Linux USB OTG: Difference between revisions

From Variscite Wiki
(Fix imx8mn-var-som dts file for new kernels)
(Fix imx8mm, imx8mq dts files for new kernels)
Line 13: Line 13:
For example:<br>
For example:<br>
Follow either the "Build the Linux kernel from source code" or "Customizing the Linux kernel" Wiki pages and edit the following device tree file:<br>
Follow either the "Build the Linux kernel from source code" or "Customizing the Linux kernel" Wiki pages and edit the following device tree file:<br>
{{#ifeq: {{#var:HARDWARE_NAME}}|DART-MX8M|{{#ifeq: {{#var:YOCTO_NAME}}|Morty|arch/arm64/boot/dts/variscite/imx8m-var-dart-common.dtsi|arch/arm64/boot/dts/freescale/fsl-imx8mq-var-dart-common.dtsi}}|{{#ifeq: {{#var:HARDWARE_NAME}}|DART-MX8M-MINI|arch/arm64/boot/dts/freescale/fsl-imx8mm-var-dart.dts for DART-MX8M-MINI, or arch/arm64/boot/dts/freescale/fsl-imx8mm-var-som.dts for VAR-SOM-MX8M-MINI|
{{#ifeq: {{#var:HARDWARE_NAME}}|DART-MX8M|{{#ifeq: {{#var:YOCTO_NAME}}|Morty|arch/arm64/boot/dts/variscite/imx8m-var-dart-common.dtsi|arch/arm64/boot/dts/freescale/{{#if: {{#var:DTB_PREFIX}} | {{#var:DTB_PREFIX}}.dtsi | fsl-imx8mq-var-dart-common.dtsi }}}}|{{#ifeq: {{#var:HARDWARE_NAME}}|DART-MX8M-MINI|arch/arm64/boot/dts/freescale/{{#if: {{#var:DTB_PREFIX}} | {{#var:DTB_PREFIX}}.dts | fsl-imx8mm-var-dart.dts }} for DART-MX8M-MINI, or arch/arm64/boot/dts/freescale/{{#if: {{#var:DTB_PREFIX}} | {{#var:DTB_PREFIX}}.dts | fsl-imx8mm-var-som.dts }} for VAR-SOM-MX8M-MINI|
{{#ifeq: {{#var:HARDWARE_NAME}}|DART-MX8M-PLUS|arch/arm64/boot/dts/freescale/imx8mp-var-dart.dts for DART-MX8M-PLUS, or arch/arm64/boot/dts/freescale/imx8mp-var-som.dts for VAR-SOM-MX8M-PLUS|
{{#ifeq: {{#var:HARDWARE_NAME}}|DART-MX8M-PLUS|arch/arm64/boot/dts/freescale/imx8mp-var-dart.dts for DART-MX8M-PLUS, or arch/arm64/boot/dts/freescale/imx8mp-var-som.dts for VAR-SOM-MX8M-PLUS|
{{#ifeq: {{#var:HARDWARE_NAME}}|VAR-SOM-MX8M-NANO|freescale/{{#if: {{#var:DTB_PREFIX}} | {{#var:DTB_PREFIX}}.dts | fsl-imx8mn-var-som.dts }}}}}}}}}} <br>
{{#ifeq: {{#var:HARDWARE_NAME}}|VAR-SOM-MX8M-NANO|freescale/{{#if: {{#var:DTB_PREFIX}} | {{#var:DTB_PREFIX}}.dts | fsl-imx8mn-var-som.dts }}}}}}}}}} <br>

Revision as of 16:59, 8 June 2021

DART-MX8M 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 DART-MX8M custom 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-imx8mq-var-dart-common.dtsi

&usb_dwc3_0 {
	status = "okay";
	extcon = <&typec_ptn5150>;
-	dr_mode = "otg";
+	dr_mode = "host";
};

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/usb@38100000/dwc3/dr_mode; echo

Using the USB OTG port under Linux

As host (default)

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, a serial gadget called g_serial, etc.

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 type-C connector or use type-C to type-A adapter.
In order to use it as a peripheral and connect it to a PC, for example, a cable with a type-C plug on one end and a Standard-A plug on the other is needed.