Jetson Customize Pinmux Agent Skill

Customize pinmux (per-pin SFIO / direction / state)

Overview

The Tegra pinmux spreadsheet (.xlsm) is the ground truth for every

CVM ball: SoC pin name, supported SFIOs, customer-selected function,

direction, and initial state. This skill parses that XLSM, runs a

per-pin Q1–Q6 interactive loop, and emits the three BCT DTSIs

(pinmux, gpio, padvoltage) in one shot into the overlay tracker

at <source.root_path>/Linux_for_Tegra/bootloader/.

Unlike sibling skills jetson-customize-uphy / jetson-customize-pcie /

jetson-customize-camera, **pinmux has no kernel-DT overlay surface and no

ODMDATA edit**. The XLSM is the source of truth; the three emitted

DTSIs land at flash time via the carrier conf's

PINMUX_CONFIG= / GPIOINT_CONFIG= / PMC_CONFIG= references (which

/jetson-derive-carrier set up).

Pad classification (silicon-fixed): only BD* and BI* pads have

configurable pull / drive / open-drain attributes. LP5XA_*,

UPHYDS_*, DP_SINGLE_*, BDMIPI16X_*, BDUSB2_*, OSCI27_* are

fixed-function and skip Q4–Q6 (configurable: no).

The bundled scripts/modify_pinmux.py is the workhorse: it parses

the XLSM via openpyxl>=3.1, builds the per-carrier pinmap JSON,

captures pin edits into a session shim, and (on generate) writes

the three DTSIs.

When to invoke

• The user says "configure pin", "set SFIO", "edit pinmux DTSI",

"set pin direction", "set initial state", or asks to repurpose a

CVM ball (e.g. flip a pin between GPIO and a peripheral function).

• A sibling skill (jetson-customize-camera, jetson-customize-pcie,

jetson-customize-usb, jetson-customize-mgbe) reports an HSIO pin mismatch

via pin_verifier.py and the user wants to fix it.

• The user pre-derived a custom carrier with /jetson-derive-carrier

and now wants to author the pinmux from a freshly-edited .xlsm.

Prerequisites:

• Active profile selected (target-platform/active_target.yml →

<profile>.yaml with reference_devkit: AND custom_carrier:).

• <source.root_path>/Linux_for_Tegra/ exists as a git repo

(/jetson-init-source).

• /jetson-derive-carrier has run — the three pinmux-side BCT DTSIs

(PINMUX_CONFIG, GPIOINT_CONFIG, PMC_CONFIG references in the

carrier conf) exist in the overlay tracker.

• A pinmux .xlsm is registered in the active profile at

documents.custom_carrier_pinmux_xls (preferred when custom-carrier-

specific) or documents.ref_devkit_pinmux_xls (fallback). The

bundled modify_pinmux.py requires openpyxl>=3.1.

Procedure

See references/procedure.md for the full

step-by-step procedure (Steps 1–8). Summary:

• Resolve active target + XLSM. Validate active profile,

custom_carrier:, overlay-tracker prerequisites; resolve the

pinmux .xlsm path from

documents.custom_carrier_pinmux_xls →

documents.ref_devkit_pinmux_xls → single XLSM under

documents.root_path → user prompt.

• Probe. Run modify_pinmux.py probe to parse the XLSM into the

per-skill scratch <KB>/pinmap/<custom-carrier>.json plus

session.json shim.

• Lookup. Resolve a free-form user query (CVM ball, Verilog

name, signal, DT pin) via modify_pinmux.py lookup; surface

supported SFIO list, defaults, and configurable: yes/no.

• Set-pin (HARD GATE — Q1–Q6 via AskUserQuestion). Q1–Q3

(sfio / direction / initial_state) always asked; Q4–Q6

(pull / drive_type / open_drain) only when

configurable: yes. tristate and e_input are derived from

direction, never asked.

• Generate. `modify_pinmux.py generate --out-dir

<source.root_path>/Linux_for_Tegra/bootloader/` (root, not

bootloader/generic/BCT/ — derive-carrier .dts forks live there,

do not colocate). Emits:

tegra<soc>-mb1-bct-{pinmux,gpio,padvoltage}-<carrier-key>.dtsi.

**<carrier-key> comes from the carrier conf's PINMUX_CONFIG=

reference, NOT the kebab-cased carrier name.**

• Commit (single batched commit per workflow rule). All three

DTSIs are one logical edit → one customization commit. Run the

commit-preview gate before each commit.

• Run-state sidecar + session shim. Write the user-facing

<profile-stem>.jetson-customize-pinmux.json sidecar and the

transient session.json shim under

<workspace>/target-platform/.

• Summary. Emit the standard one-line + table summary.

Gotchas

• **No kernel-DT overlay; no OVERLAY_DTB_FILE edit; no

render_conf.py hand-off.** This skill ends at the three BCT

DTSIs — the carrier conf already references them via

PINMUX_CONFIG= / GPIOINT_CONFIG= / PMC_CONFIG= (set up by

/jetson-derive-carrier).

• Re-point the .dts wrapper's #include after generate.

/jetson-derive-carrier forks the .dts wrappers at

bootloader/generic/BCT/, but their #include lines may still

pull the upstream devkit .dtsi (e.g.

…-p3834-xxxx-p4071-0000.dtsi). After generate writes the new

<CARRIER_KEY>.dtsi to bootloader/ root, edit each wrapper's

#include to the new filename — by bare basename

(#include "tegra<soc>-mb1-bct-pinmux-<CARRIER_KEY>.dtsi"), not

../../… filesystem-relative. The BCT build's cpp -I bootloader/

resolves bare basenames; that's the convention every other BCT

include in the tree follows. Roll the wrapper edits into the same

customization commit as the three DTSIs. See references/procedure.md

Step 5 ("Sanity-check the carrier .dts wrapper").

• Q4–Q6 gated on configurable: yes. Asking pull / drive_type /

open_drain on a fixed-function pad (LP5XA_*, UPHYDS_*,

BDMIPI16X_*, etc.) is silently dropped by the script and confuses

the user. lookup prints configurable: yes/no — always check it

before prompting Q4–Q6.

• tristate and e_input are derived, never asked. unused →

tristate=ENABLE; input / bidirectional → enable-input=ENABLE.

Exposing them as separate prompts produces inconsistent DTSIs.

• **sfio=gpio requires a parseable gpio=GPIOn_PD.NN entry in the

pinmap row's sfio list.** Pins without one are GPIO-incapable

silicon; set-pin rejects the call. Surface the rejection — don't

silently fall back to a non-GPIO SFIO.

• Marker idempotency. Every per-pin edit carries

// custom-bsp: pinmux on the closing brace; gpio default-state

entries carry the same marker as a trailing comment. Re-running

generate must detect and update — never duplicate.

• modify_pinmux.py is unchanged from the original framework —

it reads its own session.json shim under --kb-dir. The shim

is regenerated each run from the active profile + the user-facing

sidecar. Do not hand-edit the shim; it's transient.

• Multiple pinmux DTSI variants per Thor module SKU. Some carrier

pins live in a different DTSI variant than the one the carrier

conf references. modify_pinmux.py commit (legacy patch-in-place

flow) tolerates missing per-pin blocks via

pinmux.warnings[] rather than failing. Surface the warning;

point at the alternate DTSI variant.

• Don't touch the upstream BSP at <bsp_image.root_path>. All

edits land in <source.root_path>/Linux_for_Tegra/bootloader/ under

the pristine + customization commit pattern.

Available Scripts

| Script | Purpose | Arguments |

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

| scripts/modify_pinmux.py | XLSM parser + per-pin DTSI generator. Invoked via run_script() from Steps 3-6 with the subcommand of the current phase. | probe \| lookup \| set-pin \| apply \| generate \| commit [...] (see --help) |

| scripts/generate_dtsi.py | Renders pinmux/GPIO/padvoltage DTSI fragments from the bundled session state. Called by modify_pinmux.py generate. | --session <path> --out-dir <dir> |

Invoke from the skill body as a subprocess via run_script():

# run_script: probe the carrier pinmux XLSM and write a session state
scripts/modify_pinmux.py probe --xlsm carrier.xlsm --session .pinmux-session.json

# run_script: render DTSI fragments from the final session state
scripts/modify_pinmux.py generate --session .pinmux-session.json --out-dir bsp_sources/pinmux/

References

• references/procedure.md — full Step 1–8

procedure prose.

• questions.json — Q1–Q6 prompt schema consumed

by Step 4.

• ../../references/platform_template.yaml — documents: block (ref_devkit_pinmux_xls, custom_carrier_pinmux_xls).
• ../../context/bsp-customization-workflow.md — overlay edit protocol (single-commit per DTSI fork).
• ../jetson-derive-carrier/SKILL.md — must run first; produces the pinmux / gpio / padvoltage DTSI forks this skill edits, and rewrites the carrier conf's PINMUX_CONFIG= / GPIOINT_CONFIG= / PMC_CONFIG= lines to point at them.
• ../jetson-init-source/SKILL.md — produces the overlay tracker this skill commits into.
• ../jetson-link-docs/SKILL.md — author the profile's documents: block, including the pinmux XLSM bindings.