Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes: > On Tue, Jan 25, 2022 at 02:09:18PM +0100, Sven Schnelle wrote: >> Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes: >> >> > Now the documentation states we need this super speed A<->A cable, but >> > could you also update the documentation for usb-c ? There's a fair >> > number of usb-c only devices out there now. >> >> Stupid beginners question: Would every USB3 A-A cable work, or are the >> debug cables special? I've read the RX/TX pairs have to be swapped, but >> to me it looks like that's always the case? > > I'm using a random USB3 A-A cable (it came with an HDMI frame grabber of > of AliExpress). The official one has a wire missing I think, to avoid > ground loops or something like that. > > The easiest thing to do is try the runtime DBC option: > > echo enable > /sys/bus/pci/devices/0000:00:14.0/dbc > > If that works you can see what it takes to make the earlyprintk one > working. This thread seems to have much of that covered. Thanks, the sysfs test works for me. I have two A-A cables, one is from a cheap PCI-e extender, the other one from a KVM switch. Both work, which is great. So i assume that most A-A cable would work. I'm building a new kernel now with the patch on top, lets see. Thanks!
