Display - Qualcomm Dragonwing Documentation

The IQ-9075 platform features a Qualcomm Adreno Display Processing Unit (DPU) providing hardware-accelerated image processing. The IQ9-EVK supports two simultaneous displays via dual DisplayPort outputs.

Display Capabilities

Interface	Capability
DP0	3840 × 2160 at 60 fps, 30 bpp
DP1	3840 × 2160 at 60 fps, 30 bpp
Concurrent	DP0 as primary + DP1 as secondary, both at 3840 × 2160 @ 60 fps

Supported features:

Wayland and Weston with upstream protocol
Weston compositor with DRM backend
2× DisplayPort with SST and MST support

Architecture

DPU Hardware

Component	Function
Bus Interface	Fetches data from memory
Source Surface Processing	Reads RGB/YUV surfaces; performs format conversion
Blending	Blends and mixes source surfaces
Destination Surface Processing	Converts and adjusts data for panel characteristics
Compression	Reduces bandwidth by sending compressed display buffers
Display Interface	Generates timings for connected display peripherals

Software Stack

Component	Description
Wayland Sink	Plug-in communicating with Weston to render the display
Weston	Wayland compositor; handles composition and rendering
DRM Backend	Manages Adreno DPU hardware resources and composition strategy
libdrm	Library providing DRM IOCTL APIs
DRM/KMS Framework	Kernel and userland interface for hardware features
Adreno DPU Driver	Manages all pixel data paths to panel interfaces

DisplayPort and DSI Interfaces

eDP Interface

The processor has four eDP interfaces. eDP0 and eDP1 are routed to connectors JEDP0 and JEDP1.

DSI Interface

The IQ-9075 supports two 4-lane MIPI-DSI with VESA DSC v1.2. The DSI0 interface uses an analog switch allowing access through both the JDISP LCD connector and the JEXP1 board-to-board expansion connector.

Setup

Connect DisplayPort

Connect primary display

Connect a DisplayPort cable to the eDP0 connector.

Connect secondary display (optional)

For dual display, connect a second DisplayPort cable to eDP1.

Power on

Power on the device. Weston launches automatically during boot and displays the flower pattern.

SSH Access

Default credentials: Username: ubuntu / Password: ubuntu

Testing and Verification

Run Weston EGL Client

weston-simple-egl

Expected output: A rotating triangle on the display at 60 fps.

300 frames in 5 seconds: 60.000000 fps

Press Ctrl+C to terminate.

GStreamer Video Playback

Ensure video files are at /etc/media on the device.

# H.264 playback
gst-launch-1.0 -v filesrc location=/etc/media/video.mp4 ! qtdemux ! queue ! \
  h264parse ! v4l2h264dec capture-io-mode=4 output-io-mode=4 ! \
  video/x-raw,format=NV12 ! waylandsink

# H.265/HEVC playback
gst-launch-1.0 -v filesrc location=/etc/media/video_hevc.mp4 ! qtdemux ! queue ! \
  h265parse ! v4l2h265dec capture-io-mode=4 output-io-mode=4 ! \
  video/x-raw,format=NV12 ! waylandsink

# With scaling
gst-launch-1.0 -v filesrc location=/etc/media/video.mp4 ! qtdemux ! queue ! \
  h264parse ! v4l2h264dec capture-io-mode=4 output-io-mode=4 ! \
  video/x-raw,width=1920,height=1080 ! waylandsink

Key pipeline components:

Component	Purpose
`capture-io-mode=4`	Allocates decoded frames as DMABUF (zero-copy to display)
`output-io-mode=4`	Handles encoded bitstream buffers via DMABUF
`format=NV12`	NV12 pixel format for hardware-accelerated path
`waylandsink`	Renders video to Wayland display

Debugging

Check DisplayPort Status

# Cable status
sudo cat /sys/class/drm/card0-DP-1/status   # eDP0
sudo cat /sys/class/drm/card0-DP-2/status   # eDP1

# Available modes (EDID)
sudo cat /sys/class/drm/card0-DP-1/modes

# Detailed DP info
sudo cat /sys/kernel/debug/dri/0/DP-1/dp_debug

Debug Filesystem

Command	Purpose
`dmesg \| grep -i display`	Display-related kernel messages
`dmesg \| grep -i drm`	DRM subsystem messages
`cat /sys/kernel/debug/dri/0/state`	Current DRM state
`cat /proc/interrupts \| grep mdss`	Display interrupts

Troubleshooting

No Display Output (Black Screen)

cat /sys/class/drm/card0-DP-1/status
sudo dmesg | grep -i "dp\|display\|drm"

Verify cable connection to eDP0 or eDP1
Check display power and input source selection

Incorrect Resolution

cat /sys/class/drm/card0-DP-1/modes

Verify the display supports the desired resolution.

Weston Fails to Start

journalctl -u weston
ls -l /dev/dri/card0
ls -l /dev/dri/

Manually launch Weston with debug output:

weston --idle-time=0 --continue-without-input --log=/home/ubuntu/weston.log

Dual Display Not Working

cat /sys/class/drm/card0-DP-1/status
cat /sys/class/drm/card0-DP-2/status
cat /sys/kernel/debug/dri/0/state

Verify both cables are connected to eDP0 and eDP1
Check Weston configuration for multi-display support

XWayland / Weston Needs Restart

ps -A | grep weston
killall weston
sudo systemctl start weston-autostart
export XDG_RUNTIME_DIR=/run/user/$(id -u ubuntu)
export WAYLAND_DISPLAY=wayland-1

Resources

Resource	URL
DRM Internals	https://www.kernel.org/doc/html/v5.4/gpu/drm-internals.html
Kernel Mode Setting (KMS)	https://www.kernel.org/doc/html/v5.4/gpu/drm-kms.html
Wayland Protocol	https://wayland.freedesktop.org/
Weston Compositor	https://gitlab.freedesktop.org/wayland/weston
GStreamer Documentation	https://gstreamer.freedesktop.org/documentation/

​Display Capabilities

​Architecture

​DPU Hardware

​Software Stack

​DisplayPort and DSI Interfaces

​eDP Interface

​DSI Interface

​Setup

​Connect DisplayPort

​SSH Access

​Testing and Verification

​Run Weston EGL Client

​GStreamer Video Playback

​Debugging

​Check DisplayPort Status

​Debug Filesystem

​Troubleshooting

​Resources