Running Qt in raspberry pi 3 (rpi3) vs raspberry pi 4 (rpi4)

njvf

Hello there,

Using raspbian buster lite, I have a native compilation of Qt 5.12.5 in rpi3 that works in rpi3b and rpi3b+ using the eglfs platform as default. I even successfully can run qml (qtdeclarative) and qtmultimedia examples as qmlvideo and qmlvideofx using gstreamer dependencies. So, the previous uses the following libraries (are loaded):

.../plugins/platforms/libqeglfs.so
.../plugins/egldeviceintegrations/libqeglfs-brcm-integration.so

Here is the thing, using the exact same procedure for compilation in rpi3, I did a successfully native compilation in the rpi4, and when running the same examples mentioned, in the terminal (with debug variables) I can see no errors, the same libraries mentioned are loaded correctly but nothing is displayed in the screen/tv. I tried setting the variable DISPLAY and is the same. Forcing the run with -platform eglfs is the same as not setting it. But running with -platform linuxfb (this use other libraries) is display in screen but with a very poor performance.

On the other hand, the sdcard using in the rpi3, I put it in the rpi4 and exactly the same happens.

Some observations:
For both cases (native compilation in rpi4 and using same sdcard from rpi3 in rpi4):

I had to disabled/comment in /boot/config.txt "dtoverlay=vc4-kms-v3d". Otherwise, when running the message "failed to add service - already in use?" is show in debug.
In /boot/config.txt, the "max_framebuffers=2", I tried with the values 2, 1 and commented it. Always the same.
gpu mem set to 256 MB.
Changing the hdmi cable connection from port 0 to 1 did nothing. This was a "just in case moment".

It seems that is something with EGL in the rpi4 or some configuration, but I have not idea what can be.

Some help and guidance will be very helpful.

In the case that more information is needed, I will reply ASAP.

Regards.

Edit 0:
Here is the same post in official forum:
https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=256670

Also here they talk about the same and give guidance about how to do it using cross compilation.
https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=244984

maxwell31

I have similar problems
https://forum.qt.io/topic/108730/running-a-qtquick-app-on-raspberrypi-4-problem-rendering-app-to-screen/2

njvf

Here is the same post in official forum:
https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=256670

Also here they talk about the same and give guidance about how to do it using cross compilation.
https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=244984

From the posts, the legacy proprietary driver is no more supported on the rpi4.
Currently, mesa drivers are needed for v3d to get acceleration and desktop is needed.

Some one has a an official or standard way to compile Qt for rpi4 to get acceleration?.
Like dependencies and mkspecs.

I'll try a native compilation using mesa and post about it.

Regards.