Hi Rob, Rob Weber <rob@xxxxxxxxxxx> writes: > 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? That's not something that can be done, unfortunately. > 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. I think you would have to go through the entire Power On Reset sequence, but that's likely to be flakey. > Do you have any ideas on how we might work around compliance mode in the > meantime? We have a few quirk flags that may help. snps,u2exit_lfps_quirk comes to mind, but I suggest trying a few of them and see if any helps. All flags are described in Documentation/devicetree/bindings/usb/dwc3.txt > /* -------------------------------------------------------------------------- */ > # tracer: nop > # > # entries-in-buffer/entries-written: 220/220 #P:4 > # > # _-----=> irqs-off > # / _----=> need-resched > # | / _---=> hardirq/softirq > # || / _--=> preempt-depth > # ||| / delay > # TASK-PID CPU# |||| TIMESTAMP FUNCTION > # | | | |||| | | > <idle>-0 [003] ..s1 178.444339: dwc3_core: Tick! Checking for compliance mode > > <idle>-0 [003] d.s2 178.444352: dwc3_core: Compliance Mode detected. Attempting recovery routine > irq/23-dwc3-1115 [002] d..1 178.445380: dwc3_event: event (00140301): Link Change [SS.Disabled] > irq/23-dwc3-1115 [002] d..1 178.445826: dwc3_event: event (00150301): Link Change [RX.Detect] > irq/23-dwc3-1115 [002] d..1 178.445832: dwc3_event: event (00170301): Link Change [Polling] > <idle>-0 [003] ..s1 180.492293: dwc3_core: Tick! Checking for compliance mode > > <idle>-0 [003] d.s2 180.492306: dwc3_core: Compliance Mode detected. Attempting recovery routine > > irq/23-dwc3-1115 [002] d..1 180.493333: dwc3_event: event (00140301): Link Change [SS.Disabled] > irq/23-dwc3-1115 [002] d..1 180.493636: dwc3_event: event (00150301): Link Change [RX.Detect] > irq/23-dwc3-1115 [002] d..1 180.493641: dwc3_event: event (00170301): Link Change [Polling] > <idle>-0 [003] ..s1 182.540350: dwc3_core: Tick! Checking for compliance mode > > <idle>-0 [003] d.s2 182.540362: dwc3_core: Compliance Mode detected. Attempting recovery routine > > irq/23-dwc3-1115 [002] d..1 182.541392: dwc3_event: event (00140301): Link Change [SS.Disabled] > irq/23-dwc3-1115 [002] d..1 182.541976: dwc3_event: event (00150301): Link Change [RX.Detect] > irq/23-dwc3-1115 [002] d..1 182.541982: dwc3_event: event (00170301): Link Change [Polling] > <idle>-0 [003] .Ns1 184.588211: dwc3_core: Tick! Checking for compliance mode > > <idle>-0 [003] dNs2 184.588232: dwc3_core: Compliance Mode detected. Attempting recovery routine Don't we get an interrupt for Compliance mode entry? cheers -- balbi
