Crash while disconnecting device from USB

[pdunaj]

Describe the bug
Device starts as connected, disconnect it promptly.

ASSERTION FAIL [m_drv_state == NRFX_DRV_STATE_POWERED_ON] @ /home/padu/work/fw-nrfconnect-zephyr/ext/hal/nordic/nrfx/drivers/src/nrfx_usbd.c:1865:

To Reproduce
This is a race. Will add more info in the comment.
Start with the device connected. Just after booting up disconnect the device.

Expected behavior
Device must not crash.

Impact
Probably showstopper although it is not easy to replicate (so far happened once).

Screenshots or console output
Assert above.

Environment (please complete the following information):
rev:{{e21d7cc}}
Replicated using older revision but the bug is still there.

[pdunaj]

I was unable to replicate it while testing today but I see how this can be triggered.
usb_dc_nrfx_power_event_callback is being called with event from hw, set the state and then submits the work.

usb_dc_nrfx_power_event_callback is called from an interrupt context while work is executed from a workqueue thread.

There are two cases that can lead to the assert (situation where we detached while not being attached). Common part is that device starts with USB detached, then device is attached and work is submitted. Now the cases:

1. Before work is executed device detaches. Work will execute with detached state and call nrfx detach again.
2. While work executes device detaches. In this case state will change while we process.

In both cases we should get an assert.

Hi @pawelzadrozniak , could you review this part. I think we need to handle the state check directly in usb_dc_nrfx_power_event_callback (e.g. if state is not changed do not schedule work) or enqueue all events and process them in the same order as were received from HW.