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

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):

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.

1. Step 1 — resolve active target + open source-of-truth docs.
2. Step 2 — build the USB topology + companion graph from the in-tree DTB.
3. Step 3 — AskUserQuestion for port(s) to enable / disable; surface companion cascade + on-carrier hub fan-out explicitly.
4. Step 4 — per-port verify (module + carrier + UPHY lane) and capture wiring (VBUS-EN / OC / CC GPIOs via pin_verifier.py).
5. 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/.
6. 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.