QTWebengine Browser Screen Tearing in i.MX6DL + etnaviv + mesa 19.2.6 + libdrm

Qt Webengine based Browser shows screen tearing effects:

• random small white triangles
• custom pieces of the visible webpage on an different position
• grey big circles
• flickering drop down menus
• false positioned drop down menus

The behavior can be provoked by multiple clicks on drop-down select menus, doesn't matter if really fast or "slow".

The rendered artifacts will not disappear immediately and only disappear after a click on the touchscreen or not.

Tried following settings:

• enabling/disabling VSYNC (FORCE_VSYNC, FB_MULTI_BUFFER=3 or more)
• Multibuffer support with increased framebuffer size
• increased buffer size in kernel
• various chromium flags did not help
• debugging opengl output does not bring up any errors

QTWEBENGINE_CHROMIUM_FLAGS=""--disable-gpu-compositing" seems to solve the issue for version 5.13.x based on Chromium 73!

Also tried on Chromium 77 Qt 5.14 from Yocto Qt Repository. This flag does not seems to help there anymore.

Used components for the system: i.MX6 DL / 1GB RAM / EGLFS etnaviv based

Build with Yocto Warrior.

meta-qt5: Chromium 69 based/ QT5.12.3 -> no problems !

SRCREV: 2a5f9415e48a38f6f4eb0cf375737a2d8438e2fe / git@github.com:meta-qt5/meta-qt5.git

meta-qt5: Chromium 73 based/ QT5.13.0 **  -> only works with mentioned flag, otherwise rendering issues

SRCREV: 12ea469918bcb73605b9c1e5080351f1189c0f17 / git@github.com:meta-qt5/meta-qt5.git

libdrm: v2.4.100/  http://www.linuxfromscratch.org/blfs/view/svn/x/libdrm.html

mesa: 19.2.6: 5836dd66e02654176a2c81c69a9c76436788fdb5 / git://github.com/mesa3d/mesa.git

ces-qt-browser: master HEAD / https://github.com/software-celo/ces-qt-browser

Linux: Kernel 4.19.17 LVDS output 1280x800

Please find attached:

• eglfs_kms configuration file
• environment for browser with graphic settings
• simple debug output of browser
• rendering failure white triangles rendering failure of snippets from the webpage

Try to verify the issue with Wayland (weston, libdrm, mesa 19.2.6, Qt 5.13.2) and try to revert various patches of QtWebengine and Chromium backend related to graphic system.

In my opinion the issue seems to be related to QtWebengine/Chromium.