Jetson Customize Usb Agent Skill

Customize USB (per-port enable / disable / role)

Purpose

Enable, disable, or change the role of USB2 / USB3 SS ports on a

Jetson Thor (Tegra264) or Orin (Tegra234) custom carrier. Captures

per-port wiring (role, max speed, VBUS-EN / OC GPIOs, CC1/CC2 GPIOs

for Type-C, USB3 SS UPHY lane), resolves the SS to USB2 companion

graph from the in-tree DTB, then renders a self-contained kernel-DT

overlay that flips every port action in three places in lockstep

(lane status, port status, host xHCI phys + phy-names).

UPHY lane allocation belongs to jetson-customize-uphy. No ODMDATA

edit. Output is one commit to the composite custom overlay .dts in

the bsp_sources/ hardware repo.

Prerequisites

• Active profile with reference_devkit: + custom_carrier: blocks.
• <source.root_path>/Linux_for_Tegra/.git exists

(/jetson-init-source).

• /jetson-derive-carrier has run — carrier flash-conf fork in the

overlay tracker.

• /jetson-customize-uphy has run when any enabled USB3 SS port

needs a non-stock UPHY lane allocation. Its JSON sidecar at

<workspace>/target-platform/<profile-stem>.jetson-customize-uphy.json

is consulted for SS lane allocation.

• Source-of-truth docs: Adaptation Guide §"Port the Universal Serial

Bus", Module Design Guide §USB, SoC TRM (xusb block).

• **When custom_carrier: is present, both

documents.custom_carrier_schematic AND

documents.custom_carrier_pinmux_xls are REQUIRED.** Refuse the run

if either is missing — per-port routing (VBUS-EN / OC / CC GPIOs, SS

lane wiring, hub fan-out) on a custom carrier cannot be guessed.

Reference-devkit-only profiles skip this check.

• dtc, fdtoverlay on PATH.

Overview

USB on Tegra spans three IP surfaces: the xusb_padctl block (USB2

OTG + USB3 SS PHYs), the tegra-xusb xHCI host controller, and an

optional tegra-xudc device controller attached to the single

OTG-capable USB2 port (usb2-0).

A per-port flip MUST touch three kernel-DT places in lockstep.

Anything less crashes the host xHCI probe and leaves lsusb empty

on every port (collateral damage to stock-okay ports):

| # | Place | Path | What it controls |

|---|---|---|---|

| 1 | Lane (PHY provider) | xusb_padctl/pads/usb<2\|3>/lanes/usb<2\|3>-N | SS / OTG PHY hardware-binding. status="disabled" then lane stops providing a PHY. |

| 2 | Port (controller-binding) | xusb_padctl/ports/usb<2\|3>-N | Per-port mode (host/device/otg), companion link, VBUS / OC / CC pin refs. status="disabled" then port removed from user-facing topology. |

| 3 | Host xHCI phys-list | bus@0/usb@<addr>.phys + .phy-names | Array of phandles + names the xHCI driver iterates. A ref to a disabled PHY returns -ENODEV and aborts the whole host probe. |

NVIDIA's stock-disabled usb3-3 in the Thor base DTB is the canonical

pattern — all three places flipped in lockstep.

Two extra rules ride on top of the three-place pattern:

• Rule A — lane + port pairing. Lane (place 1) and matching port

(place 2) MUST flip together.

• Rule B — companion cascade.

xusb_padctl/ports/usb3-N.nvidia,usb2-companion references a USB2

port phandle. Disabling that USB2 without cascading to its SS

companion then tegra-xusb: failed to enable PHYs: -19.

Agentic, not table-driven — every port, controller, lane,

companion link, phandle, and __symbols__ lookup is resolved at

runtime from docs + DTB + carrier pinmap + schematic.

When to invoke

• The user says "enable USB", "disable USB hub", "configure USB3 SS",

"set USB role", "wire VBUS-EN", "tegra-xusb / xudc / dr_mode", or

asks to bring up / take down a USB controller on a custom carrier.

• A USB receptacle on the carrier doesn't enumerate after flash, OR

collateral USB damage (lsusb empty after a previous

jetson-customize-usb attempt) needs to be fixed.

• jetson-customize-uphy re-allocated UPHY lanes affecting USB3 SS

ports and per-port DT now needs to follow.

Procedure (summary)

The full step-by-step procedure lives in references/procedure.md.

• Step 1 — resolve active target + open source-of-truth docs.
• Step 2 — build the USB topology + companion graph from the

in-tree DTB.

• Step 3 — AskUserQuestion for port(s) to enable / disable;

surface companion cascade + on-carrier hub fan-out explicitly.

• Step 4 — per-port verify (module + carrier + UPHY lane) and

capture wiring (VBUS-EN / OC / CC GPIOs via pin_verifier.py).

• Step 5 — render the kernel-DT overlay using the three-place

pattern, append fragments (usb:padctl, usb:xhci, optional

usb:xudc) to the composite custom overlay .dts, run

fdtoverlay + the three post-merge invariants, commit to

bsp_sources/.

• Step 6 — write run-state JSON sidecar (shape in

references/run-state-sidecar.md), emit headline, then drive the

downstream next-step chain via sequential AskUserQuestion prompts

per references/procedure.md Step 6. Never substitute a printed

"Next step: …" line for the prompts.

See references/gotchas.md for the load-bearing failure modes.

Limitations

• Owns kernel-DT overlay only. ODMDATA does not expose a per-port

USB status knob; do not edit it.

• Does NOT allocate UPHY lanes — jetson-customize-uphy owns that.

Refuse to commit an SS-enable until uphy run-state shows the lane

allocated.

• Does NOT directly patch the pinmux DTSI — routes SFIO mismatches

to /jetson-customize-pinmux set-pin.

• Does NOT compile the .dtbo or register OVERLAY_DTB_FILE+= —

/jetson-build-source owns build + flash-conf registration.

• Tegra platform invariant: only usb2-0 is OTG-capable; xudc

attaches there only. All other USB2 ports and all USB3 SS ports

are host-only.

Troubleshooting

• Empty lsusb on every port, USB-eth at 192.168.55.1 still up:

host xHCI bailed; three-place lockstep was broken. Inspect merged

DTB; verify post-merge invariants in references/procedure.md

Step 5d.

• tegra-xusb: failed to enable PHYs: -19: companion cascade

(Rule B) violated — a USB2 was disabled without its SS companion.

• no port found or Requested PHY is disabled: Rule A

violated — lane status and port status are mismatched.

• FDT_ERR_NOTFOUND from fdtoverlay: a fragment used

target = <&label> for a node whose label is not in

__symbols__ (typical for host xHCI / tegra-xudc). Switch to

target-path = "/bus@0/usb@<addr>".

• dtc warning phys_property: cell 0 is not a phandle reference:

benign; expected when using raw integer phandles in the host phys

override.

• Port boots but VBUS never asserts: vbus-supply references a

regulator parent node that does not exist. Ensure the fixed

regulator node is present before referencing it.

• xHCI binds the wrong port at boot: host phys element order

was not preserved. Only elide disabled entries; never reorder

kept ones.

References

• references/procedure.md — full step-by-step procedure.
• references/gotchas.md — load-bearing failure modes.
• references/run-state-sidecar.md — run-state JSON shape.
• references/usb-architecture.md — Tegra USB IP architecture

notes (xusb_padctl, tegra-xusb, xudc).

• references/usb-dt-bindings.md — USB DT binding cheatsheet

(lane / port / phys-list shapes).

• ../../scripts/pin_verifier.py — shared HSIO pin verifier.
• ../../references/platform_template.yaml — documents: block

consumed by Step 1.

• ../../context/bsp-customization-workflow.md — overlay edit

protocol.

• ../../references/bsp-customization-kernel-dtb.md — composite

overlay append protocol.

• ../jetson-customize-uphy/SKILL.md — sibling skill that owns

UPHY lane allocation.

• ../jetson-customize-pinmux/SKILL.md — sibling skill for

VBUS-EN / OC / CC SFIO fixes.

• ../jetson-derive-carrier/SKILL.md — must run first.
• ../jetson-init-source/SKILL.md — produces the overlay tracker

+ bsp_sources repo.