Nexus Q Reloaded -- postmarketOS Port

Port of the Google Nexus Q (codename steelhead) to postmarketOS using a mainline Linux 6.12 LTS kernel.

Hardware

Component	Chip	Driver	Bus
SoC	TI OMAP4460 (Cortex-A9 x2)	omap4	-
Audio Codec	TI TWL6040	snd-soc-omap-abe-twl6040	McPDM (I2C1)
Audio Amp	TI TAS5713 25W Class-D	snd-soc-tas571x	McBSP2 (I2C4)
WiFi	Broadcom BCM4330	brcmfmac	SDIO (MMC5)
Bluetooth	Broadcom BCM4330	hci_bcm	UART2
NFC	NXP PN544	pn544_i2c	I2C3
Ethernet	SMSC LAN9500A	smsc95xx	USB EHCI
HDMI	OMAP4 DSS + TPD12S015A	omapdrm	DSS
LEDs	AVR MCU + LP5523	leds-lp5523	I2C2
PMIC	TI TWL6030	twl-core	I2C1

Status

postmarketOS (systemd) boots; the device is daily-usable. SSH over USB gadget and WiFi (BCM4330), HDMI desktop, LED ring + rotary keys, and a full host-built rootfs. Since the 2026-06-10 snapshot below, several "dead" verdicts were overturned:

• Dual-core SMP works (since v1.2.0; re-confirmed nproc=2 on 2026-06-28) — the old "single-core, SMP disabled" status is obsolete.
• CPU frequency scaling 350→1200 MHz (v1.4.0), governor conservative.
• On-board Ethernet (LAN9500A) is NOT dead hardware — fixed in v1.1.0/v1.3.0; currently down again on cpufreq builds (a v1.4.0 boot-timing regression, fix tracked for 1.4.1), not a hardware fault.
• The shipping kernel is built with GCC 15.2 (Alpine, via pmbootstrap) and boots — the historical "GCC 13.3.Rel1 only" constraint applied to an early hand-cross-compiled build, not this path.
• armv7 python3 works on the device (v1.6.0, flash-verified). The long-standing crash (python3 -S -c '' → rc 139 in Py_Initialize, taking down onboard / blueman / sleep-inhibitor / gdb) was a flash bug, not a build bug: raw2simg.py emitted all-zero blocks as DONT_CARE, which the Nexus Q's non-erasing U-Boot left as stale eMMC data, re-corrupting libpython's should-be-zero regions on-device — fixed by writing a byte-exact all-RAW sparse. v1.6.0 ships a plain default-linker (bfd) python3 rebuild that supersedes Alpine's broken -r2, with a build-integrity gate (scripts/verify-libpython-clean.py) + ship gate kept as a safety net. (A qemu-user build-corruption theory and a gold-linker workaround were tried and dropped as unnecessary — 6/6 default-linker builds were gate-clean.) Verified on a fresh flash (no live-patch): libpython3.14.so.1.0 md5 79a0d4ace1358bb2d94c8a4d72479da9, python3 rc 0. See CHANGELOG.md and docs/2026-06-28-session-findings.md.
• Spotify Connect (librespot) ships in the build (librespot 0.8.0, libmdns zeroconf; advertises "Nexus Q", discovery + auth + streaming verified over 5 GHz WiFi). Baked into device-google-steelhead (pkgrel 11) as of v1.6.1 — the systemd unit, the nexusq ALSA PCM (asound.conf) and the nftables drop-in now survive a flash.
• TAS5713 25 W amp works (correct pitch/speed). The v1.6.0 speaker path played exactly 2× too fast (McBSP2 left CLKGDV=0 + a 256-BCLK frame → FSYNC at 2× the rate); fixed in v1.6.1 by kernel patch 0022 (derive CLKGDV from the real fclk + a minimal I2S frame). Verified on hardware: 60 s of audio now plays in 60.00 s (ratio 1.000×; was ~30 s). The old "B7 TAS5713 MCLK 16 vs 12.288" concern was a red herring. See docs/2026-06-29-spotify-connect-and-tas5713-2x-speed.md.

See CHANGELOG.md for the per-milestone record and HANDOFF.md for technical notes and root-cause analysis. See PLAN.md for the hardware status map and the prioritized roadmap (TAS5713 amplifier + Spotify Connect now done; TOSLINK/SPDIF + the ethernet 1.4.1 regression next).

Quick Start

# Build inside Docker
./docker-build.sh

# Or: build boot image manually (requires arm-none-eabi-gcc cross compiler)
# See docker-build.sh for the full build procedure

Project Structure

kernel/
  dts/omap4-steelhead.dts          Device tree source
  configs/steelhead_defconfig      Kernel configuration
  patches/0001-*.patch             TAS5713 driver support
  patches/0002-*.patch             TAS5713 DT binding
  patches/0003-*.patch             Steelhead DTS in kernel tree
pmos/
  device-google-steelhead/         postmarketOS device package
  linux-google-steelhead/          postmarketOS kernel package
  firmware-google-steelhead/       BCM4330 firmware package
build-and-flash.sh                 Automated build and flash script

Flashing

The Nexus Q has hardware-triggered fastboot mode (cover mute LED during power-on). The device is unbrickable as long as the bootloader partition is never overwritten.

Partition Layout

Partition	Size	Usage
boot	8 MB	Kernel + embedded initramfs + DTB (6.7 MB fits)
system	1 GB	Not used (too small for rootfs)
userdata	13 GB	Rootfs target

Flash Commands

# Flash kernel to boot partition (ramdisk-less, must fit the 8 MB boot partition):
fastboot flash boot output/nexusq-boot-v1.6.1.img

# Flash rootfs to userdata partition. The -S 100M chunking is REQUIRED: the 2012
# U-Boot has a ~150 MB download buffer and fails SILENTLY on a larger blob.
# The sparse is all-RAW (byte-exact, since v1.6.0) -- U-Boot never erases userdata, so
# the image must write every block (zeros included), not skip them as DONT_CARE.
fastboot -S 100M flash userdata output/nexusq-rootfs-v1.6.1-sparse.img

# Then power-cycle WITHOUT holding mute sensor to boot normally.

IMPORTANT:

• Always do a full power cycle (unplug power) between flash operations
• Do NOT use fastboot boot (RAM boot) -- it is unreliable on this U-Boot
• NEVER flash the bootloader partition

Testing Pipeline

1. make dtbs_check -- validate device tree
2. pmbootstrap kconfig check -- validate kernel config
3. pmbootstrap build -- cross-compile
4. pmbootstrap qemu -- QEMU boot test (vexpress-a9)
5. fastboot flash boot nexusq-boot-v*.img -- flash kernel (ramdisk-less, <=8 MB)
6. fastboot -S 100M flash userdata nexusq-rootfs-v*-sparse.img -- flash rootfs

Releases

Versioning is tag-only (milestone-based). Images are built locally (the kernel and rootfs aren't built in GitHub CI) and attached to the GitHub release:

• nexusq-boot-vX.Y.Z.img -- kernel + initramfs boot image
• nexusq-rootfs-vX.Y.Z-sparse.img -- postmarketOS rootfs (Android sparse)

End-user flashing is in INSTALL.md; build steps in HANDOFF.md; version history in CHANGELOG.md.

License

GPL-2.0 -- this repository carries Linux kernel patches, a device tree and a defconfig, which are derivative works of the Linux kernel (GPLv2).