Hi Lu, I was unfortunate enough to need xdbc and can't get my machine to boot with earlyprintk=xdbc on the cmdline. When I boot the target without the earlyprintk=xdbc, but have the cable attached, it won't boot because boot gets stuck like: Dec 2 15:08:10 tigerlake kernel: [ 42.043137] usb usb4-port3: Cannot enable. Maybe the USB cable is bad? Dec 2 15:08:10 tigerlake kernel: [ 42.043227] usb usb4-port3: config error However, when I boot without earlyprintk=xdbc, without the cable attached, then I can attach the cable and: $ echo enable > /sys/bus/pci/devices/0000:00:14.0/dbc will actually work, and it shows up on my host system: [1023855.419430] usb usb2-port3: Cannot enable. Maybe the USB cable is bad? [1023855.419455] usb usb2-port3: config error [1023859.491476] usb usb2-port3: Cannot enable. Maybe the USB cable is bad? [1023859.491487] usb usb2-port3: config error [1023861.335436] usb usb2-port3: config error [1023861.607476] usb 2-3: new SuperSpeed USB device number 7 using xhci_hcd [1023861.627614] usb 2-3: LPM exit latency is zeroed, disabling LPM. [1023861.627853] usb 2-3: New USB device found, idVendor=1d6b, idProduct=0010, bcdDevice= 0.10 [1023861.627855] usb 2-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [1023861.627856] usb 2-3: Product: Linux USB Debug Target [1023861.627857] usb 2-3: Manufacturer: Linux Foundation [1023861.627858] usb 2-3: SerialNumber: 0001 [1023861.629344] usb_debug 2-3:1.0: xhci_dbc converter detected [1023861.629532] usb 2-3: xhci_dbc converter now attached to ttyUSB0 Can you please see if you can repro and fix this? This all was with current 5.16-rc3 on a tigerlake nuc. Also, perhaps you can update the guide on what sort of setup/cables etc.. you need when either the host or the client is a usb3.1 usb-c only device.
