USB OTG¶

Configuring the USB OTG port under Linux¶

By default, the USB OTG port is configured as OTG in the device tree, and a USB type-C receptacle is assembled on the Symphony carrier board.
To use it as host only or peripheral only, you need to change the value of the dr_mode property under the USB node in the device tree.
dr_mode: One of "host", "peripheral", or "otg". Defaults to "otg"

For example:
Follow either the "Build the Linux kernel from source code" or "Customizing the Linux kernel" Wiki pages and edit the following device tree file:
arch/arm64/boot/dts/freescale/fsl-imx8qxp-var-som-common.dtsi

&usbotg3 {
-   dr_mode = "otg";
+   dr_mode = "host";
    extcon = <&typec_ptn5150>;
    status = "okay";
};

If you build the kernel manually from source code, you should build only the device trees and copy them to your SD card or eMMC.

Note: You can read the current dr_mode value on a running target by executing the following command:

cat /sys/firmware/devicetree/base/usb3@5b110000/dr_mode;

Using the USB OTG port under Linux¶

As host (default)¶

Refer to USB host

As peripheral¶

In order to use the board as a peripheral, an appropriate module needs to be loaded.
For example, there is an Ethernet gadget module called g_ether, a mass storage gadget called g_mass_storage, and a serial gadget called g_serial.

Example using the g_mass_storage module to expose the root partition on eMMC to a PC while booting from recovery SD card:
Connect a type-C plug to Standard-A plug cable between the board and a PC, and run the following on the board:

umount /dev/mmcblk0p1
modprobe g_mass_storage file=/dev/mmcblk0p1

The partition should be loaded on the PC as a mass storage device.

As OTG¶

With OTG, the board can be either a host or a peripheral.
In order to use it as a host and connect a peripheral (e.g. a USB flash drive) to it, either use a peripheral with a type-C connector or use a type-C to type-A adapter.
In order to use it as a peripheral and connect it to a PC, a cable with a type-C plug on one end and a Standard-A plug on the other is needed.