MarkAntony

To get audio working on the Radxa Dragon (QCS6490) when the standard UCM (Use Case Manager) fails, you have to bypass the "official" path and manually bridge the hardware to the software.
Here is the complete summary of the "manual bridge" method developed. I installed Armbian 25.11.1 Edge Image and below is how I fixed HDMI Audio.
 
Step 1: Create the Hardware Bridge Script
This script manually flips the hardware switches in the Qualcomm DSP that route audio to the HDMI/DisplayPort pins.
File: /usr/local/bin/fix-hdmi-audio.sh Command: sudo nano /usr/local/bin/fix-hdmi-audio.sh
Bash
#!/bin/bash
# Wait for hardware to initialize
sleep 2
# Open the HDMI/DP Audio Bridge
amixer -c 0 cset name='DISPLAY_PORT_RX_0 Audio Mixer MultiMedia1' 1
# Set initial hardware volume
amixer -c 0 cset name='stream0.vol_ctrl0 MultiMedia1 Playback Volu' 75%
Make it executable: sudo chmod +x /usr/local/bin/fix-hdmi-audio.sh
Step 2: Create the Systemd Service
This ensures the hardware switches are flipped automatically every time the board boots up.
File: /etc/systemd/system/hdmi-audio.service Command: sudo nano /etc/systemd/system/hdmi-audio.service
Ini, TOML
[Unit]
Description=Fix HDMI Audio Routing
After=sound.target
 
[Service]
Type=oneshot
ExecStart=/usr/local/bin/fix-hdmi-audio.sh
RemainAfterExit=yes
 
[Install]
WantedBy=multi-user.target
Enable it:
Bash
sudo systemctl daemon-reload
sudo systemctl enable hdmi-audio.service
Step 3: Configure the Desktop Audio Sink
Since the system's "Built-in Audio" often defaults to a "Dummy Output" when UCM is broken, we force PulseAudio to create a manual "Sink" pointing directly to the hardware.
File: /etc/pulse/default.pa Command: sudo nano /etc/pulse/default.pa
Add these lines to the very bottom of the file:
Plaintext
# Manually bridge PulseAudio to the working hardware path
load-module module-alsa-sink device=plughw:0,0 sink_name=Manual_HDMI sink_properties=device.description=HDMI_Audio_Output
set-default-sink Manual_HDMI
Step 4: Clean Up UCM (Optional but Recommended)
To stop the "HDMI Audio failure" warnings during boot, you can ensure your UCM files are at least syntactically correct, even if the system ignores them.
File: /usr/share/alsa/ucm2/QCS6490RadxaDra/HiFi.conf
Plaintext
Syntax 2
SectionDevice."HDMI" {
    Comment "HDMI Output"
    Value {
        PlaybackPriority 200
        PlaybackPCM "hw:0,0"
    }
}
SectionVerb {
    EnableSequence []
    DisableSequence []
}
 
Summary of the Audio Path
By following these steps, you have constructed the following data flow:
Hardware: Qualcomm DSP (Card 0, Device 0).
Bridge: amixer opens the path from the CPU to the HDMI port.
ALSA: Provides the plughw:0,0 interface.
PulseAudio: Grabs that interface and names it "HDMI_Audio_Output."
Applications: YouTube/Browsers send audio to the "Default Sink," which is now your working HDMI path.
Now I will put all these commands into a single "one-click" shell script so you can save it as a backup for future installs?
The Radxa Dragon Audio "One-Click" Fix
Create the file: nano fix_audio.sh
Paste the code below.
 
Run it: chmod +x fix_audio.sh && sudo ./fix_audio.sh
Bash
#!/bin/bash
 
echo "🚀 Starting Radxa Dragon QCS6490 Audio Fix..."
 
# 1. Create the Hardware Bridge Script
echo "🔧 Creating hardware bridge script..."
cat <<EOF | sudo tee /usr/local/bin/fix-hdmi-audio.sh > /dev/null
#!/bin/bash
# Wait for hardware to initialize
sleep 2
# Open the HDMI/DP Audio Bridge
amixer -c 0 cset name='DISPLAY_PORT_RX_0 Audio Mixer MultiMedia1' 1
# Set initial hardware volume
amixer -c 0 cset name='stream0.vol_ctrl0 MultiMedia1 Playback Volu' 75%
EOF
 
sudo chmod +x /usr/local/bin/fix-hdmi-audio.sh
 
# 2. Create the Systemd Service
echo "⚙️  Creating boot-time service..."
cat <<EOF | sudo tee /etc/systemd/system/hdmi-audio.service > /dev/null
[Unit]
Description=Fix HDMI Audio Routing
After=sound.target
 
[Service]
Type=oneshot
ExecStart=/usr/local/bin/fix-hdmi-audio.sh
RemainAfterExit=yes
 
[Install]
WantedBy=multi-user.target
EOF
 
# 3. Enable and Start the Service
sudo systemctl daemon-reload
sudo systemctl enable hdmi-audio.service
sudo systemctl start hdmi-audio.service
 
# 4. Configure PulseAudio Sink
echo "🔉 Configuring PulseAudio/PipeWire sink..."
PA_CONFIG="/etc/pulse/default.pa"
if [ -f "$PA_CONFIG" ]; then
    # Check if we already added the fix to avoid duplicates
    if ! grep -q "Manual_HDMI" "$PA_CONFIG"; then
        cat <<EOF | sudo tee -a "$PA_CONFIG" > /dev/null
 
# Manually bridge PulseAudio to the working hardware path
load-module module-alsa-sink device=plughw:0,0 sink_name=Manual_HDMI sink_properties=device.description=HDMI_Audio_Output
set-default-sink Manual_HDMI
EOF
    fi
else
    echo "⚠️ Warning: /etc/pulse/default.pa not found. You may need to manualy add the sink to your specific sound server config."
fi
 
echo "✅ Success! Please reboot to finalize settings."
echo "   After reboot, select 'HDMI_Audio_Output' in Sound Settings if it doesn't auto-switch."
Why this works for your specific board:
This script performs a "Direct Injection." Instead of asking the operating system to figure out where the audio goes (which fails because the Qualcomm UCM profiles are currently buggy), it tells the hardware exactly which gate to open and tells the software exactly which "sink" to pour the audio into.