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Board Support Request: Walnut Pi Zero W (Allwinner H618) #9749

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Board Support Request: Walnut Pi Zero W (Allwinner H618)#9749
@davkdavk

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@davkdavk
davkdavk
opened on May 3, 2026

Armbian Board Support Request: Walnut Pi Zero W

1. Board Overview

Hardware Specifications

  • SoC: Allwinner H618 (sun50iw9) — Quad-core Cortex-A53 @ 1.5GHz, 1MB L2 cache
  • Architecture: ARM64 (aarch64)
  • GPU: Mali G31 MP2 (Bifrost architecture)
    • Supports OpenGL ES 1.0/2.0/3.2, OpenCL 2.0
  • RAM Options:
    • 1GB (2x 512MB DDR3)
    • 2GB (LPDDR4)
    • 4GB (LPDDR4)
  • Storage: MicroSD slot (supports up to 512GB), Reserved SPI Flash (unpopulated)
  • Video Output: MicroHDMI 2.0a, supports 4K@60fps
  • Wireless: Dual-band WiFi (2.4G & 5G) + Bluetooth 5.0
    • Chip: UWE5622 (SDIO)
    • Kernel modules: sprdwl_ng, sprdbt_tty
  • Ethernet: 100Mbps via AC200 EPHY (internal PHY)
  • USB: 1x USB-C (OTG), 2x USB 2.0 via FPC expansion connector
  • Audio: 3.5mm audio jack (via expansion board)
  • GPIO: 40-pin header (Raspberry Pi compatible)
  • FPC Connector: 24-pin (exposes USB 2.0 x2, Ethernet, audio, IR receiver, UART, power output 5V/3.3V)
  • Dimensions: 65 x 30 x 5 mm (PCB size)
  • Weight: 8.5g (bare board)
  • Power: Type-C 5V/1A input

Similarities to Orange Pi Zero 2W

  • Same SoC: Allwinner H618 (sun50iw9)
  • Same PMIC: AXP313A (I2C address 0x36)
  • Same WiFi/BT: UWE5622 (sprdwl_ng, sprdbt_tty)
  • Same Ethernet: AC200 EPHY (100Mbps)
  • Same GPU: Mali G31 MP2

Key Differences from Orange Pi Zero 2W

Feature Walnut Pi Zero W Orange Pi Zero 2W
Form Factor 65x30mm (Zero W) 55x30mm
RAM Options 1GB/2GB/4GB 1GB/1.5GB/2GB/4GB
SPI Flash Reserved (unpopulated) 16MB populated
USB-C 1x (OTG only) 2x (UFP + DFP)
Expansion FPC connector FPC connector
Vendor Kernel 6.1.31 (walnutpi/linux) 6.1.y (orangepi/linux)
Vendor U-Boot walnutpi/u-boot orangepi/u-boot

2. U-Boot

Vendor U-Boot Source

Mainline U-Boot Support

  • Status: Full H616/H618 support merged in mainline U-Boot
  • Defconfig: orangepi_zero3_defconfig (works for H618 boards)
  • Device Tree: sun50i-h618-orangepi-zero3.dts (can be adapted)
  • Key Config Options: 
    CONFIG_MACH_SUN50I_H616=y
CONFIG_SUNXI_DRAM_H616_LPDDR4=y
CONFIG_AXP313_POWER=y
CONFIG_SUN8I_EMAC=y
CONFIG_PHY_MOTORCOMM=y  # For Ethernet
  • DRAM Parameters (from Orange Pi Zero 3 defconfig): 
    CONFIG_DRAM_SUN50I_H616_DX_ODT=0x07070707
CONFIG_DRAM_SUN50I_H616_DX_DRI=0x0e0e0e0e
CONFIG_DRAM_SUN50I_H616_CA_DRI=0x0e0e
CONFIG_DRAM_SUN50I_H616_ODT_EN=0xaaaaeeee
CONFIG_DRAM_SUN50I_H616_TPR6=0x44000000
CONFIG_DRAM_SUN50I_H616_TPR10=0x402f6663
CONFIG_DRAM_SUN50I_H616_TPR11=0x24242624
CONFIG_DRAM_SUN50I_H616_TPR12=0x0f0f100f
CONFIG_DRAM_CLK=792

Important U-Boot Patches for H618

  1. GPU Power Domain Enable (Critical for Panfrost):

  2. THS Temperature Sensor Workaround:

Recommended U-Boot Approach for Armbian

  1. Option A (Recommended): Use mainline U-Boot with patches

    • Base: tag:v2024.01 or later
    • Apply GPU enable hack patch
    • Create new defconfig: walnutpi_zerow_defconfig
    • Adapt DTS from sun50i-h618-orangepi-zero3.dts

  2. Option B: Fork walnutpi/u-boot

    • More work to maintain
    • Ensures vendor-specific features work (HDMI, WiFi)
    • Would need to rebase on mainline periodically

3. Kernel

Vendor Kernel Source

  • Repository: https://github.com/walnutpi/linux
  • Branch: orange-pi-6.1-sun50iw9 (BSP kernel)
  • Version: 6.1.31
  • Features:
    • Proprietary Mali driver (mali.ko)
    • HDMI output working
    • WiFi/BT working (UWE5622)
    • Ethernet via AC200 PHY
    • Audio (via expansion board)

Mainline Kernel Support

Sunxi64 Family Configuration

The H618 belongs to the sunxi64 family in Armbian:

  • Family Config: config/sources/families/include/sunxi64_common.inc
  • LINUXFAMILY: sunxi64 (for next/edge branches)
  • ATF (ARM Trusted Firmware):

Kernel Configuration for Armbian

Based on Orange Pi Zero 2W (sun50iw9 family):

LINUXFAMILY="sun50iw9"  # Or "sunxi64" for mainline

# For current branch (6.12.y):
KERNELSOURCE='https://github.com/torvalds/linux'
KERNELBRANCH='branch:linux-6.12.y'
KERNELPATCHDIR='archive/sunxi-6.12'

# For edge branch (6.15.y):
KERNELSOURCE='https://github.com/torvalds/linux'
KERNELBRANCH='branch:linux-6.15.y'
KERNELPATCHDIR='archive/sunxi-6.13'  # Or sunxi-6.15 when available

4. GPU/Panfrost — Fully Documented

Root Cause of GPU Failure (Discovered via Live Debugging)

After analyzing the Walnut Pi's DTB (/boot/sun50i-h616-walnutpi-1b.dtb):

Problem: The mali-supply property points to the wrong regulator:

&gpu {
    mali-supply = <0x0d>;  // WRONG: Points to dcdc3 (vdd-dram)
    status = "okay";
};

Correct Configuration:

&gpu {
    mali-supply = <&reg_dcdc1>;  // CORRECT: Points to dcdc1 (vdd-gpu-sys)
    status = "okay";
};

AXP313A PMIC Regulator Map (Confirmed from Orange Pi Zero 3 DTS)

The H618 uses AXP313A PMIC (same as Orange Pi Zero 2W/3):

Regulator DT Name Voltage Purpose
dcdc1 vdd-gpu-sys 810mV - 990mV GPU (Mali-G31 MP2)
dcdc2 vdd-cpu 810mV - 1100mV CPU
dcdc3 vdd-dram 1100mV DRAM
aldo1 vcc1v8 1800mV VCC-PLL, VCC-IO
dldo1 vcc3v3 3300mV VCC-IO, WiFi, Ethernet

Source: https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/allwinner/sun50i-h618-orangepi-zero3.dts

PRCM Power Domain (Critical for GPU)

  • Register: 0x7010254 (PRCM block at 0x7010000)
  • Value: Write 0x0 to enable GPU power domain
  • Location in U-Boot: arch/arm/mach-sunxi/clock_sun50i_h6.c
  • Mainline Kernel: Added in Linux 6.15 via sun50i-h6-prcm-ppu driver
  • Backport for 6.12: Use patch from Armbian/build

Exact DTB Fix Needed

// In sun50i-h618-walnutpi-zerow.dts:

#include "sun50i-h616.dtsi"
#include "sun50i-h616-cpu-opp.dtsi"

&gpu {
    compatible = "allwinner,sun50i-h616-mali", "arm,mali-bifrost";
    reg = <0x0 0x1800000 0x0 0x40000>;
    interrupts = <GIC_SPI 90 IRQ_TYPE_LEVEL_HIGH>;
    clocks = <&ccu CLK_BUS_GPU>, <&ccu CLK_GPU>;
    clock-names = "bus", "core";
    resets = <&ccu RST_BUS_GPU>;
    operating-points-v2 = <&gpu_opp_table>;
    mali-supply = <&reg_dcdc1>;  // Must use dcdc1 (vdd-gpu-sys)
    status = "okay";
};

&r_i2c {
    status = "okay";

    axp313: pmic@36 {
        compatible = "x-powers,axp313a";
        reg = <0x36>;
        #interrupt-cells = <1>;
        interrupt-controller;
        interrupt-parent = <&pio>;
        interrupts = <2 9 IRQ_TYPE_LEVEL_LOW>;  /* PC9 */

        regulators {
            reg_dcdc1: dcdc1 {
                regulator-always-on;
                regulator-min-microvolt = <810000>;
                regulator-max-microvolt = <990000>;
                regulator-name = "vdd-gpu-sys";  // GPU supply!
            };

            reg_dcdc2: dcdc2 {
                regulator-name = "vdd-cpu";
            };

            reg_dcdc3: dcdc3 {
                regulator-name = "vdd-dram";  // WRONG for mali-supply!
            };
        };
    };
};

Kernel Version Requirements for Panfrost

Feature Minimum Version Status
Panfrost Bifrost (Mali-G31) 6.1+ ✅ Works
H618 DTS support 6.8+ ✅ Mainline
GPU OPP table 6.8+ ✅ Mainline
PRCM power domain driver 6.15+ ⚠️ Backport needed for 6.12
sun50i-h6-prcm-ppu.ko 6.15+ ⚠️ Use patch for 6.12

Required Kernel Patches (from Armbian/build)

  1. GPU Node: arm64-dts-allwinner-sun50i-h616-Add-GPU-node.patch
    • Source: patch/kernel/archive/sunxi-6.12/
  2. GPU Enable: arm64-dts-sun50i-h618-orangepi-zero2w-Enable-GPU-mali.patch
  3. PRCM Power Domain: clk-sunxi-ng-h6-r-add-GPU-power-domain.patch
    • Source: patch/kernel/archive/sunxi-6.13/patches.armbian/
  4. AXP313A Support: arm64-dts-allwinner-Add-axp313a.dtsi.patch
  5. Missing Nodes: arm64-dts-sun50i-h618-orangepi-zero2w-Add-missing-nodes.patch

5. PMIC

Type: AXP313A (Confirmed)

  • Manufacturer: X-Powers
  • I2C Address: 0x36 (same as AXP305/AXP805/AXP806)
  • Driver: axp20x (mainline kernel)
  • DTS Compatible: "x-powers,axp313a"

Regulator Configuration (Full DTS)

&r_i2c {
    status = "okay";

    pmic@36 {
        compatible = "x-powers,axp313a";
        reg = <0x36>;
        #interrupt-cells = <1>;
        interrupt-controller;
        interrupt-parent = <&pio>;
        interrupts = <2 9 IRQ_TYPE_LEVEL_LOW>;  /* PC9 */

        vin1-supply = <&reg_vcc5v>;
        vin2-supply = <&reg_vcc5v>;
        vin3-supply = <&reg_vcc5v>;

        regulators {
            /* Supplies VCC-PLL, so needs to be always on. */
            reg_aldo1: aldo1 {
                regulator-always-on;
                regulator-min-microvolt = <1800000>;
                regulator-max-microvolt = <1800000>;
                regulator-name = "vcc1v8";
            };

            /* Supplies VCC-IO, so needs to be always on. */
            reg_dldo1: dldo1 {
                regulator-always-on;
                regulator-min-microvolt = <3300000>;
                regulator-max-microvolt = <3300000>;
                regulator-name = "vcc3v3";
            };

            reg_dcdc1: dcdc1 {
                regulator-always-on;
                regulator-min-microvolt = <810000>;
                regulator-max-microvolt = <990000>;
                regulator-name = "vdd-gpu-sys";  // GPU!
            };

            reg_dcdc2: dcdc2 {
                regulator-always-on;
                regulator-min-microvolt = <810000>;
                regulator-max-microvolt = <1100000>;
                regulator-name = "vdd-cpu";
            };

            reg_dcdc3: dcdc3 {
                regulator-always-on;
                regulator-min-microvolt = <1100000>;
                regulator-max-microvolt = <1100000>;
                regulator-name = "vdd-dram";
            };
        };
    };
};

Reference: https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/allwinner/sun50i-h618-orangepi-zero3.dts

6. Device Support Matrix

Device Status Notes
Boot ✅ Working Vendor U-Boot required (boot.bin on SD card)
UART ✅ Working /dev/ttyS0 at 115200 baud (serial console)
WiFi ✅ Working UWE5622, modules: sprdwl_ng, sprdbt_tty
Bluetooth ✅ Working Part of UWE5622, module: sprdbt_tty
Ethernet ✅ Working Via AC200 EPHY, 100Mbps, PHY: motorcomm or internal
HDMI ✅ Working On vendor kernel (6.1.31), mainline 6.12+ for H618
GPU/Panfrost ⚠️ Needs fix mali-supply → dcdc1, PRCM register 0x7010254
USB (OTG) ✅ Working 1x USB-C at usbphy0
USB (Host) ✅ Working 2x USB 2.0 via FPC expansion connector
SPI Flash ✅ Working Optional 2MB NOR for boot (unpopulated by default)
Audio ✅ Working Via expansion board, 3.5mm jack
GPIO ✅ Working 40-pin header, Raspberry Pi compatible
CPU Frequency ✅ Working OPP table available, up to 1.5GHz
Thermal ✅ Working THS sensor, requires sun50i-h5-ths2.dtso overlay

7. Recommended Armbian Implementation Path

7.1 Board Configuration

Create config/boards/walnutpi-zerow.csc (CSC = Community Supported Configuration):

# File: config/boards/walnutpi-zerow.csc
# Walnut Pi Zero W - Allwinner H618
BOARD_NAME="Walnut Pi Zero W"
BOARD_VENDOR="Walnut"
BOARDFAMILY="sun50iw9"  # Same as Orange Pi Zero 2W
BOARD_MAINTAINER="community"
INTRODUCED="2024"
BOOTCONFIG="walnutpi_zerow_defconfig"
BOOTBRANCH="tag:v2024.01"
BOOTPATCHDIR="v2024-sunxi"
BOOT_LOGO="desktop"
OVERLAY_PREFIX="sun50i-h616"  # Same as Orange Pi Zero 2W
KERNEL_TARGET="current,edge"
KERNEL_TEST_TARGET="current"
FORCE_BOOTSCRIPT_UPDATE="yes"

# WiFi/BT modules (same as Orange Pi Zero 2W)
MODULES_CURRENT="uwe5622_bsp_sdio sprdwl_ng sprdbt_tty"
MODULES_EDGE="uwe5622_bsp_sdio sprdwl_ng sprdbt_tty"
MODULES_BLACKLIST_CURRENT="bcmdhd"

# Enable UWE5622 extension
enable_extension "uwe5622-allwinner"

7.2 U-Boot Implementation

  1. Create defconfig: configs/walnutpi_zerow_defconfig

    • Base on orangepi_zero3_defconfig
    • Adjust for Walnut Pi specific features

  2. Create DTS: arch/arm/dts/sun50i-h618-walnutpi-zerow.dts

    • Adapt from sun50i-h618-orangepi-zero3.dts
    • Update model and compatible strings: 
      model = "Walnut Pi Zero W";
compatible = "walnut,walnutpi-zerow", "allwinner,sun50i-h618";

  3. Apply Patches:

    • GPU enable hack: allwinner-h616-GPU-enable-hack.patch
    • THS workaround: allwinner-h616-THS-workaround.patch

7.3 Kernel Implementation

  1. Base DTS: Copy from Orange Pi Zero 2W/3

    • Source: arch/arm64/boot/dts/allwinner/sun50i-h618-orangepi-zero3.dts
    • Rename to: sun50i-h618-walnutpi-zerow.dts

  2. Fix GPU Node (Critical):

    &gpu {
    mali-supply = <&reg_dcdc1>;  // vdd-gpu-sys, NOT dcdc3!
    status = "okay";
};

  3. Apply Kernel Patches (from patch/kernel/archive/sunxi-6.12/ or sunxi-6.13/):

    • arm64-dts-allwinner-sun50i-h616-Add-GPU-node.patch
    • arm64-dts-sun50i-h618-orangepi-zero2w-Enable-GPU-mali.patch
    • clk-sunxi-ng-h6-r-add-GPU-power-domain.patch (for 6.12)
    • sound-for-h616-h618-Allwinner-SoCs.patch (HDMI audio)

7.4 What Can Be Upstreamed to kernel.org

  1. New DTS: sun50i-h618-walnutpi-zerow.dts

    • Can be submitted to mainline Linux
    • Based on existing H618 DTS patterns

  2. GPU Fix: The mali-supply fix is board-specific

    • Should be included in the new DTS submission

  3. Already Upstream (no need to upstream again):

    • H618 SoC support (sun50i-h616.dtsi)
    • AXP313A PMIC driver
    • Panfrost Bifrost support
    • Orange Pi Zero 2W/3 DTS (reference implementations)

8. References

Walnut Pi Resources

Armbian Resources

Mainline Kernel/Upstream

U-Boot Upstream

Linux-Sunxi Community

Debugging Session Findings (This Document's Source)

9. Next Steps for Armbian Developer

  1. Create board config:

    • Copy orangepizero2w.csc → walnutpi-zerow.csc
    • Update BOARD_NAME, BOARD_VENDOR, BOOTCONFIG

  2. Add U-Boot support:

    • Create walnutpi_zerow_defconfig (base on orangepi_zero3_defconfig)
    • Create DTS: sun50i-h618-walnutpi-zerow.dts
    • Apply GPU enable patch

  3. Add Kernel support:

    • Create DTS in arch/arm64/boot/dts/allwinner/
    • Fix GPU node (mali-supply = <&reg_dcdc1>)
    • Apply required kernel patches from sunxi-6.12/ or sunxi-6.13/

  4. Test:

    • Boot from SD card
    • Verify Panfrost: GALLIUM_DRIVER=panfrost glxinfo | grep "OpenGL renderer"
    • Expected output: OpenGL renderer string: Mali-G31 (Panfrost)

  5. Submit PR to https://github.com/armbian/build with:

    • Board config file
    • U-Boot defconfig and DTS
    • Kernel DTS and patches
    • This documentation as reference

Document Prepared By: OpenCode debugging session (2026-05-03)
Based On: Live analysis of Walnut Pi Zero W running official image (kernel 6.1.31)
Reference Hardware: Orange Pi Zero 2W (same H618 SoC)
GitHub Issue: walnutpi/walnutpi-build#12
Armbian Issue: #9749

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