Hello Felipe, On Thu, Jul 11, 2019 at 10:37:11AM +0300, Felipe Balbi wrote: > Rob Weber <rob@xxxxxxxxxxx> writes: > > 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. Okay, understood. > > > 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. Okay, good to know. I am not confident in this approach as well because of the state management / recovery we might have to perform. I wanted to explain our goal a little bit more in depth in case some other apprach might come to mind. Our product supports 3 ways in which the user can work with the USB port: Host mode, Mass Storage Mode, and Ethernet Mode. Host mode is pretty straightforward. Users will generally work with USB mass storage devices and USB-Ethernet adapters in host mode. Mass storage mode exposes an internal user data partition using f_mass_storage and configfs so the user can connect our product to their host computer for backing up data. Ethernet uses the f_ecm and f_rndis functions creating an ethernet connection with USB hosts, particularly mobile devices, to interact with our mobile applications and servers through a wired connection. We control this functionality through a userspace application written in Go that creates the gadget/function configuration in configfs. Given this background information, are there any approaches that come to mind, such as reconfiguring the gadget? Thanks in advance for your input. > > 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 Great, thank you. I will give these a shot and let you know if I have further questions. > > /* -------------------------------------------------------------------------- */ > > # 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? Not that I've seen, surprisingly. My compliance mode recovery mechanism looks for both compliance mode and loopback mode, neither of which I have ever seen in the link state change events. Cheers, Rob Weber
