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 DART-MX8M 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 | 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> | ||
<br> | <br> | ||
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> | ||
arch/arm64/boot/dts/variscite/imx8m-var-dart-common.dtsi<br> | arch/arm64/boot/dts/{{#ifeq: {{#var:HARDWARE_NAME}} | DART-MX8M | {{#ifeq: {{#var:YOCTO_NAME}} | Morty |variscite/imx8m-var-dart-common.dtsi|freescale/fsl-imx8mq-var-dart-common.dtsi}} | freescale/fsl-imx8mm-var-dart.dts}} <br> | ||
{{#ifeq: {{#var:HARDWARE_NAME}} | DART-MX8M | | |||
<syntaxhighlight lang="diff"> | <syntaxhighlight lang="diff"> | ||
&usb_dwc3_0 { | &usb_dwc3_0 { | ||
| Line 15: | Line 21: | ||
+ dr_mode = "host"; | + dr_mode = "host"; | ||
}; | }; | ||
</syntaxhighlight> | |||
| | |||
<syntaxhighlight lang="diff"> | |||
&usbotg1 { | |||
- dr_mode = "otg"; | |||
+ dr_mode = "host"; | |||
picophy,pre-emp-curr-control = <3>; | |||
picophy,dc-vol-level-adjust = <7>; | |||
status = "okay"; | |||
}; | |||
</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> | ||
<br> | <br> | ||
| Line 32: | Line 49: | ||
Example using the g_mass_storage module to expose the root partition on eMMC to a PC while booting from recovery SD card:<br> | Example using the g_mass_storage module to expose the root partition on eMMC to a PC while booting from recovery SD card:<br> | ||
Connect a type-C plug to Standard-A plug cable between the board and a PC, and run the following on the board: | 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/ | # umount /dev/{{#var:EMMC_ROOTFS_DEV}}p1 | ||
# modprobe g_mass_storage file=/dev/ | # modprobe g_mass_storage file=/dev/{{#var:EMMC_ROOTFS_DEV}}p1 | ||
The partition should be loaded on the PC as a mass storage device. | The partition should be loaded on the PC as a mass storage device. | ||
Revision as of 12:04, 27 February 2019
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-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@38100000/dwc3/dr_mode; echo
Using the USB OTG port under Linux
As host (default)
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/p1 # modprobe g_mass_storage file=/dev/p1
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.