🛠 GPU Mali-450 (lima) et vidéo sur Le Potato : ce qui marche vraiment

Objectives

Leverage the Mali-450 MP5 GPU of the S905X under mainline Linux with the open-source lima driver (OpenGL ES 2 via Mesa), and understand what the board can actually display in video: HDMI 2.0 4K/60 for the interface, but no guaranteed hardware decoding.

Hardware

• The Potato AML-S905X-CC under Armbian/Debian mainline (kernel with lima, drivers/gpu/drm/lima)
• HDMI display (watch out for EDID/overscan quirks reported on the official hub)
• Multimedia alternative: LibreELEC AMLGX or CoreELEC, which include their own video stacks

Complete code

# 1) Verifier la presence du GPU mainline
ls /dev/dri/ 2>/dev/null
sudo dmesg | grep -i lima        # « lima 1000000.gpu » attendu

# 2) Installer la pile Mesa/lima et tester
sudo apt install mesa-utils-extra libegl1 libgles2
glmark2-es2                      # benchmark OpenGL ES 2

# 3) Lecture video : planifier un decodage LOGICIEL sous mainline
ffmpeg -hide_banner -hwaccels    # pas d'acceleration V4L2 Meson attendue
mpv --vo=gpu --gpu-context=drm --hwdec=no video.mp4

# 4) Pour du 4K fluide : passer par LibreELEC AMLGX ou CoreELEC
#    (leurs builds utilisent la pile video propre au projet)

Expected verification

dmesg shows the initialization of the lima driver and /dev/dri/renderD128 exists; glmark2-es2 returns a score of a few hundred points. When playing 1080p video under Armbian, CPU load remains high (htop) — a sign of software decoding.

Common errors

• Promising hardware-decoded 4K60 under Armbian: not confirmed.

• Expecting OpenGL 3 or ES 3: lima (Utgard architecture) provides OpenGL ES 2 only.
• No image on screen after login: known HDMI EDID/overscan quirk — try another display or adjust via armbian-config.
• Overheating during benchmarks: the SoC gets very hot without a heatsink.
• HDMI CEC: the pin is selected between CEC and GPIO via a jumper.