Scott Scoble 5051dfdc8c Add T490 hardware configuration and docs

- modules/t490.nix: TLP power management, CPU throttling (throttled), S3 sleep,
  remote Nix builders (cluster), fwupd, fprintd, fprintd, Syncthing, Tailscale,
  Intel VA-API, TrackPoint sensitivity, PipeWire defaults
- flake.nix: add nixos-hardware input, import T490 module + nixos-hardware
- docs/T490-HARDWARE.md: WiFi variants, graphics, audio, fingerprint, sleep guide
- docs/T490-BATTERY.md: TLP config, threshold strategy, real-world battery numbers
- docs/T490-OFFLOADING.md: local vs cluster split, remote builder setup
- MIGRATION.md: add T490 post-install steps (fwupd, fprint, remote build key)
- README.md: reflect new module and docs structure

2026-05-14 17:40:04 -07:00

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T490 Hardware Compatibility

WiFi

Two possible cards depending on SKU:

Intel Wireless-AC 9560 (CNVio, older) — firmware: iwlwifi-9000-pu-b0-jf-b0-*.ucode
Intel Wi-Fi 6 AX200 (M.2, discrete, newer) — firmware: iwlwifi-cc-a0-*.ucode

Both use iwlwifi and work out of the box. If AX200 scan fails after suspend, firmware version may be the culprit. The modules/t490.nix includes a resume hook that reloads the module.

Graphics — Intel UHD 620 (Whiskey Lake)

Single iGPU. No NVIDIA. No Optimus. Ideal for Linux.

Feature	Support
OpenGL 4.6	Mesa Iris driver
Vulkan 1.3	Mesa ANV driver
VA-API decode	H.264, H.265 8-bit, VP9 8+10-bit, MPEG-2, VC-1, VP8
VA-API encode	H.264 only (no H.265)
DisplayPort over USB-C	Up to 4096×2304 @ 60Hz
HDMI 1.4b	Up to 4096×2304 @ 24Hz

Thunderbolt 3

One full-speed TB3 port (also USB-C PD). services.hardware.bolt.enable = true in modules/t490.nix. Lenovo TB3 Dock Gen 2 works — update dock firmware via fwupd.

Fingerprint Reader — Synaptics 06cb:00bd

Works after firmware update. Steps:

fwupdmgr refresh && fwupdmgr update — flashes Prometheus firmware
fprintd-enroll — enroll fingerprints
Works for sudo, login, and screen unlock via PAM

Check: lsusb | grep 06cb should show 06cb:00bd.

Audio

Single Intel audio card (8086:9dc8) with 5 sub-devices (speaker + 4 HDMI/USB-C). The nixos-hardware T490 module provides a custom PulseAudio profile set that exposes all 5 sinks simultaneously.

Sleep / Resume — Critical

The T490 supports S3 (deep sleep) and S0ix (s2idle, modern standby). Lenovo removed S3 from some BIOS versions.

Check:

cat /sys/power/mem_sleep

Output	Status	Action
`s2idle [deep]`	S3 default	Good
`[s2idle] deep`	S3 exists but not default	Already fixed in `modules/t490.nix` (`mem_sleep_default=deep`)
`[s2idle]`	S3 missing	Troubleshoot below

If S3 is missing:

BIOS → Config → Power → Sleep State → "Linux" (re-enables S3 on some versions)
Downgrade BIOS (pre-2020 versions have S3)
Use hibernation instead (more reliable than s2idle)

Sleep battery drain:

S3 (deep): ~0.5%/hour (~8 days on a 50 Wh battery)
s2idle: ~2-4%/hour (1-2 days)

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