Usb Recover

USB Recovery on the HIL Rig

Run this skill's scripts/usb_recover.sh with sudo (abbreviated to usb_recover.sh in the examples below). It wraps the sysfs reset actions, a uhubctl power-cycle escalator, and a resolver:

sudo usb_recover.sh resolve    /dev/ttyACM3    # /dev node -> busport (e.g. 3-4.7); also ttyUSB*, sg*
sudo usb_recover.sh authorized <busport>       # deauthorize+reauthorize: re-enumerate, no VBUS cut
sudo usb_recover.sh rebind     <busport>       # usb driver unbind+bind: re-probe
sudo usb_recover.sh hub-cycle  <busport>       # uhubctl VBUS cycle of the feeding port, walking parent hub
                                               # -> root port until the device re-enumerates
sudo usb_recover.sh pci-rebind <pciaddr>       # whole HCD controller unbind+bind, e.g. 0000:02:00.0
sudo usb_recover.sh pci-reset  <pciaddr>       # PCI function-level reset: kills URBs at HW level, no device lock
sudo usb_recover.sh pci-bind   <pciaddr> [drv] # re-bind a DRIVERLESS controller (auto-tries xHCI drivers)

hub-cycle caveats: leaf hubs that gang (or fake) port power switching bounce all siblings on that hub when cycled; a self-powered leaf hub keeps downstream VBUS up, so cycling it only resets its uplink — that's why the walk escalates to the root port, where the Renesas cards' per-port power (ppps) is real. A device that is wedged but bus-powered from a switching hub gets a true power cycle; one on a self-powered hub may only get a re-enumeration.

Decide first: is anything stuck in D state?

ps -eo pid,stat,wchan:30,cmd | awk '$2 ~ /D/'

If yes (uninterruptible sleep, typically a usbfs ioctl — e.g. testusb inside usb_sg_wait): run pci-reset and NOTHING ELSE first:

sudo usb_recover.sh pci-reset <pciaddr>

FLR kills the URBs at the hardware level without taking the per-device lock; the ioctl then returns and the convoy unwinds on its own.

Not every controller supports FLR. The Renesas uPD720201 (0000:01:00.0) has no reset method — pci-reset fails with Inappropriate ioctl for device (ENOTTY). On those, there is no clean software D-state cure — a VM reboot is NOT reliable (downstream hubs can latch up across the PCIe reset and need a physical replug); ask the operator for a full PVE host power cycle instead. Do NOT fall through to pci-rebind (see next).

pci-rebind can strand the controller driverless. Its unbind succeeds but, with a D-state process still holding a URB, the re-bind hangs — leaving the PCI device with no driver (/sys/bus/pci/devices/<addr>/driver gone) and the whole controller's fixtures offline. A second pci-rebind then dies with "no driver bound". Recover with pci-bind <addr> (re-attaches the xHCI driver); if that also hangs because the D-state URB is unkillable, only a full PVE host power cycle (operator action) recovers. The Renesas binds via xhci-pci-renesas (firmware loader), others via xhci_hcd — pci-bind auto-tries both, or pass the driver explicitly.

Ordering is critical. authorized/rebind/pci-rebind all take the per-device lock the stuck ioctl holds — they block and join the convoy, and soon every libusb tool (uhubctl, JLinkExe) hangs too. Worse, a blocked pci-rebind grabs the PCI device lock on its way in, which pci-reset also needs: once a rebind has been attempted and is stuck, even FLR deadlocks and only a full PVE host power cycle recovers. pci-reset first (if supported), and never pci-rebind a D-state wedge.

If no (device merely dead or silent), escalate gently:

1. authorized <busport> — re-enumerates just that device
2. rebind <busport> — re-probe; also worth trying on the parent hub's busport
3. hub-cycle <busport> — VBUS cycle of the feeding port, walking up to the root port; may bounce sibling fixtures on ganged hubs
4. pci-rebind <pciaddr> — last resort: bounces every fixture on that controller

Finding targets

grep -l <SERIAL> /sys/bus/usb/devices/*/serial          # serial -> busport (dir name)
readlink -f /sys/bus/usb/devices/usb<N>                  # bus N -> its PCI addr in the path

Rig layout (2026-07-15, two Renesas uPD720201 cards; bus numbers renumber every boot — re-derive with readlink): AMD 0000:02:00.0 = the debug-probe tree (J-Links, ST-Links, WCH-Links), no port power switching; Renesas 0000:01:00.0 and 0000:03:00.0 = DUT device hubs + serial fixtures, and ALL their root-hub ports have real per-port power (ppps, 4+4 each) — sudo uhubctl -l <bus> -p <port> -a cycle cuts VBUS to the leaf hub on that port. The 1a40:0201 leaf hubs themselves claim "ganged" switching but do not actually cut power.

Common mistakes

• resolve takes a /dev node, not a busport or serial ("no such device node").
• authorized/rebind take a busport (3-4.7); pci-rebind/pci-reset take a PCI addr.
• Command produces no output and doesn't return → it is blocked on the device lock: a D-state holder exists; see above.
• Trying pci-rebind on a D-state hang — its re-bind hangs and strands the controller driverless; recover with pci-bind <addr>, or a PVE host power cycle if the D-state URB is unkillable. Use pci-reset (if supported) for D-state, never pci-rebind.
• Running pci-reset on a controller without FLR support (Renesas) → ENOTTY; no software recovery — needs a PVE host power cycle.
• A J-Link reset (r; go) does not disconnect a wedged DUT from the host: the DWC2 soft-connect pullup stays up through a core halt, so stuck URBs stay stuck.