On Thu, Jul 2, 2020 at 2:44 PM John Stultz <john.stultz@xxxxxxxxxx> wrote: > > I've been tripping over an issue on my HiKey960 where with the usb-c > gadget cable connected, the gadget code doesn't consistently seem to > initialize properly. I had rarely seen this behavior previously, but > more recently it has become more frequent and annoying. > > Usually, unplugging and replugging the USB-C cable would get things > working again (but that's not helpful in test labs). > > I annotated a bunch of code trying to understand what was going on and > I narrowed down the difference in the good and bad case to a dwc3 > reset interrupts happening after usb_gadget_probe_driver() completes. > In the good case, we see the reset interrupts, and in the failed case > we don't. So I've kept digging around on this, and started dumping registers at the end of dwc3_gadget_start() and then dwc3_gadget_pullup() as that still is called shortly after in both cases. The one consistent difference between the working and not working case I saw was the DWC3_DSTS_COREIDLE bit in the DWC3_DSTS register. It seems when we get to gadget_start()/pullup() if the DSTS_COREIDLE bit isn't on we won't get the reset irq. I added a simple timeout loop to pullup() similar to the DSTS_DEVCTRLHLT loop, but in the failure mode it always times out with COREIDLE not being set. Searching around hasn't provided any info on what COREIDLE actually means, so I'm a bit in the dark. Any clues? thanks -john
