based on a Raspberry Pi Compute Module 4 (CM4). Many
components are integrated on the board to provide various features.

One of these features is the *ANX7688*, which manages the board’s USB
Type-C port. We need to support *video output* through this port, but also
allow *USB flash drive access*. The Type-C port is connected to the
ANX7688, and if a non-video device is connected, it switches to the *VL805* USB
controller.

The *ANX7688 driver is not included in the Linux mainline*, so I adapted
the driver from the PinePhone project for our board. The driver *loads
correctly*, and the *work function executes properly*, displaying the state
of the three main pins: Cable Detect, Power Enable, and Reset.

*Observed issues:*

   -

   When I plug in a USB flash drive, the ANX7688 powers on and the Cable
   Detect pin does not change, but the *PD negotiation reports a 0 mA limit*,
   so communication with the USB device does not occur.
   -

   Occasionally, when removing the USB flash drive, *Cable Detect remains
   high (1)* even though no device is connected to the Type-C port.
   -

   Many PD messages are exchanged, but *nothing happens when connecting a
   monitor* to the Type-C port.

*Relevant Device Tree overlay:*

/dts-v1/;
/plugin/;

/ {
    compatible = "brcm,bcm2711";

    fragment@0 {
        target = <&usb>;
        __overlay__ {
            dr_mode = "otg";
            usb-role-switch;
            role-switch-default-mode = "host";
            status = "okay";
        };
    };

    fragment@1 {
        target = <&i2c1>;
        __overlay__ {
            #address-cells = <1>;
            #size-cells = <0>;

            gpio_expander: gpio_expander@23 {
                compatible = "nxp,pcal6524";
                status = "okay";
                reg = <0x23>;
                gpio-controller;
                #gpio-cells = <2>;
                interrupt-parent = <&gpio>;
                interrupts = <6 2>;
                interrupt-controller;
                #interrupt-cells = <2>;
                int-gpios = <&gpio 6 0>;

                gpio-line-names =
                    "CMD_MOSFET_ALIM",
                    "RS_BUS_RESET",
                    "CAN_BUS_RESET",
                    "OI_GPIO",
                    "CAN_USER_RESET",
                    "RS_USER_RESET",
                    "CTRL_USB_SWITCH",
                    "5V_BORNIER_PG",
                    "BORNIER_EN",
                    "ANX7688_PE",
                    "ANX7688_CABLE_DET",
                    "ANX7688_RESET",
                    "STOR_Sensor4_Digital",
                    "ETOR1",
                    "STOR_Sensor1_Digital",
                    "ETOR2",
                    "ETOR4",
                    "STOR_Sensor2_Digital",
                    "ETOR3",
                    "STOR_Sensor3_Digital",
                    "STOR_CMD_1",
                    "STOR_CMD_2",
                    "STOR_CMD_3",
                    "STOR_CMD_4";
            };

            anx7688: anx7688@28 {
                compatible = "analogix,anx7688";
                reg = <0x28>;
                status = "okay";

                interrupt-parent = <&gpio>;
                interrupts = <45 8>;

                reset-gpios = <&gpio_expander 11 0>;
                enable-gpios = <&gpio_expander 9 0>;
                cabledet-gpios = <&gpio_expander 10 0>;

                source-caps = <0x26019032>;
                sink-caps = <0x2601912C>;

                vbus-supply = <&vdd_5v0_reg>;
                vbus_in-supply = <&power 6>;

                role-switch = <&usb>;
            };
        };
    };
};

I would greatly appreciate any guidance on the following:

   -

   Is my approach for integrating this non-mainline driver into Yocto
   correct?
   -

   Are there recommended steps or best practices for debugging USB
   Type-C/PD negotiation and video output on such hardware?

Thank you very much for your help!

Best regards,
Pavel