On Mon, Dec 20, 2021 at 04:34:13PM +0200, Mathias Nyman wrote: > On 17.12.2021 15.55, Peter Zijlstra wrote: > > On Fri, Dec 17, 2021 at 01:01:43PM +0200, Mathias Nyman wrote: > >> I can reproduce this. > >> Looks like problems started when driver converted to readl_poll_timeout_atomic() in: > >> > >> 796eed4b2342 usb: early: convert to readl_poll_timeout_atomic() > > > > I can confirm, reverting that solves the boot hang, things aren't quite > > working for me though. > > > >> Seems to hang when read_poll_timeout_atomic() calls ktime_* functions. > >> Maybe it's too early for ktime. > > > > It certainly is, using ktime for delay loops sounds daft to me anyhow. > > > >> After reverting that patch it works again for me. > > > > [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.16.0-rc3+ root=UUID=a652986c-fbc6-4341-85c3-b4ad4402f130 ro debug ignore_loglevel sysrq_always_enabled usbcore.autosuspend=-1 earlyprintk=xdbc force_early_printk sched_verbose ftrace=nop mitigations=off nokaslr > > ... > > [ 0.000000] xhci_dbc:early_xdbc_parse_parameter: dbgp_num: 0 > > ... > > [ 3.161367] xhci_dbc:early_xdbc_setup_hardware: failed to setup the connection to host > > Ok, this is some other issue. I got the boot messages over USB > (running minicom at the other end, listening to ttyUSB0) I have a regular A->A USB3 cable, not the special one with a wire missing. Given the dbc thing works, I feel this ought to work too. > > The machine does boot.. but I *am* getting tons of: > > > > [ 485.546898] usb usb4-port4: Cannot enable. Maybe the USB cable is bad? > > [ 485.546963] usb usb4-port4: config error > > This is expected when xhci driver takes over after the early dbc driver, > xhci driver resets xHC controller, and all ports turn to normal host ports again. > > Because of the special cable you now have two hosts connected to each other, > both trying to enumerate a device. > > This whole transition from earlyprintk xdbc to normal xhci driver is > not very userfriendly. Uhhmm... but but that shouldn't be. What if I want to keep using xdbc as console after that point? specifically, I'll probably end up having: earlyprintk=xdbc,keep once all this starts working. The whole point of early consoles is that they're more reliable than regular consoles, not that they're 'early'. > > However, when I do: > > > > $ echo enable > /sys/bus/pci/devices/0000:00:14.0/dbc > > > > Yes, this works as it turns on the DbC feature on in xHC hardware, > which turns the first USB port into a usb device. But if this works, why isn't earlyprintk working for me?
