# Read the DWC3 debugfs entries

The DWC3 controller exposes its state through the debugfs directory
`/d/usb/a600000.dwc3`.

Read the debugfs entries to inspect the controller registers, link
state, operating mode, and endpoint queues while you debug the USB
interface.

The following table lists the DWC3 debugfs entries, their read/write
access, and their contents.

| Filename | Read/Write | Comments |
| --- | --- | --- |
| `regdump` | R | Outputs the DWC3 controller registers. |
| `link_state` | R/W | Read outputs the USB link state; write changes the USB link state. |
| `mode` | R/W | Read outputs the current USB operating mode (host or device); write sets<br>the USB controller registers to the mode but doesn’t affect the software<br>state machine. |
| `testmode` | R/W | Read outputs the current test mode, if any; write sets the test mode. |
| `descriptor_fetch_queue` | R | Outputs the remaining space for the IN/OUT endpoint’s descriptor fetch<br>FIFO. |
| `event_queue` | R | Outputs the remaining space for the endpoint’s event queue. |
| `rx_fifo_queue` | R | Outputs the remaining space for the endpoint’s Rx FIFO queue (not valid<br>for IN endpoints). |
| `rx_info_queue` | R | Outputs the remaining space for the endpoint’s Rx INFO queue (not valid<br>for IN endpoints). |
| `rx_request_queue` | R | Outputs the remaining space for the endpoint’s Rx request queue (not<br>valid for IN endpoints). |
| `transfer_type` | R | Outputs the endpoint type, for example BULK, INTERRUPT, or ISOC. |
| `trb_ring` | R | Prints the transfer request block (TRB) ring for the endpoint and its<br>pending TRBs. |
| `tx_fifo_queue` | R | Outputs the remaining space for the endpoint’s Tx FIFO queue (not valid<br>for OUT endpoints). |
| `tx_request_queue` | R | Outputs the remaining space for the endpoint’s Tx request queue (not<br>valid for OUT endpoints). |

## Related

- [Enable full USB logs in UEFI](https://docs.qualcomm.com/doc/80-A0399-8/topic/enable-full-usb-logs-uefi.html)
- [Debug UEFI USB with serial logs and JTAG](https://docs.qualcomm.com/doc/80-A0399-8/topic/debug-uefi-usb-serial-jtag.html)
- [Troubleshoot the USB interface](https://docs.qualcomm.com/doc/80-A0399-8/topic/troubleshoot-usb.html)

Last Published: Sep 17, 2026

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