Hi Felipe,

I hope you are doing well. My team and I are frequently experiencing an
issue with the dwc3 in our CherryTrail SoC where we encounter an LFPS
Polling timeout while our device is being enumerated.

We configured the dwc3 as an ethernet gadget using configfs and the ecm
and RNDIS functions. The dwc3 transitions to U3 after configuration as
expected. Only once we connect our device to a USB host do we see the
link state transition to Polling. We are assuming LFPS Polling times
out because the link_state file in debugfs shows the link has
transitioned to compliance mode only after entering LFPS.Polling, and we
recently learned that compliance mode is triggered by a timeout during
LFPS.Polling.

This issue is not 100% reproducible, but is occuring rather frequently
at the moment. We're unsure of the root cause of the issue as well. One
culprit might be the USB SuperSpeed Redriver we use in our design.

We would like to disable compliance mode in the meantime to allow other
team members to continue developing and testing USB device mode features
while we dig into the root cause of the issue. Is there a proper way to
disable compliance mode entirely?

If not, is there some mechanism we could implement to reset the
dwc3 when we enter compliance mode? I attempted some sort of mechanism
to reset the link state, but it does not seem to help the issue. I've
attached my patch and the trace events for my attempted workaround to
this email. My initial approach was to transition the link from
Compliance -> SS.Disabled -> Rx.Detect when we detect we've entered
compliance mode. The traces show that the dwc3 just enters LFPS.Polling
and subsequently enters compliance mode, despite the link being reset.

Do you have any ideas on how we might work around compliance mode in the
meantime?

Thanks in advance for your input!

Cheers,
Rob Weber