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:

1. 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.
2. Probe. Run modify_pinmux.py probe to parse the XLSM into the per-skill scratch <KB>/pinmap/<custom-carrier>.json plus session.json shim.
3. 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.
4. 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.
5. Generate. `modify_pinmux.py generate –out-dir /Linux_for_Tegra/bootloader/` (root, **not** `bootloader/generic/BCT/` — derive-carrier `.dts` forks live there, do not colocate). Emits: `tegra-mb1-bct-{pinmux,gpio,padvoltage}-.dtsi`. **`` comes from the carrier conf's `PINMUX_CONFIG=` reference, NOT the kebab-cased carrier name.**
6. 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.
7. 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/.
8. 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

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.