Linux USB OTG: Difference between revisions

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= Configuring the USB OTG port under Linux =
= 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.<br>
By default, the USB OTG port is configured as OTG in the device tree, and a USB type-C receptacle is assembled on the {{#var:HARDWARE_NAME}} custom board.<br>
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.<br>
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.<br>
dr_mode: One of "host", "peripheral" or "otg". Defaults to "otg"<br>
dr_mode: One of "host", "peripheral" or "otg". Defaults to "otg"<br>
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{{#ifeq: {{#var:HARDWARE_NAME}} | DART-MX8M |
{{#ifeq: {{#var:HARDWARE_NAME}} | DART-MX8M |
<syntaxhighlight lang="diff">
&usb_dwc3_0 {
status = "okay";
extcon = <&typec_ptn5150>;
- dr_mode = "otg";
+ dr_mode = "host";
};
</syntaxhighlight>
|
{{#ifeq: {{#var:HARDWARE_NAME}} | DART-MX8M-PLUS |
<syntaxhighlight lang="diff">
<syntaxhighlight lang="diff">
&usb_dwc3_0 {
&usb_dwc3_0 {
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};
};
</syntaxhighlight>
</syntaxhighlight>
}}
}}}}


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.<br>
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.<br>
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<pre>
<pre>
# cat /sys/firmware/devicetree/base/usb@38100000/dwc3/dr_mode; echo
# cat /sys/firmware/devicetree/base/usb@38100000/dwc3/dr_mode; echo
</pre>
|
{{#ifeq: {{#var:HARDWARE_NAME}} | DART-MX8M-PLUS |
<pre>
# cat /sys/firmware/devicetree/base/usb@32f10100/dwc3@38100000/dr_mode; echo
</pre>
</pre>
|
|
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# cat /sys/firmware/devicetree/base/usb@32e40000/dr_mode; echo
# cat /sys/firmware/devicetree/base/usb@32e40000/dr_mode; echo
</pre>
</pre>
}}
}}}}


= Using the USB OTG port under Linux =
= Using the USB OTG port under Linux =

Revision as of 09:00, 16 November 2020


VAR-SOM-MX6 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 VAR-SOM-MX6 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-imx8mm-var-dart.dts

&usbotg1 {
-	dr_mode = "otg";
+	dr_mode = "host";
	picophy,pre-emp-curr-control = <3>;
	picophy,dc-vol-level-adjust = <7>;
	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/usb@32e40000/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.