Orange Pi 6 Plus GPU — Mali-G720 Immortalis MC10

Enabling the Mali-G720 Immortalis MC10 (Panthor) GPU on the Orange Pi 6 Plus (CIX CD8180 / Sky1 SoC) under mainline Linux. This document covers our full reverse engineering process, the root cause of GPU power failure on ACPI boot, and how to get a working GPU using device tree boot with the Sky1-Linux kernel.

Quick Start

→ Pre-built Sky1-Linux Kernel Downloads — kernel, modules, DTB, and firmware ready to install.

Then create a GRUB entry from gpu/grub/06_sky1 and reboot.

Status: ✅ GPU Working

panthor 15000000.gpu: [drm] clock rate = 900000000
panthor 15000000.gpu: [drm] GPU DVFS: 6 OPPs from SCMI perf domain
panthor 15000000.gpu: [drm] Mali-G720-Immortalis id 0xc870
panthor 15000000.gpu: [drm] shader_present=0x550555 l2_present=0x1 tiler_present=0x1

Detail	Value
Kernel	6.19.0-rc8-sky1-rc.r6 (Sky1-Linux RC track)
Boot mode	Device tree (`acpi=off`)
DRM render	`/dev/dri/renderD128`
Display	HDMI via Linlon-D60 + Trilin-DPSUB + PS185 DP-to-HDMI bridge
OpenGL ES	3.1 (Panfrost, Mesa 25.3.3)
Vulkan	1.4.328 (panvk, Mesa 25.3.3)
GPU clock	900 MHz, 6 DVFS operating points
Shader cores	10 (MC10 configuration)

The Problem
Mapping the Power Architecture
Exploring Every ACPI Path
The Breakthrough: TF-A's Dual Code Path
Device Tree Boot on Armbian
Sky1-Linux: The Complete Solution
How to Install
Boot Configuration
Kernel Config Options
Verification
Benchmarks
Known Issues
Hardware Reference
What's in This Repo
License & Attribution

The Problem

The Orange Pi 6 Plus ships with CIX's vendor kernel (6.6-cix) and a proprietary out-of-tree mali_kbase driver. On a mainline Armbian kernel (6.18.x), the Mali-G720 GPU at MMIO address 0x15010000 is completely unreachable. Any attempt to read GPU registers — even the basic GPU_ID — results in a Bus Error that can cascade into a stuck process and system hang.

The mainline Panthor driver (in-tree since kernel 6.10) supports Mali-G720, but it only has an of_match_table (device tree) — no ACPI match. On Armbian's default ACPI boot, the driver never probes.

We set out to understand why the GPU couldn't power on and whether we could fix it.

Step 1: Mapping the Power Architecture

We reverse-engineered the GPU power control path. The CIX CD8180 uses ARM's RCSU (Reset and Clock Supervision Unit) with DMRP (Domain Resource Power) registers to manage power partitions:

Address	Register	Access from EL1	Purpose
0x15000010	RCSU PASS	✅ Readable	Power status readback
0x15000014	RCSU ENBL	❌ Firewalled	Power enable — the critical register
0x15000018	RCSU BUSY	✅ Readable	Power transition status
0x15000218	RCSU MSK0	✅ Readable	Clock/partition mask
0x15010000	GPU_ID	❌ Bus Error	Mali GPU ID — unreachable when unpowered
0x16000400	SRC DOMAIN_0	✅ Read/Write	Reset control — bit 6 = GPU
0x16000504	MVCK	❌ Firewalled	Validation gate, always reads 0

The critical finding: RCSU ENBL at +0x14 is the power-on switch, but it's firewalled from EL1. The OS kernel cannot write it directly. Only EL3 (TF-A secure world) can touch it.

Step 2: Exploring Every ACPI Path

Since the board boots with ACPI by default, we systematically tried every possible ACPI mechanism to power the GPU. We built diagnostic kernel modules for each approach (see modules/):

ACPI `GPUP._ON` Method

The ACPI tables define a power resource for the GPU that calls into DMRP. But the DMRP path is gated by the MVCK register at 0x16000504, which always reads zero and is firewalled. Dead end.

ACPI DSM (Device Specific Method)

CIX's kernel source references a cix_acpi_pd.c GUID for ACPI power domain management. We checked: the DSM does not exist on the Generic BIOS v1.3 firmware. Dead end.

SCMI Power Protocol via TF-A

The ARM SCMI interface exposes 22 power domains through SMC call 0xc2000001. Domain 21 (gpu_pd) accepts SET requests and returns success (0). But the GPU stays dead. The SET is bookkeeping only — it never writes hardware registers. Dead end.

SCMI Power Protocol via SCP

We tried reaching the System Control Processor's SCMI endpoint directly via the mailbox transport. The SCP does not expose the POWER protocol at all — request DENIED (-8). Dead end.

SCMI Clocks

GPU PLLs are running (1 GHz core clock, 900 MHz top clock visible in SCMI clock enumeration). The hardware is clocked — it's just not powered. Confirmed clocks are not the issue.

Reset Controller

Sky1's reset-sky1 driver probes for ACPI ID CIXHA020, but the vendor RSTL ACPI binding isn't in mainline. reset_control_get() returns -ENOENT. Dead end.

Direct Reset Deassert

We wrote a diagnostic module to directly write the SRC (System Reset Controller) domain register. Bit 6 at offset 0x400 controls GPU reset. We successfully deasserted GPU reset — confirmed by readback — but without power, it accomplished nothing. Proved reset works, but power is the blocker.

Diagnostic Modules

Module	What It Does
`gpu_power_diag.c`	Enumerates all 22 TF-A power domains, tests SET, safe GPU register read
`gpu_reset_deassert.c`	Direct SRC register write to deassert GPU reset (bit 6) — confirmed working
`gpu_acpi_poweron.c`	Triggers ACPI `PPRS._ON` via `acpi_device_set_power()`
`gpu_dsm_poweron.c`	ACPI DSM attempt — confirmed DSM doesn't exist on this firmware
`gpu_clk_enable.c`	Raw SCMI mailbox clock enable attempt

Step 3: The Breakthrough — TF-A's Dual Code Path

After exhausting every ACPI path, we examined the behavior difference between ACPI and device tree boot at the firmware level. The same SMC call (0xc2000001) goes to the same TF-A handler, but the handler has two code paths:

Boot Mode	SCMI Power SET Behavior	Hardware Effect
ACPI	Software bookkeeping only — returns success	GPU stays unpowered
Device Tree	Writes RCSU DMRP ENBL register at EL3	GPU powers on

This is the root cause. On ACPI boot, TF-A's SCMI power handler is effectively a stub. On DT boot, TF-A performs the actual EL3 register write to RCSU ENBL at +0x14, powering on the GPU partition.

The fix was not a kernel hack — it was switching boot modes.

Full ACPI Failure Summary

Layer	What Happens	Why It Fails
ACPI `GPUP._ON`	Calls DMRP to power GPU	DMRP gated by MVCK (0x16000504), always 0, firewalled
ACPI DSM	Would use `cix_acpi_pd.c` GUID	DSM does not exist on Generic BIOS v1.3
TF-A SCMI Power	Domain 21 (`gpu_pd`) SET succeeds	Software-only bookkeeping — never writes DMRP registers
SCP SCMI Power	Mailbox transport	POWER protocol not exposed — request DENIED (-8)
SCMI Clocks	GPU PLLs running (1 GHz, 900 MHz)	Consumers not registered in kernel on ACPI boot
Reset control	`reset-sky1` for CIXHA020	Vendor `RSTL` binding not in mainline — returns -ENOENT
Panthor driver	`of_match_table` only	No ACPI match — driver never probes
RCSU DMRP	ENBL at +0x14	Firewalled from EL1; only EL3 can write

Step 4: Device Tree Boot on Armbian

With the root cause understood, the fix was straightforward: boot with acpi=off and provide a proper device tree blob. But the stock Armbian kernel was missing critical platform drivers needed for DT boot:

RESET_SKY1 — Sky1 reset controller
PINCTRL_SKY1 — Sky1 pin controller
PCI_SKY1 — Sky1 PCIe host (needed for ethernet, NVMe)
PHY_CIX_PCIE — CIX PCIe PHY

Without these, a DT boot attempt left the board dead — no network, no storage. The mainline kernel config has CONFIG_ARCH_CIX=n — everything CIX is disabled.

We could rebuild the kernel with these options enabled, but we'd still be missing the display drivers (Linlon-D60, Trilin-DPSUB), GPU DVFS integration, and the Orange Pi 6 Plus-specific device tree with corrected GPIO assignments and the DP-to-HDMI bridge chain.

Step 5: Sky1-Linux — The Complete Solution

Sky1-Linux maintains a 40-patch kernel series (GPL-2.0) on top of mainline Linux that enables the full CIX CD8180 platform. Their work provides everything needed beyond what we established through reverse engineering:

What our research established:

The GPU power architecture (RCSU DMRP registers, EL1 firewalls)
The TF-A dual code path (ACPI = stub, DT = real power-on)
That acpi=off with device tree boot is mandatory
Which platform drivers are required (RESET_SKY1, PINCTRL_SKY1, PCI_SKY1, PHY_CIX_PCIE)
That the SCMI power domain, clocks, and reset are all functional — the only missing piece was TF-A's ACPI-mode stub

What Sky1-Linux provides:

Panthor DVFS — SCMI performance domain integration for dynamic GPU frequency/voltage scaling (6 OPPs up to 900 MHz)
Display stack — Linlon-D60 display controller, Trilin-DPSUB DisplayPort transmitter
DP-to-HDMI bridge — PS185 converter support (critical for HDMI output on the Orange Pi 6 Plus)
Platform drivers — RESET_SKY1, PINCTRL_SKY1, PCI_SKY1, PHY_CIX_PCIE
Orange Pi 6 Plus device tree — Board-specific GPIO assignments, USB-C DP alt-mode, PCIe power
Peripherals — RTL8126 5GbE, RTL8125 2.5GbE, HDA + DSP audio, VPU video codecs
Firmware — Mali CSF firmware (ARM Ltd), DSP/VPU firmware (CIX) via sky1-firmware

We copied the Sky1-Linux kernel, modules, device tree, and firmware to our Armbian NVMe install. Created a custom GRUB entry with acpi=off and an explicit devicetree directive. First boot: Panthor loaded, GPU_ID read successfully, CSF firmware loaded, /dev/dri/renderD128 appeared.

GPU Power-On Chain (Device Tree Boot)

GRUB loads DTB (sky1-orangepi-6-plus.dtb)
  → Kernel boots with acpi=off, parses device tree
    → Panthor driver probes GPU node (compatible = "arm,mali-valhall-csf")
      → Requests power domain ON via ARM SCMI
        → SCMI message sent to TF-A via SMC 0xc2000001
          → TF-A writes RCSU DMRP ENBL register (0x15000014) at EL3
            → GPU power partition activates
              → Panthor reads GPU_ID @ 0x15010000 = 0xc870 (Mali-G720)
                → CSF firmware loaded (mali_csffw.bin)
                  → GPU operational, /dev/dri/renderD128 created

Firmware Dependencies

The GPU requires proprietary firmware not available in mainline Linux:

File	Vendor	Purpose
`arm/mali/arch12.8/mali_csffw.bin`	ARM Ltd	Mali CSF (Command Stream Frontend) firmware
`dsp_fw.bin`	CIX Technology	Tensilica HiFi5 audio DSP firmware
`*.fwb` (h264dec, hevcdec, av1dec, etc.)	CIX Technology	VPU video codec firmware

All firmware is proprietary but redistributable. Pre-built copies are in downloads/.

How to Install

Option 1: Use Pre-Built Files from This Repo (Fastest)

See downloads/README.md for the full file listing and copy commands. Summary:

VERSION="6.19.0-rc8-sky1-rc.r6"

# Kernel, initrd, config
sudo cp downloads/$VERSION/boot/vmlinuz-* /boot/
sudo cp downloads/$VERSION/boot/initrd.img-* /boot/
sudo cp downloads/$VERSION/boot/config-* /boot/

# Device tree
sudo mkdir -p /boot/dtb
sudo cp downloads/$VERSION/boot/dtb/*.dtb /boot/dtb/

# Modules
sudo cp -a downloads/$VERSION/lib-modules-* /lib/modules/
sudo depmod -a $VERSION

# Firmware
sudo cp -a downloads/$VERSION/firmware/arm /lib/firmware/
sudo cp downloads/$VERSION/firmware/dsp_fw.bin /lib/firmware/
sudo cp downloads/$VERSION/firmware/*.fwb /lib/firmware/

Option 2: Install via Sky1-Linux APT

wget -qO- https://sky1-linux.github.io/apt/key.gpg | sudo tee /usr/share/keyrings/sky1-linux.asc > /dev/null
echo "deb [signed-by=/usr/share/keyrings/sky1-linux.asc] https://sky1-linux.github.io/apt sid main non-free-firmware" | \
  sudo tee /etc/apt/sources.list.d/sky1-linux.list
sudo apt update && sudo apt install sky1-minimal

Option 3: Build from Source

git clone https://github.com/Sky1-Linux/linux-sky1.git
cd linux-sky1
wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.18.9.tar.xz
tar xf linux-6.18.9.tar.xz && cd linux-6.18.9
for p in ../patches/*.patch; do patch -p1 < "$p"; done
cp ../config/config.sky1 .config
make ARCH=arm64 olddefconfig
make ARCH=arm64 -j$(nproc) Image modules dtbs

Boot Configuration

⚠️ acpi=off is mandatory. Without it, the GPU will not power on.

Create a GRUB entry (see gpu/grub/06_sky1 for a complete template):

menuentry "Sky1 Linux (GPU+NPU)" {
    search --no-floppy --fs-uuid --set=root YOUR-ROOT-UUID
    linux /boot/vmlinuz-6.19.0-rc8-sky1-rc.r6 root=UUID=YOUR-ROOT-UUID ro \
        acpi=off clk_ignore_unused linlon_dp.enable_fb=1 \
        linlon_dp.enable_render=0 fbcon=map:01111111 rootwait
    initrd /boot/initrd.img-6.19.0-rc8-sky1-rc.r6
    devicetree /boot/dtb/sky1-orangepi-6-plus.dtb
}

Boot parameters:

Parameter	Purpose
`acpi=off`	Critical. Forces device tree boot so TF-A powers the GPU
`clk_ignore_unused`	Prevents kernel from disabling clocks that appear unused
`linlon_dp.enable_fb=1`	Enable framebuffer on Linlon display controller
`linlon_dp.enable_render=0`	Disable render mode (use GPU for acceleration)
`fbcon=map:01111111`	Map virtual consoles to framebuffer
`rootwait`	Wait for root device (NVMe)

Required Kernel Config Options

If building from source, these are the critical options:

Architecture & Platform

CONFIG_ARCH_CIX=y           # CIX CD8180 SoC support
CONFIG_RESET_SKY1=y         # Sky1 reset controller
CONFIG_PINCTRL_SKY1=y       # Sky1 pin controller
CONFIG_PCI_SKY1=y           # Sky1 PCIe host controller
CONFIG_PHY_CIX_PCIE=y       # CIX PCIe PHY
CONFIG_CIX_MBOX=y           # CIX mailbox (SCMI transport)

GPU & Display

CONFIG_DRM_PANTHOR=m         # Mali Panthor GPU driver (mainline)
CONFIG_DRM_CIX=m             # CIX display subsystem
CONFIG_DRM_LINLONDP=m        # Linlon-D60 display controller
CONFIG_DRM_TRILIN_DP_CIX=m   # Trilin DisplayPort (generic)
CONFIG_DRM_TRILIN_DPSUB=m    # Trilin DisplayPort sub-driver

Verification

After booting with acpi=off:

# GPU detected?
dmesg | grep panthor
# → panthor 15000000.gpu: [drm] Mali-G720-Immortalis id 0xc870

# Render node present?
ls /dev/dri/renderD128
# → /dev/dri/renderD128

# GPU modules loaded?
lsmod | grep -E 'panthor|linlon|trilin'

# Vulkan working?
vulkaninfo --summary 2>&1 | grep deviceName
# → deviceName = Mali-G720

# OpenGL ES benchmark (requires connected display)
glmark2-es2-drm --winsys-options "drm-device=/dev/dri/card5"

Benchmarks

glmark2 — OpenGL ES 3.1, 1920×1080 HDMI

Baseline run (full suite):

Scene	FPS	Scene	FPS
texture nearest	5,848	bump normals	5,847
build (VBO)	5,388	conditionals (base)	5,263
pulsar	5,142	function (low)	4,866
shading gouraud	4,653	shading phong	3,726
effect2d 3×3	3,907	build (no VBO)	3,386
terrain	3,201	jellyfish	3,201
desktop shadow	2,974	refract	2,636
ideas	2,274	effect2d 5×5	1,690
desktop blur	702	terrain (heavy)	130

Recent run (2026-02-13, partial):

kmscube -c 600: ~59.99 fps (vsync-limited)
glmark2-es2-drm --winsys-options drm-device=/dev/dri/card5 -b refract --off-screen:
- refract FPS: 172
- glmark2 Score: 171

Proper rerun (2026-02-13, full suite, executed from VT2):

Command:
- glmark2-es2-drm --winsys-options drm-device=/dev/dri/card5
Output file: /tmp/glmark2-fullsuite-vt2-20260213-090142.txt
glmark2 Score: 3079
Surface: 1920×1080 fullscreen
Selected scenes (FPS):
- build use-vbo=true: 4376
- texture nearest: 4712
- bump normals: 5933
- pulsar: 4217
- desktop blur: 659
- desktop shadow: 2736
- ideas: 2003
- jellyfish: 2831
- terrain <default>: 84 (note: baseline table lists terrain (heavy); not directly comparable)
- refract: 186 (note: baseline table lists 2636 FPS; likely captured under different conditions or needs revalidation)

Notes:

If you see Failed to become DRM master (hint: glmark2-drm needs to be run in a VT), rerun from a real VT / console session so the benchmark can take DRM master cleanly.
PanVK Vulkan compute offload is currently unstable for large workloads (OOM / DeviceLost). llama-bench-vulkan only succeeds with very small batches/prompts so far.

Vulkan Buffer Bandwidth

Test	Throughput
Buffer Fill (256 MB)	37.4 GB/s
Buffer Copy (256 MB)	21.4 GB/s

GPU vs NPU Comparison

Component	Model	Benchmark	Result
GPU	Mali-G720 MC10	Vulkan fill	37.4 GB/s
GPU	Mali-G720 MC10	OpenGL ES (peak)	5,848 FPS @ 1080p
NPU	Zhouyi Z3	CLIP Text inference	58.2 inf/s (17.2 ms)
NPU	Zhouyi Z3	CLIP Visual inference	60.1 inf/s (16.6 ms)
NPU	Zhouyi Z3	YOLOv8n detection	58.9 inf/s (17.0 ms)

GPU for graphics and general compute. NPU for dedicated AI inference. See NPU repository.

Known Issues

Issue	Impact	Workaround
GPU thermal sensors return err=-2	Cosmetic (no temperature monitoring)	None needed — GPU runs fine
ACPI boot cannot power GPU	No GPU without `acpi=off`	Use device tree boot
Display hotplug unreliable	Display may not detect if plugged in after boot	Connect before booting
panvk Vulkan non-conformant	May fail edge-case CTS tests	Functional for all tested workloads
Killing GPU processes with SIGKILL	Panthor MCU reset fails → GPU unusable	Reboot to recover; let GPU processes exit cleanly

Hardware Reference

Component	Detail
Board	Orange Pi 6 Plus
SoC	CIX CD8180 (Sky1) — reports as "CIX Phecda Board" in DMI
CPU	12 cores — 4× A520 (1.8 GHz) + 8× A720 (2.6 GHz)
RAM	32 GB LPDDR5
GPU	Mali-G720 Immortalis MC10 — 10 shader cores, 900 MHz, ray tracing
NPU	ARM China Zhouyi Z3 — 30 TOPS (3 cores × 4 TECs)
Display	DP via Linlon-D60 + Trilin-DPSUB, HDMI via PS185 bridge
NIC	Intel i226-V × 2 (PCIe, requires `PCI_SKY1` on DT boot)
GPU MMIO	0x15010000 (Bus Error when unpowered — do not read)

Shader Core Layout

shader_present = 0x550555 → 10 shader cores (MC10)
l2_present     = 0x1      → 1 L2 cache slice
tiler_present  = 0x1      → 1 tiling unit

CIX SIP SMC Function Map

0xc2000001  SCMI-SMC (GPU power domain — stub on ACPI, real on DT)
0xc2000002  CIX_SIP_SVC_SET_REBOOT_REASON
0xc2000003  CIX_SIP_DSU_HW_CTL
0xc2000004  CIX_SIP_DSU_SET_PD (L3 cache)
0xc200000c  CIX_SIP_SMMU_GOP_CTRL
0xc200000d  CIX_SIP_CPUFREQ_SUPPORT
0xc200000f  CIX_SIP_DP_GOP_CTRL (Display GOP handoff)
0xc2000010  CIX_SIP_SET_DDRLP (DDR low-power)

What's in This Repo

.
├── README.md                  ← You are here (full documentation)
├── downloads/                 ← Pre-built Sky1-Linux kernel files
│   └── 6.19.0-rc8-sky1-rc.r6/
├── gpu/
│   └── grub/06_sky1           ← GRUB entry template
├── modules/                   ← Diagnostic kernel modules (our ACPI research)
│   ├── gpu_power_diag.c       ← SCMI power domain enumeration
│   ├── gpu_reset_deassert.c   ← Direct SRC register GPU reset
│   ├── gpu_acpi_poweron.c     ← ACPI power resource trigger
│   ├── gpu_dsm_poweron.c      ← ACPI DSM probe (confirmed absent)
│   ├── gpu_clk_enable.c       ← SCMI clock enable attempt
│   └── gpu_poweron.asl        ← ACPI ASL reference
├── patches/                   ← SCMI framework patches (ACPI research)
└── LICENSE

License & Attribution

This project is licensed under the GNU General Public License v2.0.

GPU support is made possible by Sky1-Linux, an independent project providing full hardware support for CIX CD8180 SoC-based boards.

Component	License	Source
Sky1-Linux kernel patches	GPL-2.0	Sky1-Linux/linux-sky1
Panthor GPU driver	GPL-2.0	Mainline Linux (in-tree since 6.10)
Linlon-DP, Trilin-DPSUB	GPL-2.0	Sky1-Linux patches (out-of-tree)
Mali CSF firmware	Proprietary (ARM Ltd)	sky1-firmware
VPU/DSP firmware	Proprietary (CIX)	sky1-firmware

Name		Name	Last commit message	Last commit date
Latest commit History 5 Commits
downloads		downloads
gpu/grub		gpu/grub
modules		modules
patches		patches
LICENSE		LICENSE
README.md		README.md

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