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SpacemiT K3 (RISC-V) — Android device support

This directory is the AOSP device config for the SpacemiT K3 SoC (spacemit,x100; 8× out-of-order RVA23 cores, RVV/RVH, A100 NPU, PowerVR BXM-4-64 GPU, riscv64). It targets the Muse Pico-ITX board.

The K3 shares one common kernel with the K1 (see "Kernel" below): a single GKI-style Image + per-board DTBs + a union module set. SoC drivers bind by device-tree compatible, so K1 and K3 coexist in the same tree with no regression to either.

Board SoC compatible Bootloader media Android media
Muse Pico-ITX K3 / x100 spacemit,k3-pico-itx, spacemit,k3 SPI-NOR UFS 2.2

The board boots its bootloader from SPI-NOR, then Android from UFS (UFS 2.2, 128/256 GB — there is no eMMC). The UFS user LU carries the GPT; the bootloader lives on the NOR. See "Storage" below.

One device, one product

The device is k3; the lunch product lives in k3_pico_itx/:

  • aosp_k3_pico_itx — lunch aosp_k3_pico_itx-trunk_staging-userdebug

device/spacemit/k3/device.mk inherits device/spacemit/common (SoC-agnostic HALs, the Mesa GPU stack, A/B, codecs, webview, …) and adds the K3-specific fstab, init, firmware, and storage/WiFi/BT wiring.

Kernel: one common K1 + K3 build

Both SoCs build from the same kleaf target spacemit_k1x in devices/spacemit/spacemit_soc/ (this directory was historically named bananapi_f3/; it was renamed because it is no longer K1/BPI-F3-specific — it is the common SpacemiT SoC kernel). DTBs emitted from common/arch/riscv/boot/dts/spacemit/:

  • k1-bananapi-f3.dtb, k1-musepi-pro.dtb (K1 boards)
  • k3-pico-itx.dtb (this board)

Build / re-stage the kernel prebuilt:

cd <kernel>
./tools/bazel run --config=spacemit_k1x \
    //devices/spacemit/spacemit_soc:spacemit_k1x_dist -- \
    --destdir=<aosp>/device/spacemit/kernel/<version>

<version> is the directory TARGET_KERNEL_USE names — mainline (default) or 6.18, the latter built from the kernel-6.18/ tree. K1 and K3 share one kernel, so there is one drop zone per version and none per SoC.

The config fragment is devices/spacemit/spacemit_soc/spacemit_k1x.fragment (K3 options are gated/added there; K1 options are untouched).

Functional bring-up status

All peripherals below are ported, build-GREEN, and folded into the flashable image set. Hardware validation (probe, scan-out, link-training, enumeration) is pending the real board.

Function Kernel Firmware Notes
Display spacemit-drm-k3.ko (DPU saturn) + spacemit_inno_dp.ko (DP/eDP) — eDP 40-pin (2.5K) + USB-C DP (4K, DP-Alt-Mode). K3-gated, separate from K1 spacemit-drm.ko.
GPU upstream open-source drm/imagination (DRM_POWERVR); BVNC 36.56.104.183 (BXM-4-64) powervr/rogue_36.56.104.183_v1.fw userspace = Mesa (≥26.1) powervr_dri.so. Firmware from the Imagination linux-firmware repo.
USB dwc3 + phy-k3-usb2/phy-k3-usb3 + fusb301 (Type-C) — USB2 host + USB3 portA(DRD)/portD + FUSB301 TCPC (irq gpio 2/21).
WiFi rtw89_8852be (RTL8852BE, PCIe) rtw89/rtw8852b_fw.bin M.2 module; PCIe brought up (K3 PCIe PHY + RC).
Bluetooth btusb + btrtl (RTL8852B, USB) rtl_bt/rtl8852bu_* standard Android BT HAL (USB HCI, no UART transport).
Storage (UFS) ufs-spacemit.ko (spacemit,k3-ufshcd) — boot device; loaded from the vendor_boot ramdisk.
Audio (DP) snd-soc-k3-ri2s + adma-spacemit (RCPU domain) → DP codec — DP-audio over the DisplayPort (Linux-direct, no RT-coprocessor firmware).

Known gaps (need the board, or further work):

  • Analog audio (ES8326) sits on a secure I²C bus (i2c3@f0614000, APBC2) not exposed to Linux in this tree → the analog headphone codec is not wired; DP-audio is the available path.
  • All of the above is compile/integration-level; runtime validation requires the hardware (PCIe link-up, UFS enumeration, DP link-training, etc.).

Storage (UFS, not eMMC)

androidboot.boot_devices points at the UFS host (soc/c0e00000.ufshc); the fstab uses bus-agnostic /dev/block/by-name/* (resolved off the GPT PARTLABEL on the UFS user LU). ufs-spacemit.ko is force-loaded early via BOARD_VENDOR_RAMDISK_KERNEL_MODULES_LOAD so UFS probes before first-stage mount. The bootloader (U-Boot 2026.07) already has UFS + the K3 controller.

Bootloader staging

Built from upstream U-Boot 2026.07 + OpenSBI (K3 port) through the same build-bootloaders env as the K1 — release_android.sh driven by config/boards/spacemit-k3.yaml — and staged to vendor/spacemit/k3/bootloader/ (u-boot-release.itb, fw_dynamic, env, factory/{FSBL,bootinfo_*}). release_android.sh itself is unmodified; the K3 is a new yaml + minimal, default-preserving generalization of the shared shell helpers (the K1 build is byte-for-byte unchanged).

Flashing

Use flash_pico_itx.sh (staged to PRODUCT_OUT). The board enters flashing mode via the FDL button; flashing is over the DRD Type-C port with the official Titan tool or fastboot. Bootloader → SPI-NOR, Android → UFS.

./flash_pico_itx.sh --android-media=ufs      # Android to UFS (default for this board)
./flash_pico_itx.sh --help                   # all modes

The flash flow (GPT to UFS, U-Boot fastboot SCSI backend) is self-flagged UNVALIDATED in the script — it needs board validation.

See also

  • flash_pico_itx.sh — the flash tool.
  • device/spacemit/k1/README.md — the K1 boards (BPI-F3, MusePi Pro) that share this kernel.
  • README.fr.md — French version of this document.